U.S. patent application number 16/635329 was filed with the patent office on 2020-05-21 for super-abrasive grain and super-abrasive grinding wheel.
This patent application is currently assigned to Sumitomo Electric Industries, Ltd.. The applicant listed for this patent is Sumitomo Electric Industries, Ltd. A.L.M.T. Corp.. Invention is credited to Akito ISHII, Nobuhide NAKAMURA, Tomokazu NAKAMURA, Katsumi OKAMURA.
Application Number | 20200156213 16/635329 |
Document ID | / |
Family ID | 67548906 |
Filed Date | 2020-05-21 |
United States Patent
Application |
20200156213 |
Kind Code |
A1 |
ISHII; Akito ; et
al. |
May 21, 2020 |
SUPER-ABRASIVE GRAIN AND SUPER-ABRASIVE GRINDING WHEEL
Abstract
There is provided a super-abrasive grain including: a body
composed of cubic boron nitride or diamond; and a ceramic coating
film coating at least a portion of a surface of the body.
Inventors: |
ISHII; Akito; (Osaka-shi,
JP) ; OKAMURA; Katsumi; (Osaka-shi, JP) ;
NAKAMURA; Tomokazu; (Kato-shi, JP) ; NAKAMURA;
Nobuhide; (Kato-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sumitomo Electric Industries, Ltd.
A.L.M.T. Corp. |
Osaka-shi
Tokyo |
|
JP
JP |
|
|
Assignee: |
Sumitomo Electric Industries,
Ltd.
Osaka
JP
A.L.M.T. Corp.
Tokyo
JP
|
Family ID: |
67548906 |
Appl. No.: |
16/635329 |
Filed: |
December 6, 2018 |
PCT Filed: |
December 6, 2018 |
PCT NO: |
PCT/JP2018/044911 |
371 Date: |
January 30, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B 35/5831 20130101;
C09K 3/14 20130101; B24D 3/346 20130101; B24D 3/00 20130101; C04B
35/628 20130101 |
International
Class: |
B24D 3/34 20060101
B24D003/34 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 8, 2018 |
JP |
2018-020958 |
Claims
1. A super-abrasive grain comprising: a body composed of cubic
boron nitride or diamond; and a ceramic coating film coating at
least a portion of a surface of the body.
2. The super-abrasive grain according to claim 1, wherein the body
has a single-crystal structure.
3. The super-abrasive grain according to claim 1, wherein the body
has a polycrystalline structure.
4. The super-abrasive grain according to claim 1, wherein the
coating film has an average crystal grain size of 500 nm or
less.
5. The super-abrasive grain according to claim 4, wherein the
coating film has an average crystal grain size of 50 nm or
less.
6. The super-abrasive grain according to claim 1, wherein the
coating film contains one selected from the following (a) and (b):
(a) a nitride, a carbide, a carbonitride, an oxide, or an
oxynitride containing one or more elements selected from group 4
elements, group 5 elements and group 6 elements in the periodic
table, Al, Si, Y, Mg, and Ca; and (b) diamond-like carbon or
diamond.
7. The super-abrasive grain according to claim 1, wherein the
coating film is composed of (Ti.sub.1-xb1-yb1Si.sub.xb1M1.sub.yb1)
(C.sub.1-zb1N.sub.zb1), or (Al.sub.1-xb2M2.sub.xb2)
(C.sub.1-zb2N.sub.zb2), where M1=one or more elements selected from
group 4 elements, group 5 elements and group 6 elements in the
periodic table, and Al (Note that Ti is excluded), xb1=0 or more
and 0.45 or less, yb1=0 or more and 0.5 or less, zb1=0.2 or more
and 0.5 or less, and M2=one or more elements selected from group 4
elements, group 5 elements and group 6 elements in the periodic
table, and Si, xb2=0.025 or more and 0.475 or less, zb2=0.2 or more
and 0.5 or less.
8. The super-abrasive grain according to claim 1, wherein the
coating film has a thickness of 1 nm or more and 5000 nm or
less.
9. The super-abrasive grain according to claim 1, wherein the
coating film has a multilayer structure composed of a plurality of
stacked ceramic layers.
10. The super-abrasive grain according to claim 1, further
comprising an insulating film covering an outer surface of the
coating film.
11. The super-abrasive grain according to claim 10, wherein the
insulating film includes a compound of any one of an oxide and an
oxynitride containing one or more elements selected from Al, Si,
Zr, and Ti.
12. The super-abrasive grain according claim 10, wherein the
insulating film has a thickness of 1 nm or more and 5000 nm or
less.
13. The super-abrasive grain according to claim 1, wherein the body
has a grain size of 1 .mu.m or more and 600 .mu.m or less.
14. A super-abrasive grinding wheel comprising: a disk-shaped
substrate; and a super-abrasive grain layer covering at least an
outer peripheral surface of the substrate, the super-abrasive grain
layer having the super-abrasive grain according to claim 1.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to super-abrasive grains and
a super-abrasive grinding wheel. This application claims priority
based on Japanese Patent Application No. 2018-020958 filed on Feb.
8, 2018. The entire contents of the description of the Japanese
patent application are incorporated herein by reference.
BACKGROUND ART
[0002] A super-abrasive tool (a wheel) of PTL 1 is known as a tool
used for precision processing. This super-abrasive tool includes a
disk-shaped substrate and an abrasive grain layer formed on an
outer peripheral portion of the substrate. The abrasive grain layer
includes super-abrasive grains (diamond abrasive grains, cubic
boron nitride abrasive grains or the like) and a bonding material
which bonds the super-abrasive grains and fixes the super-abrasive
grains to the outer peripheral portion of the substrate.
CITATION LIST
Patent Literature
[0003] PTL 1: Japanese Patent Laying-Open No. 2002-137168
SUMMARY OF INVENTION
[0004] According to the present disclosure, a super-abrasive grain
comprises:
[0005] a body composed of cubic boron nitride or diamond; and
[0006] a ceramic coating film coating at least a portion of a
surface of the body.
[0007] According to the present disclosure, a super-abrasive
grinding wheel comprises:
[0008] a disk-shaped substrate; and
[0009] a super-abrasive grain layer covering at least an outer
peripheral surface of the substrate,
[0010] the super-abrasive grain layer having super-abrasive grains
according to the present disclosure.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a schematic cross section of a super-abrasive
grain according to an embodiment.
[0012] FIG. 2 is an enlarged cross section of a portion of the
super-abrasive grain shown in FIG. 1 that is surrounded by a circle
drawn with a broken line.
[0013] FIG. 3 is a schematic perspective view of a super-abrasive
grinding wheel according to an embodiment.
[0014] FIG. 4 is a cross section of the super-abrasive grinding
wheel shown in FIG. 3 taken along a line (IV)-(IV).
[0015] FIG. 5 is an enlarged cross section of a portion of the
super-abrasive grinding wheel shown in FIG. 4 that is surrounded by
a circle drawn with a broken line.
DETAILED DESCRIPTION
Problem to be Solved by the Present Disclosure
[0016] The above super-abrasive grain layer includes super-abrasive
grains that are per se (or their bodies are) bare abrasive grains
and are thus susceptible to large stress from a workpiece.
Therefore, the abrasive grains may be fractured or similarly
damaged.
[0017] Accordingly, it is one object to provide a super-abrasive
grain having a body which is not easily damaged.
[0018] Another object is to provide a super-abrasive grinding wheel
having a high grinding ratio.
Advantageous Effect of the Present Disclosure
[0019] The super-abrasive grain described above has a body which is
not easily damaged.
[0020] The super-abrasive grinding wheel has a high grinding
ratio.
DESCRIPTION OF EMBODIMENTS
[0021] Initially, embodiments of the present disclosure will be
enumerated and specifically described.
[0022] (1) A super-abrasive grain in one aspect of the present
disclosure comprises:
[0023] a body composed of cubic boron nitride or diamond; and
[0024] a ceramic coating film coating at least a portion of a
surface of the body.
[0025] According to the above configuration, the body of the
abrasive grain is not easily damaged. This is because the coating
film coating at least a portion of the surface of the body of the
abrasive grain helps to alleviate an impactive force experienced by
the body of the abrasive grain as it is brought into contact with a
workpiece. Thus the body of the abrasive grain is not easily
cracked and thus does not easily provide a fracture starting point,
and in addition, if it should be cracked it is not easily further
cracked. A grinding tool (grindstone) such as a super-abrasive
grinding wheel having a high grinding ratio can thus be
constructed. Note that a grinding ratio is "the volume of the
workpiece ground away/the total worn volume of super-abrasive
grains."
[0026] (2) As one form of the above super-abrasive grain,
[0027] the body of the abrasive grain has a single-crystal
structure.
[0028] The above configuration helps to enhance the body per se of
the abrasive grain in strength, as compared with an abrasive grain
having a body having a polycrystalline structure.
[0029] (3) As one form of the above super-abrasive grain,
[0030] the body of the abrasive grain has a polycrystalline
structure.
[0031] According to the above configuration, even when the abrasive
grain has a body having a polycrystalline structure, including the
coating film helps to provide a grinding ratio increased as
compared with that provided in the case of an abrasive grain having
a body having a single-crystal structure.
[0032] (4) As one form of the above super-abrasive grain,
[0033] the coating film has an average crystal grain size of 500 nm
or less.
[0034] According to the above configuration, the coating film has a
small average crystal grain size and hence large strength, and thus
helps to suppress damage to the coating film per se that is caused
by an impactive force (or stress) caused as the abrasive grain is
brought into contact with a workpiece. This helps to alleviate
impactive force exerted to the body of the abrasive grain as it is
brought into contact with the workpiece.
[0035] (5) As one form of the above super-abrasive grain,
[0036] the coating film has an average crystal grain size of 50 nm
or less.
[0037] According to the above configuration, the coating film has a
further smaller average crystal grain size, and can further be
enhanced in strength.
[0038] (6) As one form of the above super-abrasive grain,
[0039] the coating film includes one selected from the following
(a) and (b):
[0040] (a) a nitride, a carbide, a carbonitride, an oxide, or an
oxynitride containing one or more elements selected from group 4
elements, group 5 elements and group 6 elements in the periodic
table, Al, Si, Y, Mg, and Ca; and
[0041] (b) diamond-like carbon or diamond.
[0042] According to the above configuration, the coating film is
high in hardness and excellently wear-resistant, and thus helps to
suppress damage to the body of the abrasive grain.
[0043] (7) As one form of the above super-abrasive grain, the
coating film is composed of (Ti.sub.1-xb1-yb1Si.sub.xb1M1.sub.yb1)
(C.sub.1-zb1N.sub.zb1) or (Al.sub.1-xb2M2.sub.xb2)
(C.sub.1-zb2N.sub.zb2).
[0044] M1=one or more elements selected from group 4 elements,
group 5 elements and group 6 elements in the periodic table, and Al
(Note that Ti is excluded),
[0045] xb1=0 or more and 0.45 or less,
[0046] yb1=0 or more and 0.5 or less,
[0047] zb1=0.2 or more and 0.5 or less, and
[0048] M2=one or more elements selected from group 4 elements,
group 5 elements and group 6 elements in the periodic table, and
Si,
[0049] xb2=0.025 or more and 0.475 or less,
[0050] zb2=0.2 or more and 0.5 or less.
[0051] The above configuration enables particularly excellent
wear-resistance.
[0052] (8) As one form of the above super-abrasive grain, the
coating film has a thickness of 1 nm or more and 5000 nm or
less.
[0053] When the coating film has a thickness of 1 nm or more, it
helps to enhance the coating film per se in strength and hence
suppress damage to the coating film. This helps to suppress damage
to the body of the abrasive grain. When the coating film has a
thickness of 5000 nm or less, the coating film does not have an
excessively large thickness and thus does not easily peel off, and
a state with the coating film formed on an outer periphery of the
body of the abrasive grain is easily maintained.
[0054] (9) As one form of the above super-abrasive grain, the
coating film has a multilayer structure composed of a plurality of
stacked ceramic layers.
[0055] According to the above configuration, the multilayer
structure allows each layer's residual stress to be increased, and
thus allows the coating film to be high in hardness and helps to
enhance an effect to suppress damage to the coating film.
[0056] (10) As one form of the above super-abrasive grain, it
further comprises an insulating film covering an outer surface of
the coating film.
[0057] According to the above configuration, super-abrasive grains
are easily fixed to an outer peripheral surface of a substrate of a
super-abrasive grinding wheel through electroplating. That is, a
plating film is easily used as a bonding material to fix
super-abrasive grains to the outer peripheral surface of the
substrate of the super-abrasive grinding wheel. This is because the
insulating film does not allow the plating film to easily grow on a
surface of the insulating film and excessive reduction of the
grinding ratio can be suppressed by the plating film.
[0058] (11) As one form of the above super-abrasive grain, the
insulating film includes a compound of any one of an oxide and an
oxynitride containing one or more elements selected from Al, Si,
Zr, and Ti.
[0059] According to the above configuration, the insulating film
has an excellent insulating property, and super-abrasive grains are
easily fixed to the outer peripheral surface of the substrate of
the super-abrasive grinding wheel through electroplating.
[0060] (12) As one form of the above super-abrasive grain, the
insulating film has a thickness of 1 nm or more and 5000 nm or
less.
[0061] The insulating film having a thickness of 1 nm or more has
its insulating performance easily enhanced. The insulating film
having a thickness of 5000 nm or less is not excessively large in
thickness and it does not easily peel off, and it is easy to
maintain a state in which the insulating film is formed on the
outer surface of the coating film.
[0062] (13) As one form of the above super-abrasive grain, the body
of the abrasive grain has a grain size of 1 .mu.m or more and 600
.mu.m or less.
[0063] The abrasive grain having a body with a grain size of 1
.mu.m or more is not excessively small and thus facilitates
grinding a workpiece and in addition, it is also easily handled and
hence facilitates constructing a super-abrasive grinding wheel
described hereinafter. The abrasive grain having a body with a
grain size of 600 .mu.m or less is not excessively large and thus
not easily fractured or similarly damaged due to an impactive force
exerted to the body of the abrasive grain as it is brought into
contact with a workpiece.
[0064] (14) A super-abrasive grinding wheel in one aspect of the
present disclosure comprises:
[0065] a disk-shaped substrate; and
[0066] a super-abrasive grain layer covering at least an outer
peripheral surface of the substrate,
[0067] the super-abrasive grain layer having the super-abrasive
grain according to any one of items (1) to (13) above.
[0068] According to the above configuration, a super-abrasive grain
having a body not easily damaged is comprised, and a high grinding
ratio can be achieved.
[0069] <<Detailed Description of Embodiments of the Present
Disclosure>>
[0070] Details of embodiments of the present disclosure will be
described below with reference to the drawings.
[0071] [Super-Abrasive Grain]
[0072] A super-abrasive grain 1 according to an embodiment will be
described mainly with reference to FIGS. 1 and 2 (and FIG. 3 to
FIG. 5 where appropriate). Super-abrasive grain 1 is a member used
to grind a workpiece, and includes a body 2 and a coating film 3
coating a surface of body 2 of the abrasive grain. One feature of
super-abrasive grain 1 is that coating film 3 has a specific
structure. Details will be described below.
[0073] [Body of Abrasive Grain]
[0074] Body 2 of the abrasive grain is formed of cubic boron
nitride (cBN) or diamond.
[0075] Body 2 of the abrasive grain has a single-crystal or
polycrystalline structure. Body 2 of the abrasive grain has a grain
size preferably of 1 .mu.m or more and 600 .mu.m or less. Abrasive
grain having body 2 with a grain size of 1 .mu.m or more is not
excessively small, and thus facilitates grinding a workpiece and in
addition, it is also easily handled and hence facilitates
constructing a super-abrasive grinding wheel 10 (see FIGS. 3-5) and
other similar grinding tools (or grindstone). An abrasive grain
having body 2 with a grain size of 600 .mu.m or less is not
excessively large and thus not easily fractured or similarly
damaged due to an impactive force (or stress) experienced by body 2
of the abrasive grain as it is brought into contact with a
workpiece. Body 2 of the abrasive grain more preferably has a grain
size of 10 .mu.m or more and 300 .mu.m or less, and particularly
preferably 20 .mu.m or more and 200 .mu.m or less. When body 2 of
the abrasive grain has a single-crystal structure, the grain size
of body 2 of the abrasive grain can also be referred to as a
crystal grain size. The grain size of body 2 of the abrasive grain
is an average grain size when there are a plurality of abrasive
grains 1, such as super-abrasive grinding wheel 10 described later
has. When body 2 of the abrasive grain has a polycrystalline
structure, the average crystal grain size is preferably 100 nm or
more and 6000 nm or less, more preferably 200 nm or more and 4000
nm or less, and particularly preferably 300 nm or more and 2000 nm
or less.
[0076] Compositional analysis can be performed by energy dispersive
x-ray (EDS) analysis. Structural analysis can be performed by x-ray
diffraction (for measurement of peak intensity) or scanning
transmission electron microscopic (STEM) observation. The grain
size of body 2 of the abrasive grain is determined by (average
grain size of super-abrasive grains 1)-(thickness of coating film
3+thickness of insulating film 4).times.2. The average grain size
of super-abrasive grains 1 is measured with a laser diffraction
type particle size distribution analyzer (for example, the SALD
series manufactured by Shimadzu Corporation). The thickness of
coating film 3 and that of insulating film 4 are measured in a
measurement method described hereinafter. The average crystal grain
size of bodies 2 of the abrasive grains is determined from cross
sections of bodies 2 of the abrasive grains exposed by FIB (focused
ion beam), as obtained from an HAADF (high-angle annular dark
field)-STEM image obtained through an STEM (JEM-ARM200F Dual-X
Nippon produced by JEOL Ltd.). From a difference in contrast of
each crystal grain in the HAADF-STEM image, the cross-sectional
area of each crystal grain is derived by image analysis software,
and the diameter of a circle having an area equal to that
cross-sectional area (or an equivalent circle diameter) is
determined. An average value of the equivalent circle diameters of
ten or more crystal grains is taken as the average crystal grain
size of bodies 2 of the abrasive grains.
[0077] [Coating Film]
[0078] Coating film 3 coats at least a portion of the surface of
body 2 of each abrasive grain and alleviates an impactive force (or
stress) experienced by body 2 of the abrasive grain as it is
brought into contact with the workpiece. Coating film 3 is formed
to coat substantially the entire surface of body 2 of the abrasive
grain in this example. By including coating film 3, body 2 of the
abrasive grain is not easily cracked and thus does not easily
provide a fracture starting point, and in addition, if it should be
cracked it is not easily further cracked. Body 2 is thus not easily
damaged, and super-abrasive grinding wheel 10 having a high
grinding ratio can be constructed.
[0079] Note that a grinding ratio is "the volume of a workpiece
ground away/the total worn volume of super-abrasive grains." The
volume of the workpiece ground away is determined from the
difference in volume between the workpiece before being ground and
the workpiece after being ground. The super-abrasive grains' total
worn volume is determined as follows: By grinding a carbon plate by
the super-abrasive grinding wheel before and after a grinding
process, undulations of an abrasive surface of the super-abrasive
grinding wheel to which the super-abrasive grains are fixed are
transferred to the carbon plate. When grinding the carbon plate,
the super-abrasive grinding wheel is rotated to cut into the carbon
plate without moving the carbon plate. The cross-sectional shape of
the undulations of each carbon plate transferred before and after
the grinding process is measured with a stylus type surface
roughness meter in a direction perpendicular to a direction in
which the super-abrasive grinding wheel rotates. Two
cross-sectional shapes obtained before and after the grinding
process are compared to determine the reduced area. Let "(the
reduced area).times.(the diameter of the super-abrasive grinding
wheel)" be the total worn volume of super-abrasive grains 1. The
removed amount in volume is determined by the product of the
cutting depth and the length and thickness of the workpiece.
Material's removed amount in volume is represented by a horizontal
axis and a worn amount is represented by a vertical axis to plot a
change, and therefrom a linear function of the change is determined
by the method of least squares to calculate a gradient. This is
used to calculate the super-abrasive grains' total worn volume for
any removed amount in volume.
[0080] (Material)
[0081] Coating film 3 is a ceramic coating film. Specific ceramics
include one selected from the following (a) and (b). This allows
body 2 not to be easily damaged. This is because coating film 3 of
the following materials is high in hardness and excellently
wear-resistant.
[0082] (a) a nitride, a carbide, a carbonitride, an oxide, or an
oxynitride containing one or more elements selected from group 4
elements, group 5 elements and group 6 elements in the periodic
table, aluminum (Al), silicon (Si), yttrium (Y), magnesium (Mg),
and calcium (Ca), and (b) diamond-like carbon or diamond
[0083] The group 4 elements in the periodic table are titanium
(Ti), zirconium (Zr) and hafnium (Hf). The group 5 elements in the
periodic table are vanadium (V), niobium (Nb) and tantalum (Ta).
The group 6 elements in the periodic table are chromium (Cr),
molybdenum (Mo) and tungsten (W).
[0084] The ceramic's composition is particularly preferably
(Ti.sub.1-xb1-yb1Si.sub.xb1M1.sub.yb1) (C.sub.1-zb1N.sub.zb1), or
(Al.sub.1-xb2M2.sub.xb2) (C.sub.1-zb2N.sub.zb2). This helps to
further suppress damage to body 2 of the abrasive grain. This is
because coating film 3 satisfying these compositions is
particularly excellently wear-resistant.
[0085] M1=one or more elements selected from group 4 elements,
group 5 elements and group 6 elements in the periodic table, and Al
(Note that Ti is excluded),
[0086] xb1=0 or more and 0.45 or less,
[0087] yb1=0 or more and 0.5 or less,
[0088] zb1=0.2 or more and 0.5 or less, and
[0089] M2=one or more elements selected from group 4 elements,
group 5 elements and group 6 elements in the periodic table, and
Si,
[0090] xb2=0.025 or more and 0.475 or less,
[0091] zb2=0.2 or more and 0.5 or less.
[0092] The nitride typically contains two of the above elements,
and in addition, includes nitrides containing three of the above
elements. Specifically, nitrides containing two of the above
elements include nitrides containing: one element selected from Zr,
Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si; and Ti. More specifically,
the nitrides containing two of the above elements include TiVN,
TiCrN, TiZrN, TiNbN, TiMoN, TiHfN, TiTaN, TiWN, TiAlN, and TiSiN.
Another nitride containing two of the above elements includes
AlCrN. Specifically, the nitrides containing three of the above
elements include nitrides containing: one element selected from Zr,
Nb, Ta, and Si; Ti; and Al. More specifically, the nitrides
containing three of the above elements include TiAlZrN, TiAlNbN,
TiAlTaN, and TiAlSiN. Among these nitrides, TiAlN, AlCrN and
TiAlSiN are particularly preferable. It is because they are
particularly excellently wear resistant.
[0093] As the above carbide and the above carbonitride, as well as
the above nitride, carbides and carbonitrides containing two of the
above elements are representative. That is, carbides and
carbonitrides containing: one element selected from Zr, Hf, V, Nb,
Ta, Cr, Mo, W, Al and Si; and Ti can be referred to. More
specifically, the above carbides include TiVC, TiCrC, TiZrC, TiNbC,
TiMoC, TiHfC, TiTaC, TiWC, TiAlC, and TiSiC. More specifically, the
above carbonitrides include TiVCN, TiCrCN, TiZrCN, TiNbCN, TiMoCN,
TiHfCN, TiTaCN, TiWCN, TiAlCN, and TiSiCN.
[0094] Specifically, the above oxide includes oxides containing:
one element selected from Ti, Cr, Zr, Hf, Ta, W, Al, and Si. More
specifically, the above oxides include TiO.sub.2, Cr.sub.2O.sub.3,
ZrO.sub.2, HfO.sub.2, Ta.sub.2O.sub.5, WO.sub.3, Al.sub.2O.sub.3,
and SiO.sub.2.
[0095] Specifically, the above oxynitride includes SiAlON.
[0096] Compositional analysis of coating film 3 can be performed by
EDS analysis, similarly as done for the composition analysis of
body 2 of the abrasive grain.
[0097] (Structure and Average Grain Size)
[0098] The structure of coating film 3 is, for example, a
polycrystalline structure. It is preferable that coating film 3 has
an average crystal grain size of 500 nm or less. Coating film 3
thus having a small average crystal grain size can be high in
strength. This facilitates suppressing damage to coating film 3
itself that is caused by impactive force (or stress) caused as the
abrasive grain is brought into contact with a workpiece, and in
addition, also facilitates alleviating an impactive force
experienced by body 2 of the abrasive grain as it is brought into
contact with the workpiece. Body 2 is thus not easily damaged. The
smaller the average crystal grain size of coating film 3 is, the
higher the strength of coating film 3 itself can be, and 200 nm or
less is preferable, and 50 nm or less is particularly preferable.
The average crystal grain size of coating film 3 is preferably 1 nm
or more.
[0099] The average crystal grain size of coating film 3 is
determined from a HAADF-STEM image through STEM. In observing a
HAADF-STEM image of the coating film, when coating film 3 has a
thickness of 100 nm or more, coating film 3 is mechanically
polished and subjected to Ar-ion milling to have a thickness of 100
nm or less. The STEM's magnification is set to 6.5 million times
and thus used to observe the HAADF-STEM image of coating film 3 in
ten or more areas in which an atomic arrangement can be observed.
One area where the atomic arrangement can be observed is taken as
one crystal grain. In a HAADF-STEM image, a crystal grain different
in crystal orientation is unobservable, and an area where an atomic
arrangement is observed can be regarded as a crystal grain. An
average grain size of the ten or more crystal grains is taken as an
average crystal grain size of coating film 3. In doing so, an
equivalent circle diameter of one area where the atomic arrangement
can be observed is taken as one crystal grain size.
[0100] (Structure)
[0101] Coating film 3 may have a monolayer structure composed of
the above ceramics, or may be a multilayer structure (see FIG. 2)
in which a plurality of layers composed of the above ceramics are
stacked. Coating film 3 having a multilayer structure allows each
layer's residual stress to be increased as compared with the
coating film having a monolayer structure, and can thus be high in
hardness and thus resistant to damage thereto. This helps to
suppress damage to body 2 of the abrasive grain. When coating film
3 has a multilayer structure, it may have two or three layers for
example. In that case, adjacent layers may be formed of different
ceramics. For example, when coating film 3 has a three-layer
structure (see FIG. 2), with a first layer 31 to a third layer 33
disposed sequentially from the side of body 2 of the abrasive grain
outwards, with second layer 32 composed of a material different
from that of first layer 31 and that of third layer 33, first layer
31 and third layer 33 may be composed of identical materials or
different materials (that is, the three layers may be composed
respectively of different materials). The structure of coating film
3 can be analyzed through a cross-sectional observation with an
STEM.
[0102] (Thickness)
[0103] Coating film 3 preferably has a thickness of 1 nm or more
and 5000 nm or less. When coating film 3 has a thickness of 1 nm or
more, it helps to enhance coating film 3 per se in strength and
hence suppress damage to coating film 3. When coating film 3 has a
thickness of 5000 nm or less, coating film 3 does not have an
excessively large thickness and thus does not easily peel off, and
a state with coating film 3 formed on an outer periphery of body 2
of the abrasive grain is easily maintained. The thickness of
coating film 3 is more preferably 10 nm or more and 2500 nm or
less, and particularly preferably 100 nm or more and 1000 nm or
less. When coating film 3 has a multilayer structure as described
above, the thickness of coating film 3 is the sum of each layer in
thickness. When coating film 3 has a multilayer structure, each
layer may be similar or different in thickness.
[0104] The thickness of coating film 3 is determined by
"{(equivalent circular diameter of super-abrasive grain
1)-(equivalent circular diameter of body 2 of the abrasive
grain)}/2." The equivalent circle diameter of super-abrasive grain
1 and that of body 2 of the abrasive grain are determined as
follows: in a cross section of super-abrasive grain 1,
super-abrasive grain 1 and body 2 of the abrasive grain have their
respective contours determined, and a diameter of a circle having
the same area as an area S surrounded by each contour is determined
as the equivalent circular diameter. That is, the equivalent
circular diameter is represented as 2.times.{area S inside the
contour/.pi.}.sup.1/2. For a plurality of super-abrasive grains 1,
the equivalent circle diameter of super-abrasive grains 1 and that
of bodies 2 of the abrasive grains are each an average of
equivalent circle diameters obtained from 30 or more super-abrasive
grains 1 in cross section.
[0105] The cross section of super-abrasive grain 1 is exposed as
follows: A molded body in which super-abrasive grains 1 are buried
in epoxy resin is produced. The content of super-abrasive grains 1
in the molded body is 50% by volume or more with respect to the
resin. The shape of the molded body is a rectangular parallelepiped
or a cube. The molded body is subjected to a CP (cross section
polisher) process. This process is performed in two stages. In a
first stage of the process, the molded body has any surface
processed until a cross section of at least one super-abrasive
grain 1 is visible. Once the cross section of super-abrasive grain
1 has been confirmed, then, as a second stage of the process, the
surface is further processed by 50% of the average grain size of
super-abrasive grains 1. The average grain size of super-abrasive
grains 1 is a value as measured with a laser diffraction type
particle size distribution analyzer, as has been described
above.
[0106] The cross section of the molded body is observed, and an
equivalent circle diameter of super-abrasive grain 1 and that of
body 2 of the abrasive grain are determined. The cross-sectional
observation is performed using a scanning electron microscope
(SEM), energy dispersive x-ray analysis (EDX), electron backscatter
diffraction (EBSD) analysis, or the like. Body 2 of the abrasive
grain, coating film 3 and the resin portion are separated through
an image analyzing binarization process. From an image obtained
therefrom, the area in cross section of super-abrasive grain 1 and
that of body 2 of the abrasive grain are derived and the equivalent
circle diameter of super-abrasive grain 1 and that of body 2 of the
abrasive grain are determined.
[0107] (Coating Method)
[0108] While coating film 3 is formed on the surface of body 2 of
the abrasive grain by physical vapor deposition such as an arc ion
plating (AIP) method, a HIPIMS (High Power Impulse Magnetron
Sputtering) method, an arc plasma powder method or the like, it is
optimally formed for example in the arc plasma powder method. The
coating is applied under conditions including a discharge voltage
of 10 V or more and 200 V or less, a discharge frequency of 1 Hz or
more and 20 Hz or less, a capacitor having a capacitance of 360 g
or more and 1800 g or less, a shot count of 1000 or more and
10,000,000 or less, and a heat treatment temperature of 100.degree.
C. or higher and 2000.degree. C. or lower. In particular, lower
heat treatment temperature facilitates forming a coating film
having a small average crystal grain size. For example, a heat
treatment temperature of 1000.degree. C. or lower helps to provide
a coating film having an average crystal grain size of 500 nm or
less, and a heat treatment temperature of 200.degree. C. or lower
helps to provide a coating film having an average crystal grain
size of 50 nm or less. The coating film is easily reduced in
thickness by reducing a period of time of coating, and a coating
time of 150 hrs or less (for bodies 2 having a mass of 10 g) allows
the coating film to have a thickness of 1 nm or more and 5000 nm or
less.
[0109] [Insulating Film]
[0110] Super-abrasive grain 1 may further include an insulating
film 4 covering an outer surface of coating film 3 (see FIGS. 1 and
2). This facilitates fixing super-abrasive grains 1 to an outer
peripheral surface 111 (see FIG. 4) of a substrate 11 of
super-abrasive grinding wheel 10 (see FIG. 3 and FIG. 4) through
electroplating. That is, it facilitates using a plating film as a
bonding material 13 (see FIG. 5) for fixing super-abrasive grains 1
on outer peripheral surface 111 of substrate 11. This is because
insulating film 4 does not allow the plating film to easily grow on
a surface of insulating film 4 and excessive reduction of the
grinding ratio can be suppressed by the plating film.
[0111] (Material)
[0112] Insulating film 4 is preferably formed of a material
including a compound of an oxide or oxynitride containing one or
more elements selected from Al, Si, Zr, and Ti. These materials are
excellently insulating, and super-abrasive grains 1 are easily
fixed to outer peripheral surface 111 (see FIG. 4) of substrate 11
of super-abrasive grinding wheel 10 through electroplating.
Specifically, insulating film 4 is formed of material including,
Al.sub.2O.sub.3, ZrO.sub.2, SiAlON, and the like. A compositional
analysis of insulating film 4 can be performed by EDS analysis,
similarly as done for the compositional analysis of coating film
3.
[0113] (Thickness)
[0114] Insulating film 4 preferably has a thickness of 1 nm or more
and 5000 nm or less. When insulating film 4 has a thickness of 1 nm
or more, it helps to enhance insulation. Insulating film 4 having a
thickness of 5000 nm or less is not excessively large in thickness
and it does not easily peel off, and it is easy to maintain a state
in which insulating film 4 is formed on the outer surface of
coating film 3. The thickness of insulating film 4 is more
preferably 100 nm or more and 2000 nm or less, and particularly
preferably 200 nm or more and 1000 nm or less.
[0115] When insulating film 4 is provided, the thickness of coating
film 3 of super-abrasive grain 1 is determined by {(equivalent
circle diameter of outer periphery of coating film 3)-(equivalent
circle diameter of body 2 of the abrasive grain)}/2, and the
thickness of insulating film 4 of super-abrasive grain 1 is
determined by {(equivalent circle diameter of super-abrasive grain
1)-(equivalent circle diameter of outer periphery of coating film
3)}/2. How the equivalent circle diameter of super-abrasive grain 1
and the equivalent circle diameter of body 2 of the abrasive grain
are determined is as has been described above. The equivalent
circle diameter of the outer periphery of coating film 3 is the
equivalent circle diameter of a boundary portion between coating
film 3 and insulating film 4 and let it be a diameter of a circle
having the same area as a total cross sectional area of coating
film 3 and body 2 of the abrasive grain. A transparent sheet is
placed on the image of the cross section, and the observer traces
an interface between coating film 3 and insulating film 4 and fills
in only the area inside the interface (i.e., the area of coating
film 3 and body 2 of the abrasive grain) with black. Image analysis
software is used to subject the black portion and the white portion
to binarization to divide the image and a total cross-sectional
area of coating film 3 and body 2 of the abrasive grain is derived
therefrom. The diameter of a circle having the same area as the
total cross-sectional area is determined, and the equivalent circle
diameter of the outer periphery of coating film 3 is determined.
The interface between coating film 3 and insulating film 4 can also
be extracted by image analysis software from a difference in
contrast between coating film 3 and insulating film 4 or the
like.
[0116] (Covering Method)
[0117] Insulating film 4 can be formed by the arc plasma powder
method, similarly as done to form coating film 3.
[0118] [Application]
[0119] Super-abrasive grain 1 according to an embodiment is
suitably applicable as abrasive grains for a grinding tool
(grindstone), such as a super-abrasive grinding wheel.
[0120] [Function and Effect]
[0121] Super-abrasive grain 1 according to the embodiment has
coating film 3 large in strength coating the surface of body 2 of
the abrasive grain and thus does not easily transmit to body 2 of
the abrasive grain an impactive force caused as the abrasive grain
is brought into contact with a workpiece, and thus body 2 is not
easily damaged. A grindstone having a high grinding ratio can thus
be constructed.
[0122] [Super-Abrasive Grinding Wheel]
[0123] Super-abrasive grinding wheel 10 according to an embodiment
will be described mainly with reference to FIGS. 3 to 5.
Super-abrasive grinding wheel 10 includes a disk-shaped substrate
11 and a super-abrasive grain layer 12 covering an outer peripheral
surface 111 (see FIG. 4) of substrate 11.
[0124] [Substrate]
[0125] Substrate 11 is formed of material including Al and an Al
alloy, iron and an iron alloy, carbon tool steel, high speed tool
steel, alloy tool steel, cemented carbide, cermet and the like.
Substrate 11 can have a size (inner and outer diameters and
thickness) selectable as appropriate depending for example on the
size of a machine tool such as a machining center on which
super-abrasive grinding wheel 10 is installed, that is, depending
on the size of the workpiece. Substrate 11 can be a substrate for a
known super-abrasive grinding wheel.
[0126] [Super-Abrasive Grain Layer]
[0127] Super-abrasive grain layer 12 in this example is formed to
cover front and back and outer peripheral end surfaces of outer
peripheral surface 111 of substrate 11 continuously (see FIGS. 3
and 4). Super-abrasive grain layer 12 can be selected in size
(thickness and width), as appropriate, depending on the size
(thickness and width) of substrate 11. The thickness refers to a
length in the axial direction of super-abrasive grinding wheel 10,
and the width refers to a length in the radial direction of
super-abrasive grinding wheel 10. Super-abrasive grain layer 12
includes super-abrasive grains 1 and bonding material 13 (see FIG.
5).
[0128] (Super-Abrasive Grain)
[0129] Super-abrasive grain 1 is as has been discussed above. There
may be provided a plurality of super-abrasive grains 1.
Super-abrasive grain layer 12 on the side of its front surface has
super-abrasive grains 1 partially exposed from bonding material 13
to provide a cutting edge portion for grinding a workpiece. In
contrast, super-abrasive grain layer 12 on the side of substrate 11
has super-abrasive grains 1 all buried in bonding material 13.
Super-abrasive grains 1 that are buried are partially exposed and
thus grind the workpiece during a process in which while the
workpiece is ground by super-abrasive grinding wheel 10
super-abrasive grains 1 on the side of the front surface of
super-abrasive grain layer 12 are worn and fall off and bonding
material 13 are also worn. The plurality of super-abrasive grains 1
may have their respective bodies 2 identically configured (i.e.,
identical in material, equal in size and the like) and their
respective coating films 3 identically configured (i.e., identical
in material, equal in thickness and the like), or some
super-abrasive grains 1 may have body 2 and coating film 3
different in configuration (i.e., material, size, and the like)
than other super-abrasive grains 1. For example, some
super-abrasive grains 1 may have their bodies 2 composed of cBN and
other super-abrasive grains 1 may have their bodies 2 composed of
diamond, and some and other super-abrasive grains 1 may have their
respective coating films 3 identically configured (i.e., identical
in material, and equal in thickness and grain size).
[0130] The average grain size of super-abrasive grains 1 is
determined by dissolving bonding material 13 of super-abrasive
grain layer 12 with acid or the like to remove super-abrasive
grains 1 and measuring the removed super-abrasive grains 1 with a
laser diffraction type particle size distribution analyzer. When
super-abrasive grain layer 12 is large, super-abrasive grain layer
12 is cut off by a predetermined volume (for example of 0.5
cm.sup.3), and from the cut portion, super-abrasive grains 1 are
removed by dissolving bonding material 13. The average grain size
of bodies 2 of the abrasive grains are determined as follows:
super-abrasive grains 1 have coating film 3, insulating film 4 and
the like dissolved together with bonding material 13 to have their
bodies 2 alone removed therefrom and measured with a laser
diffraction type particle size distribution analyzer.
Alternatively, coating film 3 and insulating film 4 are not
dissolved and bonding material 13 is alone dissolved to remove
super-abrasive grains 1 and the average grain size of bodies 2 may
be determined by "(average grain size of super-abrasive grains
1)-(thickness of coating film 3+thickness of insulating film
4).times.2," as has been set forth above.
[0131] (Bonding Material)
[0132] Bonding material 13 fixes super-abrasive grains 1 to outer
peripheral surface 111 (FIG. 4). Bonding material 13 includes in
type one type selected from resin bond, metal bond, vitrified bond,
electroplating bond and a combination thereof, or metal wax, for
example. As these bonds and metal wax can be known bonds and metal
wax. For example, the resin bond includes as a main component a
thermosetting resin such as phenol resin, epoxy resin, and
polyimide resin. The metal bond includes as a main component an
alloy containing copper, tin, iron, cobalt, or nickel. The
vitrified bond may include a vitreous material as a main component.
The electroplating bond includes nickel plating. The metal wax
includes silver (Ag) wax and the like. The type of bonding material
13 can be appropriately selected depending on what material coating
film 3 of super-abrasive grain 1 is made of, whether insulating
film 4 is present or absent, and the like. For example, when
coating film 3 of super-abrasive grain 1 is electrically conductive
but does not have insulating film 4, then, as bonding material 13,
electroplating bond is excluded and resin bond, metal bond,
vitrified bond, and metal wax can be used. When coating film 3 of
super-abrasive grain 1 has an insulating property or has insulating
film 4 regardless of what material coating film 3 is made of, all
the above bonds including electroplating bond and metal wax can be
used.
[0133] Super-abrasive grinding wheel 10 (see FIG. 3) can be
produced as follows: a plurality of super-abrasive grains 1 each
having body 2 having a surface at least partially coated with
coating film 3 (see FIG. 1) are prepared and fixed to outer
peripheral surface 111 of substrate 11 by using bonding material 13
(see FIG. 5). Alternatively, super-abrasive grinding wheel 10 may
be produced as follows: a plurality of bodies 2 for abrasive grains
uncoated with coating film 3 are prepared and fixed to outer
peripheral surface 111 of substrate 11 by using bonding material
13, and thereafter, bodies 2 have their surfaces (or cutting edge
portion) coated with coating film 3. In that case, the coating can
be done in any of the AIP method, HIPIMS method, and arc plasma
powder method mentioned above.
[0134] [Application]
[0135] Super-abrasive grinding wheel 10 according to an embodiment
is suitably applicable to grinding automobile parts, optical glass,
magnetic materials, semiconductor materials, and the like, grinding
to form grooves for end mills, drills and reamers and the like,
grinding to form a breaker for an indexable insert, and heavy duty
grinding for various tools.
[0136] [Function and Effect]
[0137] Super-abrasive grinding wheel 10 according to an embodiment
includes super-abrasive grain 1 with body 2 not easily damaged, and
thus has a high grinding ratio.
Test Example 1
[0138] Difference in grinding performance due to different crystal
grain sizes of coating films of super-abrasive grains was
evaluated.
[0139] [Sample Nos. 1-1 to 1-9]
[0140] Sample Nos. 1-1 to 1-9 each provided a super-abrasive grain
composed of a body and a coating film coating the body's entire
surface. In the present example, the coating film had an external
side without any insulating film formed thereon. This
super-abrasive grain was produced by coating its body's surface
with the coating film. As the body of the abrasive grain,
single-crystal cubic boron nitride having an average grain size of
70 .mu.m was used. The coating film was applied in the arc plasma
powder method. The coating was done with a coating apparatus under
conditions, as follows:
[0141] Coating apparatus: nanoparticle formation apparatus APD-P
produced by ADVANCE RIKO, Inc.
[0142] Target: 50 atomic % of Ti and 50 atomic % of Al
[0143] Introduced gas: N.sub.2
[0144] Deposition pressure: 0.88 Pa
[0145] Discharge voltage: 150 V
[0146] Discharge frequency: 6 Hz
[0147] Capacitor's capacitance: 1080 g
[0148] Shot count: 800,000
[0149] Amount of powder processed: 30 g
[0150] Speed of rotation of powder container: 50 rpm
[0151] Each coating film's composition (atomic %), average crystal
grain size (nm), and average thickness (nm) are shown in Table 1.
Each coating film was applied through a variety of types of devices
and subsequently a typical vacuum heat treatment furnace
(NRF-658-0.7D1.5 V type produced by Nihon-tokusyukikai, with
1.times.10.sup.-3 Pa or less applied) was used to subject it to a
heat treatment varied in temperature as shown in table 1 to provide
a different average crystal grain size. Each coating film was
subjected to a compositional analysis by EDS analysis.
[0152] Each coating film's average crystal grain size was
determined from an HAADF-STEM image obtained through an STEM
(JEM-ARM200F Dual-X produced by JEOL Ltd.). In observing the
HAADF-STEM image of each coating film, the coating film was
mechanically polished and subjected to Ar-ion milling (Dual Mill
600 produced by GATAN) to have a thickness of 100 nm or less. Then,
an acceleration voltage of 200 kV was applied and a magnification
of 6.5 million times was set to observe the HAADF-STEM image of the
coating film in 10 areas in which an atomic arrangement was
observable. One area in which the atomic arrangement was observable
was regarded as one crystal grain, and such 10 crystal grains'
average crystal grain size was regarded as the coating film's
average crystal grain size. The equivalent circle diameter of one
area in which the atomic arrangement was observable was regarded as
one crystal grain size.
[0153] Each coating film's average thickness was determined by
"{(equivalent circle diameter of super-abrasive grain)-(equivalent
circle diameter of body of abrasive grain)}/2." The equivalent
circle diameter of the super-abrasive grain and that of the body
thereof were each an average of equivalent circle diameters
obtained from 30 or more super-abrasive grains in cross section.
The cross section of each super-abrasive grain was exposed as
follows: A molded body in which super-abrasive grains were buried
in epoxy resin was produced. The content of the super-abrasive
grains in the molded body was set to 50% by volume or more with
respect to the resin. The shape of the molded body was a
rectangular parallelepiped or a cube. The molded body was subjected
to a CP (cross section polisher) process. This process was
performed in two stages. In a first stage of the process, the
molded body had any surface processed until a cross section of at
least one super-abrasive grain was visible. Once the cross section
of the super-abrasive grain had been confirmed, then, as a second
stage of the process, the surface was further processed by 50% of
the average grain size of super-abrasive grains. The average grain
size of super-abrasive grains was set to a value as measured with a
laser diffraction type particle size distribution analyzer. The
cross section of the molded body was observed, and an equivalent
circle diameter of each super-abrasive grain and that of the body
of the abrasive grain are determined. The super-abrasive grains'
bodies and coating films and the resin portion underwent an image
analyzing binarization process and thus separated to obtain an
image, from which the super-abrasive grains' cross sections and
their bodies' cross sections were derived and the super-abrasive
grains' equivalent circular diameters and their bodies' equivalent
circular diameters were determined and averaged.
[0154] The super-abrasive grains were used to produce a
super-abrasive grinding wheel similar to super-abrasive grinding
wheel 10 described with reference to FIGS. 3 to 5, comprising a
disk-shaped substrate and a super-abrasive grain layer covering at
least an outer peripheral surface of the substrate. The
super-abrasive grinding wheel was produced using each sample by
fixing a plurality of super-abrasive grains to the outer peripheral
surface of the substrate with a bonding material. Herein, the
substrate was made of S45C, and had a diameter (an outer diameter):
50 mm, a mounting hole diameter (an inner diameter): 20 mm, and a
thickness: 8 mm. The bonding material was an Ag wax material.
[0155] [Evaluation of Grinding Performance]
[0156] The super-abrasive grinding wheel of each sample had its
grinding performance evaluated by determining its grinding ratio.
The grinding ratio was determined as follows: the super-abrasive
grinding wheel of each sample was set in the following apparatus
and ground a workpiece for 180 minutes under the following
conditions, and the grinding ratio was determined from "the volume
of the workpiece ground away/the total worn volume of
super-abrasive grains." That is, the higher the grinding ratio, the
better the grinding performance. The obtained grinding ratios are
shown in Table 1.
[0157] Workpiece: SCM 415 hardened steel (3.5 mm.times.60
mm.times.100 mm)
[0158] Apparatus: Machining Center V-55 produced by Makino
[0159] Grinding wheel's peripheral speed: 2700 mm/min
[0160] Cutting: 1.2 mm
[0161] Feed rate: 50 mm/min
[0162] Coolant: Emulsion type (YUSHIROKEN.RTM.)
[Sample No. 101]
[0163] Sample No. 101 was prepared to be similar to sample No. 1-1
except that the super-abrasive grain was composed of a body alone,
that is, it did not include the coating film, and the samples were
evaluated in grinding performance. A result thereof is shown in
Table 1.
[0164] [Sample Nos. 1-11 to 1-19 and 102]
[0165] As shown in table 2, Sample Nos. 1-11 to 1-19 and 102 were
prepared to be similar to Sample Nos. 1-1 to 1-9 and 101, except
that the super-abrasive grain had a body having a polycrystalline
structure (with an average crystal grain size of 1000 nm), and the
samples were evaluated in grinding performance. A result thereof is
shown in table 2.
[0166] [Sample Nos. 1-21 to 1-29 and 103]
[0167] As shown in table 3, Sample Nos. 1-21 to 1-29 and 103 were
prepared to be similar to Sample Nos. 1-1 to 1-9 and 101, except
that the super-abrasive grain had a body of single-crystal diamond
and that the workpiece was commercially available Inconel.RTM. 718,
and the samples were evaluated in grinding performance. A result
thereof is shown in Table 3.
[0168] [Sample Nos. 1-31 to 1-39 and 104]
[0169] As shown in table 4, Sample Nos. 1-31 to 1-39 and 104 were
prepared to be similar to Sample Nos. 1-1 to 1-9 and 101, except
that the super-abrasive grain had a body of diamond of polycrystal
(with an average crystal grain size of 1000 nm) and that the
workpiece was commercially available Inconel.RTM. 718, and the
samples were evaluated in grinding performance. A result thereof is
shown in table 4.
TABLE-US-00001 TABLE 1 coating coating film condition average heat
crystal treatment grain average sample temperature composition
(atomic %) size thickness grinding nos. (.degree. C.) Ti V Cr Zr Nb
Mo Hf Ta W Al Si C N O (nm) (nm) ratio 1-1 1200 25 -- -- -- -- --
-- -- -- 25 -- -- 50 -- 400 400 1401 1-2 1150 25 -- -- -- -- -- --
-- -- 25 -- -- 50 -- 100 400 1430 1-3 1100 25 -- -- -- -- -- -- --
-- 25 -- -- 50 -- 60 400 1494 1-4 1000 25 -- -- -- -- -- -- -- --
25 -- -- 50 -- 40 400 1502 1-5 900 25 -- -- -- -- -- -- -- -- 25 --
-- 50 -- 20 400 1533 1-6 800 25 -- -- -- -- -- -- -- -- 25 -- -- 50
-- 7 400 1635 1-7 600 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 3
400 1650 1-8 300 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 1 400
1750 1-9 1250 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 600 400
1200 101 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
1100
TABLE-US-00002 TABLE 2 coating coating film condition average heat
crystal treatment grain average sample temperature composition
(atomic %) size thickness grinding nos. (.degree. C.) Ti V Cr Zr Nb
Mo Hf Ta W Al Si C N O (nm) (nm) ratio 1-11 1200 25 -- -- -- -- --
-- -- -- 25 -- -- 50 -- 400 400 1611 1-12 1150 25 -- -- -- -- -- --
-- -- 25 -- -- 50 -- 100 400 1645 1-13 1100 25 -- -- -- -- -- -- --
-- 25 -- -- 50 -- 60 400 1718 1-14 1000 25 -- -- -- -- -- -- -- --
25 -- -- 50 -- 40 400 1727 1-15 900 25 -- -- -- -- -- -- -- -- 25
-- -- 50 -- 20 400 1763 1-16 800 25 -- -- -- -- -- -- -- -- 25 --
-- 50 -- 7 400 1880 1-17 600 25 -- -- -- -- -- -- -- -- 25 -- -- 50
-- 3 400 1898 1-18 300 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 1
400 2013 1-19 1250 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 600
400 1380 102 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
1265
TABLE-US-00003 TABLE 3 coating coating film condition average heat
crystal treatment grain average sample temperature composition
(atomic %) size thickness grinding nos. (.degree. C.) Ti V Cr Zr Nb
Mo Hf Ta W Al Si C N O (nm) (nm) ratio 1-21 1200 25 -- -- -- -- --
-- -- -- 25 -- -- 50 -- 400 400 1155 1-22 1150 25 -- -- -- -- -- --
-- -- 25 -- -- 50 -- 100 400 1179 1-23 1100 25 -- -- -- -- -- -- --
-- 25 -- -- 50 -- 60 400 1232 1-24 1000 25 -- -- -- -- -- -- -- --
25 -- -- 50 -- 40 400 1238 1-25 900 25 -- -- -- -- -- -- -- -- 25
-- -- 50 -- 20 400 1264 1-26 800 25 -- -- -- -- -- -- -- -- 25 --
-- 50 -- 7 400 1348 1-27 600 25 -- -- -- -- -- -- -- -- 25 -- -- 50
-- 3 400 1360 1-28 300 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 1
400 1443 1-29 1250 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 600
400 989 103 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
770
TABLE-US-00004 TABLE 4 coating coating film condition average heat
crystal treatment grain average sample temperature composition
(atomic %) size thickness grinding nos. (.degree. C.) Ti V Cr Zr Nb
Mo Hf Ta W Al Si C N O (nm) (nm) ratio 1-31 1200 25 -- -- -- -- --
-- -- -- 25 -- -- 50 -- 400 400 1160 1-32 1150 25 -- -- -- -- -- --
-- -- 25 -- -- 50 -- 100 400 1184 1-33 1100 25 -- -- -- -- -- -- --
-- 25 -- -- 50 -- 60 400 1237 1-34 1000 25 -- -- -- -- -- -- -- --
25 -- -- 50 -- 40 400 1243 1-35 900 25 -- -- -- -- -- -- -- -- 25
-- -- 50 -- 20 400 1269 1-36 800 25 -- -- -- -- -- -- -- -- 25 --
-- 50 -- 7 400 1353 1-37 600 25 -- -- -- -- -- -- -- -- 25 -- -- 50
-- 3 400 1365 1-38 300 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 1
400 1448 1-39 1250 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 600
400 994 104 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
775
[0170] As shown in Table 1, Sample Nos. 1-1 to 1-9 including a
coating film coating the surface of the body of the abrasive grain
all presented a grinding ratio of 1200 or more, and it can be seen
that the grinding ratio is higher than that of sample No. 101 that
does not include the coating film. Furthermore, Sample Nos. 1-1 to
1-8 having a coating film with a crystal grain size of 400 nm or
less all presented a grinding ratio of 1400 or more, Sample Nos.
1-2 to 1-8 having a coating film with a crystal grain size of 200
nm or less presented a grinding ratio of 1430 or more, Sample Nos.
1-4 to 1-8 having a coating film with a crystal grain size of 50 nm
or less presented a grinding ratio of 1500 or more, Sample Nos. 1-6
to 1-8 having a coating film with a crystal grain size of 10 nm or
less presented a grinding ratio of 1600 or more, and Sample No. 1-8
having a coating film with a crystal grain size of 1 nm presented a
grinding ratio of 1700 or more. That is, it can be seen that the
smaller a coating film is in crystal grain size, the higher a
grinding ratio is.
[0171] As shown in Table 2, even when polycrystalline cubic boron
nitride was used for the body of the abrasive grain, Sample Nos.
1-11 to 1-19 including the coating film all presented a grinding
ratio of 1300 or more, and it can be seen that it is higher than
that of sample No. 102 that does not include the coating film. As
shown in Table 3, even when single-crystal diamond was used for the
body of the abrasive grain, Sample Nos. 1-21 to 1-29 including the
coating film all presented a grinding ratio of 950 or more, and it
can be seen that it is higher than that of sample No. 103 that does
not include the coating film. As shown in Table 4, even when
polycrystalline diamond was used for the body of the abrasive
grain, Sample Nos. 1-31 to 1-39 including the coating film all
presented a grinding ratio of 990 or more, and it can be seen that
it is higher than that of sample No. 104 that does not include the
coating film. As shown in Tables 2 to 4, it can be seen that each
sample having a coating film with a crystal grain size of 400 nm or
less presents a high grinding ratio, and furthermore, samples
having coating films with crystal grain sizes of 200 nm or less, 50
nm or less, particularly 10 nm or less, 1 nm present high grinding
ratios. That is, it can be seen that, as well as Sample Nos. 1-1 to
1-9, Sample Nos. 1-11 to 1-19, 1-21 to 1-29, and 1-31 to 1-39
present higher grinding ratios for smaller crystal grain sizes of
the coating film.
Test Example 2
[0172] Difference in grinding performance due to different
compositions of coating films of super-abrasive grains was
evaluated.
[0173] [Sample No. 2 type samples, sample No. 3 type samples,
sample No. 4 type samples, sample No. 5 type samples, sample No. 6
type samples]
[0174] As shown in Tables 5-9, Sample No. 2 type samples to Sample
No. 6 type samples had their super-abrasive grains with their
coating films made different in composition and were evaluated in
grinding performance, similarly as done for Sample No. 1-1. The
coating films were made different in composition by variously
changing the type of the target in the coating apparatus and the
atmosphere in the apparatus. A shot count of 200,000 was set.
Resultant grinding ratios of Sample No. 2 type samples to Sample
No. 6 type samples are shown in Tables 5-9, respectively.
TABLE-US-00005 TABLE 5 coating film average crystal grain average
sample composition (atomic %) size thickness grinding nos. Ti V Cr
Zr Nb Mo Hf Ta W Al Si C N O (nm) (nm) ratio 2-1 25 25 -- -- -- --
-- -- -- -- -- -- 50 -- 3 100 1540 2-2 25 -- 25 -- -- -- -- -- --
-- -- -- 50 -- 3 100 1565 2-3 25 -- -- 25 -- -- -- -- -- -- -- --
50 -- 3 100 1570 2-4 25 -- -- -- 25 -- -- -- -- -- -- -- 50 -- 3
100 1550 2-5 25 -- -- -- -- 25 -- -- -- -- -- -- 50 -- 3 100 1545
2-6 25 -- -- -- -- -- 25 -- -- -- -- -- 50 -- 3 100 1530 2-7 25 --
-- -- -- -- -- 25 -- -- -- -- 50 -- 3 100 1555 2-8 25 -- -- -- --
-- -- -- 25 -- -- -- 50 -- 3 100 1525 2-9 25 -- -- -- -- -- -- --
-- 25 -- -- 50 -- 3 100 1650 2-10 25 -- -- -- -- -- -- -- -- -- 25
-- 50 -- 3 100 1600
TABLE-US-00006 TABLE 6 coating film average crystal grain average
sample composition (atomic %) size thickness grinding nos. Ti V Cr
Zr Nb Mo Hf Ta W Al Si C N O (nm) (nm) ratio 3-1 25 25 -- -- -- --
-- -- -- -- -- 25 25 -- 3 100 1542 3-2 25 -- 25 -- -- -- -- -- --
-- -- 25 25 -- 3 100 1569 3-3 25 -- -- 25 -- -- -- -- -- -- -- 25
25 -- 3 100 1572 3-4 25 -- -- -- 25 -- -- -- -- -- -- 25 25 -- 3
100 1552 3-5 25 -- -- -- -- 25 -- -- -- -- -- 25 25 -- 3 100 1547
3-6 25 -- -- -- -- -- 25 -- -- -- -- 25 25 -- 3 100 1532 3-7 25 --
-- -- -- -- -- 25 -- -- -- 25 25 -- 3 100 1557 3-8 25 -- -- -- --
-- -- -- 25 -- -- 25 25 -- 3 100 1527 3-9 25 -- -- -- -- -- -- --
-- 25 -- 25 25 -- 3 100 1640 3-10 25 -- -- -- -- -- -- -- -- -- 25
25 25 -- 3 100 1602 3-11 33 -- -- -- -- -- -- -- -- -- -- 33 33 --
3 100 1550 3-12 17 -- -- -- -- -- -- -- -- 16 17 25 25 -- 3 100
1530 3-13 -- -- -- -- -- -- -- -- -- 25 25 25 25 -- 3 100 1450
TABLE-US-00007 TABLE 7 coating film average crystal grain average
sample composition (atomic %) size thickness grinding nos. Ti V Cr
Zr Nb Mo Hf Ta W Al Si C N O (nm) (nm) ratio 4-1 25 25 -- -- -- --
-- -- -- -- -- 50 -- -- 3 100 1543 4-2 25 -- 25 -- -- -- -- -- --
-- -- 50 -- -- 3 100 1568 4-3 25 -- -- 25 -- -- -- -- -- -- -- 50
-- -- 3 100 1573 4-4 25 -- -- -- 25 -- -- -- -- -- -- 50 -- -- 3
100 1553 4-5 25 -- -- -- -- 25 -- -- -- -- -- 50 -- -- 3 100 1548
4-6 25 -- -- -- -- -- 25 -- -- -- -- 50 -- -- 3 100 1533 4-7 25 --
-- -- -- -- -- 25 -- -- -- 50 -- -- 3 100 1558 4-8 25 -- -- -- --
-- -- -- 25 -- -- 50 -- -- 3 100 1528 4-9 25 -- -- -- -- -- -- --
-- 25 -- 50 -- -- 3 100 1638 4-10 25 -- -- -- -- -- -- -- -- -- 25
50 -- -- 3 100 1603
TABLE-US-00008 TABLE 8 coating film average crystal average sample
composition (atomic %) grain size thickness grinding nos. Ti V Cr
Zr Y Mg Ca Nb Mo Hf Ta W Al Si C N O (nm) (nm) ratio 5-1 33 -- --
-- -- -- -- -- -- -- -- -- -- -- -- -- 67 3 100 1350 5-2 -- -- 40
-- -- -- -- -- -- -- -- -- -- -- -- -- 60 3 100 1430 5-3 -- -- --
33 -- -- -- -- -- -- -- -- -- -- -- -- 67 3 100 1500 5-4 -- -- --
-- -- -- -- -- -- 33 -- -- -- -- -- -- 67 3 100 1330 5-5 -- -- --
-- -- -- -- -- -- -- 29 -- -- -- -- -- 71 3 100 1360 5-6 -- -- --
-- -- -- -- -- -- -- -- 25 -- -- -- -- 75 3 100 1320 5-7 -- -- --
-- -- -- -- -- -- -- -- -- 40 -- -- -- 60 3 100 1510 5-8 -- -- --
-- -- -- -- -- -- -- -- -- -- 33 -- -- 67 3 100 1340 5-9 -- -- --
-- 40 -- -- -- -- -- -- -- -- -- -- -- 60 3 100 1340 5-10 -- -- --
-- -- 50 -- -- -- -- -- -- -- -- -- -- 50 3 100 1350 5-11 -- -- --
-- -- -- 50 -- -- -- -- -- -- -- -- -- 50 3 100 1330
TABLE-US-00009 TABLE 9 coating film average crystal grain average
sample composition (atomic %) size thickness grinding nos. Ti V Cr
Zr Nb Mo Hf Ta W Al Si C N O (nm) (nm) ratio 6-1 22.5 -- -- 5 -- --
-- -- -- 22.5 -- -- 50 -- 3 100 1595 6-2 22.5 -- -- -- 5 -- -- --
-- 22.5 -- -- 50 -- 3 100 1580 6-3 22.5 -- -- -- -- -- -- 5 -- 22.5
-- -- 50 -- 3 100 1590 6-4 22.5 -- -- -- -- -- -- -- -- 22.5 5 --
50 -- 3 100 1620 6-5 -- -- 15 -- -- -- -- -- -- 35 -- -- 50 -- 3
100 1610 6-6 -- -- 25 -- -- -- -- -- -- 25 -- -- 50 -- 3 100 1600
6-7 -- -- -- -- -- -- -- -- -- -- -- 100 -- -- 3 100 1400 (DLC) 6-8
-- -- -- -- -- -- -- -- -- -- -- 100 -- -- 3 100 1500 (diamond)
[0175] As shown in Tables 5 to 9, whichever composition the coating
film may have, sample No. 2 type samples to sample No. 6 type
samples having a coating film with a small average crystal grain
diameter all presented a grinding ratio of 1200 or more, and
furthermore, 1300 or more, and it can be seen that it is higher
than that of sample No. 101 of test example 1. Inter alia, all of
Sample No. 2 type samples, sample Nos. 3-1 to 3-12, all of Sample
No. 4 type samples, sample Nos. 5-3, 5-8, 6-1 to 6-6 and 6-8 all
presented a grinding ratio of 1500 or more, and it can be seen that
it is significantly high.
Test Example 3
[0176] Difference in grinding performance due to difference in
thickness of coating films of super-abrasive grains was
evaluated.
[0177] [Sample Nos. 7-1 to 7-7]
[0178] Sample Nos. 7-1 to 7-7 were prepared to be similar to Sample
No. 1-7 except that the former had their super-abrasive grains with
their coating films made different in thickness, as shown in Table
10, and the samples were evaluated in grinding performance. The
coating films were made different in thickness by adjusting a
processing time. The longer the processing time is, the thicker the
coating film is. A result of grinding ratios of sample Nos. 7-1 to
7-7 is shown in table 10.
TABLE-US-00010 TABLE 10 coating film average crystal grain average
sample composition (atomic %) size thickness grinding nos. Ti V Cr
Zr Nb Mo Hf Ta W Al Si C N O (nm) (nm) ratio 7-1 25 -- -- -- -- --
-- -- -- 25 -- -- 50 -- 3 0.5 1150 7-2 25 -- -- -- -- -- -- -- --
25 -- -- 50 -- 3 1 1530 7-3 25 -- -- -- -- -- -- -- -- 25 -- -- 50
-- 3 10 1550 7-4 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 3 100
1700 7-5 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 3 1000 1832 7-6
25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 3 5000 1500 7-7 25 -- --
-- -- -- -- -- -- 25 -- -- 50 -- 3 8000 1230
[0179] As shown in Table 10, sample Nos. 7-2 to 7-7 having a
coating film with a small average crystal grain size and an average
thickness of 1 nm or more all presented a grinding ratio of 1200 or
more, and it can be seen that it is higher than that of Sample No.
7-1 having a coating film with an average thickness of less than 1
nm and that of sample No. 101 in test example 1 having a coating
film with a large average crystal grain size. Inter alia, it can be
seen that sample Nos. 7-2 to 7-6 having a coating film with an
average thickness of 1 nm or more and 5000 nm or less present a
grinding ratio higher than that of Sample No. 7-7 having a coating
film with an average thickness exceeding 5000 nm.
Test Example 4
[0180] Difference in grinding performance due to different
structures of coating films of super-abrasive grains was
evaluated.
[0181] [Sample Nos. 8-1 and 8-2]
[0182] Sample Nos. 8-1 and 8-2 were prepared to be similar to those
in test example 1 except that the former had their super-abrasive
grains with their coating films having a multilayer structure
composed of a plurality of stacked ceramic layers, as shown in
Table 11, and the samples were evaluated in grinding performance.
Sample No. 8-1 had a coating film in a two-layer structure, and
Sample No. 8-2 had a coating film in a three-layer structure.
Sample No. 8-1 had a first layer on the side of the body of the
abrasive grain and a second layer outer than the first layer, and
the first and second layers are composed of different materials.
When Sample No. 8-2 has first to third layers sequentially as seen
on the side of the body of the abrasive grain outward, the first
and third layers are formed of identical materials and the first
layer (and the third layer) and the second layer are formed of
different materials. The layers are equal in average crystal grain
size and average thickness. The coating film having the two-layer
structure was formed by performing a coating process twice and the
coating film having the three-layer structure was formed by
performing the coating process three times.
TABLE-US-00011 TABLE 11 coating film average crystal grain average
sample composition (atomic %) size thickness grinding nos. Ti V Cr
Zr Nb Mo Hf Ta W Al Si C N O (nm) (nm) ratio 8-1 1st 25 -- -- -- --
-- -- -- -- 25 -- -- 50 -- 3 50 1700 layer 2nd -- -- 25 -- -- -- --
-- -- 25 -- -- 50 -- 3 50 layer 8-2 1st 25 -- -- -- -- -- -- -- --
25 -- -- 50 -- 3 33.33 1740 layer 2nd -- -- 25 -- -- -- -- -- -- 25
-- -- 50 -- 3 33.33 layer 3rd 25 -- -- -- -- -- -- -- -- 25 -- --
50 -- 3 33.33 layer
[0183] As shown in Table 11, Sample Nos. 8-1 and 8-2 have a
grinding ratio of 1700 or more, and it can be seen that when a case
with a coating film of a monolayer structure is compared with that
with a coating film having a larger number of layers, the latter
tends to present a higher grinding ratio.
Test Example 5
[0184] After a super-abrasive grinding wheel was produced it was
coated with a coating film, and the thus coated wheel was evaluated
for difference in grinding performance due to different crystal
grain sizes of the coating film.
[0185] [Sample No. 9-1]
[0186] Sample No. 9-1 is different in how a super-abrasive grinding
wheel is produced. This super-abrasive grinding wheel was produced
as follows: a plurality of bodies for abrasive grains that were not
coated with a coating film were prepared, and a bonding material
was used to fix the bodies for abrasive grains to the outer
peripheral surface of the disk-shaped substrate and subsequently
the coating film was formed to coat a cutting edge portion of the
bodies for abrasive grains. The coating film was applied in the arc
plasma powder method. The coating was done with a coating apparatus
under conditions, as indicated below. Using this super-abrasive
grinding wheel, grinding performance was evaluated in the same
manner as in Test Example 1. A result thereof is shown in table
12.
[0187] Coating apparatus: nanoparticle formation apparatus APD-P
produced by ADVANCE RIKO, Inc.
[0188] Target: 50 atomic % of Ti and 50 atomic % of Al
[0189] Introduced gas: N.sub.2
[0190] Deposition pressure: 0.88 Pa
[0191] Discharge voltage: 150 V
[0192] Discharge frequency: 6 Hz
[0193] Capacitor's capacitance: 1080 g
[0194] Shot count: 1,000
[0195] Speed of rotation of powder container: 50 rpm
TABLE-US-00012 TABLE 12 coating film average crystal grain average
sample composition (atomic %) size thickness grinding no. Ti V Cr
Zr Nb Mo Hf Ta W Al Si C N O (nm) (nm) ratio 9-1 25 -- -- -- -- --
-- -- -- 25 -- -- 50 -- 3 400 1620
[0196] As shown in Table 12, Sample No. 9-1 presents a grinding
ratio of 1600 or more and is found to be very high. Thus it can be
seen that the grinding ratio can be improved by coating the surface
of the body of the abrasive grain with the coating film.
[0197] It is believed that even if the coating film does not coat
the surface of the body of the abrasive grain entirely, the coating
film has an effect in improving the grinding ratio insofar as the
coating film coats the surface at least partially. For example,
even if truing a super-abrasive grinding wheel to have a surface
uniform in level or the like results in an abrasive grain having a
body with a cutting edge portion having a surface locally uncoated
with the coating film, it is believed to be effective in improving
the grinding ratio insofar as the cutting edge portion has the
surface with a 50% or more thereof in area coated with the coating
film.
Test Example 6
[0198] Difference in grinding performance depending on
presence/absence of the insulating film on the outer surface of the
coating film of the super-abrasive grain was evaluated.
[0199] [Sample Nos. 10-1 to 10-8]
[0200] Sample Nos. 10-1 to 10-8 provided super-abrasive grains each
composed of a body, a coating film coating the entire surface area
of the body, and an insulating film covering the entire surface
area of the coating film. The insulating film was formed under the
same conditions using the coating apparatus of Test Example 1.
Sample Nos. 10-1 to 10-8 had the same body and coating film as
those of Sample No. 2-9. Sample Nos. 10-1 to 10-3 had insulating
films made different in composition, as shown in table 13. The
different compositions were provided by variously changing the type
of the target in the coating apparatus and the atmosphere in the
apparatus. Sample Nos. 10-4 to 10-8 had their insulating films
identical in composition to that of Sample No. 10-1 and made
different in average thickness. Difference in average thickness was
provided by adjusting a processing time. The longer the processing
time is, the thicker the insulating film is.
[0201] Using this super-abrasive grain, a super-abrasive grinding
wheel was produced in the same manner as in Test Example 1 except
for the type of the bonding material. In this example, the bonding
material is composed of a nickel plating layer. Initially, an area
of the substrate excluding the outer peripheral surface is masked
to expose the outer peripheral surface through the masking. A
nickel plating layer is precipitated on the exposed outer
peripheral surface of the substrate by electroplating to
temporarily attach super-abrasive grains. Then, on a surface of the
nickel plating layer, a nickel plating layer was applied thickly by
electroless plating to fix super-abrasive grains to the outer
peripheral surface of the substrate.
[0202] Using this super-abrasive grinding wheel, grinding
performance was evaluated, similarly as done in test example 1. A
result thereof is shown in Table 13.
[0203] [Sample Nos. 105 and 106]
[0204] Sample No. 105 provided a super-abrasive grain identical to
that of sample No. 2-9, that is, excluding the insulating film and
composed of the body for the abrasive grain and the coating film.
Sample No. 106 provided a super-abrasive grain identical to that of
sample No. 101, that is, excluding the coating film and the
insulating film and composed only of the body for the abrasive
grain. As well as Sample No. 10-1 or the like, Sample Nos. 105 and
106 had super-abrasive grains fixed to the outer peripheral surface
of the substrate by a nickel plating layer through electroplating
and electroless plating.
TABLE-US-00013 TABLE 13 coating film insulating film average
average average grain thick- thick- sample composition (atomic %)
size ness composition (atomic %) ness grinding nos. Ti V Cr Zr Nb
Mo Hf Ta W Al Si C N O (nm) (nm) Al Zr Si N O (nm) ratio 10-1 25 --
-- -- -- -- -- -- -- 25 -- -- 50 -- 3 100 40 -- -- -- 60 100 1600
10-2 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 3 100 -- 33 -- -- 67
100 1588 10-3 25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 3 100 21.4
21.4 35.8 21.4 100 1595 10-4 25 -- -- -- -- -- -- -- -- 25 -- -- 50
-- 3 100 40 -- -- -- 60 0.5 * 10-5 25 -- -- -- -- -- -- -- -- 25 --
-- 50 -- 3 100 40 -- -- -- 60 1 * 10-6 25 -- -- -- -- -- -- -- --
25 -- -- 50 -- 3 100 40 -- -- -- 60 500 1630 10-7 25 -- -- -- -- --
-- -- -- 25 -- -- 50 -- 3 100 40 -- -- -- 60 5000 1420 10-8 25 --
-- -- -- -- -- -- -- 25 -- -- 50 -- 3 100 40 -- -- -- 60 6000 * 105
25 -- -- -- -- -- -- -- -- 25 -- -- 50 -- 3 100 -- -- -- -- -- -- *
106 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
-- 1100
[0205] As shown in Table 13, it can be seen that Sample Nos. 10-1
to 10-3, 10-6, and 10-7 having an insulating film with an average
thickness of more than 1 nm and 5000 nm or less present a high
grinding ratio.
[0206] In contrast, Sample Nos. 10-4, 10-5, 10-8, and 105 caused a
defect inviting impaired grinding performance. The ground therefor
is as follows: Sample No. 10-4 had an insulating film with an
average thickness of less than 1 nm and was unable to increase
insulation, allowing a plating film to grow on a surface of the
insulating film. Sample No. 10-5 had an insulating film with an
average thickness of 1 nm, and a portion having low insulating
performance was locally formed and a plating film locally grew on a
surface of the insulating film. Sample No. 10-8 had an insulating
film with an average thickness of 6000 nm and thus excessively
large in thickness so that it was unable to maintain a state of
covering the outer surface of the coating film. As a result, a
plating film grew, similarly as seen in Sample No. 10-4. Sample No.
105 had no insulating film and in addition, had an electrically
conductive coating film, and accordingly, a plating film grew on a
surface of the coating film.
[0207] Although Sample No. 106 neither had a coating film nor an
insulating film and had no plating film growing on a surface of the
body of the abrasive grain, the sample presented a low grinding
ratio due to the absence of the coating film.
[0208] Note that the present invention is not limited to these
examples, and is intended to include any modifications within the
meaning and scope indicated by and equivalent to the terms of the
claims.
REFERENCE SIGNS LIST
[0209] 1 super-abrasive grain, 2 body of abrasive grain, 3 coating
film, 31 first layer, 32 second layer, 33 third layer, 4 insulating
film, 10 super-abrasive grinding wheel, 11 substrate, 111 outer
peripheral surface, 12 super-abrasive grain layer, 13 bonding
material.
* * * * *