U.S. patent application number 12/077835 was filed with the patent office on 2008-09-25 for substrate treatment method for portion to be coated.
This patent application is currently assigned to FUJI MANUFACTURING CO., LTD.. Invention is credited to Shozo Ishibashi, Keiji Mase.
Application Number | 20080233838 12/077835 |
Document ID | / |
Family ID | 39736392 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080233838 |
Kind Code |
A1 |
Mase; Keiji ; et
al. |
September 25, 2008 |
Substrate treatment method for portion to be coated
Abstract
A portion to be coated of a workpiece is subjected to substrate
treatment by blasting to provide an anchor effect without leaving
abrasive grains thereon. A substrate treatment method for a portion
to be coated includes ejecting an elastic abrasive onto a portion
to be coated of a workpiece to form irregularities with a
predetermined surface roughness, thereby providing an anchor effect
for a coating to be formed without causing the abrasive grains to
be embedded in the surface of the workpiece. The elastic abrasive
includes elastic carriers and abrasive grains, particularly,
insulating abrasive grains, compounded and dispersed in the base
material as an elastic body or carried on surfaces of the base
materials by, for example, adhesion.
Inventors: |
Mase; Keiji; (Edogawa-ku,
JP) ; Ishibashi; Shozo; (Edogawa-ku, JP) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
FUJI MANUFACTURING CO.,
LTD.
Edogawa-ku
JP
|
Family ID: |
39736392 |
Appl. No.: |
12/077835 |
Filed: |
March 21, 2008 |
Current U.S.
Class: |
451/38 |
Current CPC
Class: |
B24C 1/08 20130101; B24C
1/06 20130101; B24C 11/00 20130101 |
Class at
Publication: |
451/38 |
International
Class: |
B24C 1/04 20060101
B24C001/04; B24C 11/00 20060101 B24C011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2007 |
JP |
2007-76166 |
Claims
1. A substrate treatment method for a portion to be coated, the
method comprising; ejecting an elastic abrasive onto a portion to
be coated of a workpiece to form irregularities with a
predetermined surface roughness, thereby providing an anchor effect
for a coating to be formed on the portion to be coated without
causing the abrasive grains to be embedded in the portion to be
coated, the elastic abrasive including base material as an elastic
body and abrasive grains compounded and dispersed in the base
material as an elastic body or carried on surfaces of the base
material as an elastic body.
2. The substrate treatment method for a portion to be coated
according to claim 1, wherein; the surface roughness of the portion
to be coated is controlled by changing the grain size of the
abrasive grains in the elastic abrasive.
3. The substrate treatment method for a portion to be coated
according to claim 1, wherein; the surface roughness of the portion
to be coated is controlled by changing conditions under which the
elastic abrasive is ejected.
4. The substrate treatment method for a portion to be coated
according to claim 1, wherein; the abrasive grains are insulating
and have an average grain size of 0.5 to 230 .mu.m; the elastic
abrasive has an average grain size of 10 to 2,000 .mu.m, the
average grain size being selected on the basis of that of the
abrasive grains; and the elastic abrasive is ejected at an ejection
pressure of 0.01 to 0.5 MPa, an ejection distance of 10 to 200 mm,
and an incident angle of 30.degree. to 75.degree..
5. The substrate treatment method for a portion to be coated
according to claim 1, wherein; there is no increase in an atom
percent of silicon (Si) in the elastic abrasive.
6. The substrate treatment method for a portion to be coated
according to claim 1, wherein; the coating is formed by a method in
which a voltage is applied to the workpiece excluding hard and
brittle materials, and the abrasive grains are formed of an
insulating material such as carborundum, green carborundum, or
alumina.
7. The substrate treatment method for a portion to be coated
according to claim 4, wherein; the abrasive grains are insulating
and have an average grain size of 1.0 to 40 .mu.m and the abrasive
grains are mixed and dispersed in the elastic abrasive made of
rubber has an average grain size of 35 to 1,000 .mu.m, the average
grain size being selected on the basis of that of the abrasive
grains; and the elastic abrasive is ejected at an ejection pressure
of 0.02 to 0.5 MPa, an ejection distance of 50 to 100 mm.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to substrate treatment methods
for a portion on which a coating is to be formed (referred to as a
"portion to be coated" in the present invention) of an article to
be treated, namely, a workpiece, and particularly to a substrate
treatment method for a portion to be coated of a workpiece, such as
a sliding part, by blasting before a coating is formed on the
surface of the sliding part for various purposes, including
increased hardness, reduced friction, improved corrosion
resistance, improved high-temperature oxidation resistance, and
decoration.
[0003] 2. Description of the Prior Art
[0004] The term "blasting" used in the present invention refers to
a wide variety of blasting methods by which an abrasive can be
ejected onto a portion to be coated of a workpiece at a
predetermined ejection speed and pressure. Examples of blasting
methods include fluid blasting, such as dry blasting and wet
blasting, in which the abrasive is ejected with a compressed fluid
such as compressed air, centrifugal blasting (impeller blasting),
in which the abrasive is ejected by applying a centrifugal force
generated by rotating an impeller, and impact blasting, in which
the abrasive is hit and ejected by an impact rotor.
[0005] In general, a coating of diamond-like carbon (DLC), TiAIN,
TiN, or TiC, for example, is formed on a portion over which another
member slides, such as a cutting edge of a cutting tool, for
various purposes, including increased hardness, reduced friction,
improved corrosion resistance, and improved high-temperature
oxidation resistance.
[0006] When the coating is to be formed on the surface of the
workpiece, the portion to be coated is roughened to a predetermined
surface roughness so that the coating adheres firmly to the surface
of the workpiece. This substrate treatment allows some of the
coating to enter irregularities formed in the coated surface to
provide namely "an anchor effect", thus increasing the peeling
strength (strength for scrape to peel off) of the coating and
therefore its durability.
[0007] Examples of methods for roughening the portion to be coated
to a predetermined surface roughness in the substrate treatment
performed before the coating is formed include grinding, chemical
etching, reactive ion etching, laser processing, and blasting.
[0008] Of these, blasting can be relatively easily performed simply
by ejecting abrasive grains onto the portion to be coated. This
method, in particular, has attracted attention because it allows
substrate treatment to be carried out at relatively low cost.
[0009] When the portion to be coated of the workpiece is subjected
to substrate treatment by blasting, the speed of the abrasive
grains upon collision can reach, for example, 200 m/s or more.
[0010] The abrasive grains used are generally formed of a material
harder than the workpiece so that the surface of the workpiece can
be successfully treated, for example, cut. Use of such abrasive
grains has been found to cause a phenomenon whereby, when the
abrasive grains collide with the workpiece at high speed as
described above, they stick into the surface of the workpiece and
are then further embedded on the surface thereof and nearly the
surface therein when succeeding abrasive grains collide with the
stuck grains.
[0011] The embedding of the abrasive grains is particularly
noticeable if the workpiece is formed of a malleable and ductile
material with a relatively low hardness, such as aluminum, copper,
brass, or zinc. In addition to such materials, the above phenomenon
occurs for a variety of materials including metals, cemented
carbide, which is a metal composite, semiconductors such as
silicon, and engineering plastics, but excluding hard and brittle
materials such as glass and ceramics.
[0012] The applicant has proposed a method for forming a glossy
surface such as a mirror-finished surface by sand blasting,
although this method is not intended for substrate treatment of a
portion to be coated (see Japanese Unexamined Patent Application
Publication No. 2005-22015 (Patent Document 1)). According to this
method, abrasive grains are ejected together with a compressed
fluid onto a surface of a workpiece at an incident angle .theta.
such that the following condition is satisfied:
0<Vsin .theta..ltoreq.1/2V
where V is the speed of the abrasive grains in an ejection
direction and .theta. is the angle at which the abrasive grains are
incident on the surface of the workpiece. This method produces a
jet of abrasive grains along the surface of the workpiece.
[0013] As described above, when the substrate treatment for
providing the anchor effect is performed by blasting to improve,
for example, the peeling resistance of the coating, the blasting
causes the abrasive grains to be embedded in the surface of the
workpiece.
[0014] The embedded abrasive grains cause problems in a subsequent
coating process.
[0015] For example, if the subsequent coating process is performed
by vapor deposition such as physical vapor deposition (PVD) or
chemical vapor deposition (CVD), no coating is formed in regions
around protuberances formed by the embedded abrasive grains because
these regions are shaded by the protuberances during film growth.
This results in uneven film thickness and formation of thin
portions.
[0016] Even if a coating with a uniform thickness can be formed on
the surface of the workpiece, including the protuberances formed by
the embedded abrasive grains, the coating will have protuberances
corresponding to those formed on the underlying surface, that is,
the surface of the workpiece.
[0017] Hence, if such a coating is formed on, for example, a
sliding part of a cutting tool, chips collide with the thin
portions or protuberances in the coating, thus damaging the
coating. This impairs the function of the coating because, for
example, the coating starts to be broken and delaminated from the
damaged portions.
[0018] If the coating is formed by a method in which a voltage is
applied to the workpiece, such as PVD or electroplating, and if the
abrasive grains embedded on the surface of or in nearly the surface
of the portion to be coated are formed of an insulating material
such as carborundum, green carborundum, or alumina, difference in
applied voltages is occurred between the sites where the abrasive
grains are embedded and their vicinities. This results in formation
of a coating with uneven thickness or, in some cases, even failure
to form a coating at the sites where the abrasive grains are
embedded. Thus, the embedded abrasive grains can cause various
problems in the coating process.
[0019] According to the blasting method disclosed in Patent
Document 1, the incident angle .theta. at which the abrasive grains
are ejected onto the workpiece is set at a predetermined oblique
angle to reduce a perpendicular force component exerted on the
abrasive grains, thereby preventing the surface of the workpiece
from becoming a satin finished surface. This method allows for a
reduction in the force exerted in such a direction as to embed the
abrasive grains in the surface of the workpiece.
[0020] The results of an experiment carried out by the inventor of
the present invention, however, have revealed that the embedding of
the abrasive grains in the surface of the workpiece cannot be
prevented by setting the incident angle .theta. at which the
abrasive grains are ejected at a predetermined oblique angle, as in
the method described in Patent Document 1. Thus, the above problem
due to the residual abrasive grains cannot be solved simply by
applying the method described in Patent Document 1 to the substrate
treatment of the portion to be coated.
[0021] It is also possible to remove the abrasive grains embedded
in the surface of the workpiece during blasting by polishing the
surface of the workpiece by a method other than blasting, or by
chemically etching the surface of the workpiece, after the blasting
has been completed. For such methods, however, it is difficult to
remove only the outermost portion, having the abrasive grains
embedded therein, while maintaining the surface unevenness formed
in the workpiece by blasting, and it is extremely difficult to
control the surface roughness of the portion to be coated of the
final product so that it can provide the anchor effect.
[0022] In addition, the use of a method other than blasting to
remove the embedded abrasive grains, as described above, inevitably
increases the cost of the substrate treatment because, for example,
it complicates the process and requires an additional processing
apparatus.
[0023] Accordingly, an object of the present invention, which has
been made to solve the above problems of the related art, is to
provide a substrate treatment method for a portion to be coated, so
that it can provide an anchor effect, by a relatively simple
method, namely, blasting, without causing abrasive grains to be
embedded in the portion to be coated despite employing blasting for
the surface processing.
SUMMARY OF THE INVENTION
[0024] To achieve the above object, a substrate treatment method
for a portion to be coated according to the present invention
includes ejecting an elastic abrasive onto a portion to be coated
of a workpiece to form irregularities with a predetermined surface
roughness, thereby providing an anchor effect for a coating to be
formed on the portion to be coated without causing the abrasive
grains to be embedded on the portion to be coated. The elastic
abrasive includes a base material as an elastic body and abrasive
grains compounded and dispersed in the base material as an elastic
body or carried on surfaces of the base material as an elastic
body.
[0025] In the above substrate treatment method for a portion to be
coated, the surface roughness of the portion to be coated may be
controlled by changing the grain size of the abrasive grains. In
addition to or instead of changing the grain size of the abrasive
grains, the surface roughness of the portion to be coated may be
controlled by changing conditions under which the elastic abrasive
is ejected.
[0026] To avoid electrical problems in the case where the abrasive
grains are insulating, preferably, the abrasive grains have an
average grain size of 0.5 to 230 .mu.m, the elastic abrasive has an
average grain size of 10 to 2,000 .mu.m, the average grain size
being selected on the basis of that of the abrasive grains, and the
elastic abrasive is ejected at an ejection pressure of 0.01 to 0.5
MPa, an ejection distance of 10 to 200 mm, and an incident angle of
30.degree. to 75.degree..
[0027] In the present invention, the abrasive may contain a
colorant or a fluorescent colorant, such as an inorganic pigment or
an organic pigment. Examples of the colorant include titanium
oxide, zinc oxide, carbon black, white carbon, silica, mica,
aluminum powder, metal flakes, iron oxide, azo dye, anthraquinone
dye, indigo dye, sulfur dye, and phthalocyanine dye. The abrasive
may also contain a perfume or an antimicrobial agent.
[0028] The abrasive may be ejected by a direct-pressure method, for
example, by direct pressure, gravity, suction, or blowing.
[0029] In electroplating, which is an example of a coating method,
as described above, a metal dissolved in a solution in a plating
bath is electrochemically deposited on the surface of a workpiece
by dipping the workpiece in the bath and supplying electricity
through electrodes; therefore, it cannot be applied to insulating
workpieces. Accordingly, a coating cannot stably be formed on any
portion where an insulator is present on the surface of the
workpiece. Any coating thus formed will exhibit peeling.
[0030] Even if a coating can be formed on a portion where a minute
insulator is present, depending on the conditions of the electric
field applied to the vicinity thereof, the coating may be defective
as an electroplated coating because the insulator swells, thus
impairing the surface adhesion.
[0031] To prevent the abrasive grains of the elastic abrasive,
containing such an insulating material, from being embedded on the
portion to be coated, the following processing conditions are
preferred.
[0032] The processing pressure preferably ranges from 0.01 to 0.5
MPa. A pressure of less than 0.01 MPa is unsuitable for industrial
use because the abrasive will be ejected from a nozzle at low
ejection speed, and accordingly the surface of the workpiece will
be processed at low processing speed (cutting speed). If the media
are ejected at a processing pressure above 0.5 MPa, they collide
with the surface of the workpiece at high processing speed and
therefore experience a high load that forces the abrasive grains to
come off the media, thus decreasing the life of the media. In
addition, the processing speed decreases as more abrasive grains
come off. Furthermore, the abrasive grains that come off are
circulated and ejected from the nozzle again, thus causing the
problem of embedded abrasive grains described above. More
preferably, the processing pressure ranges from 0.02 to 0.4
MPa.
[0033] The ejection distance preferably ranges from 10 to 200 mm.
If the ejection distance falls less than 10 mm, the distance
between the substrate and the ejection nozzle is so small that the
point of ejection on the workpiece at which the media are ejected
is locally processed, thus causing unevenness. If the ejection
distance is above 200 mm, it is difficult to efficiently process a
target processing site because the media are ejected from the
nozzle over an extended area. Preferably, the ejection distance
ranges from 50 to 150 mm.
[0034] A nozzle tip from which the abrasive is ejected may have any
shape that is appropriate for the surface conditions of the
workpiece, such as a circular, rectangular, polygonal, or
elliptical shape. For a circular nozzle tip, the diameter may be
0.5 to 20 mm. If the diameter is less than 0.5 mm, the nozzle has
low processing capability because of low ejection energy due to
loss of kinetic energy inside a flow channel and loss of energy at
a wall surface inside the nozzle.
[0035] The abrasive grains used preferably have an average grain
size of 0.5 to 230 .mu.m. The surface to be processed can be
treated to a lower surface roughness as the average grain size of
the abrasive grains is reduced, under the same ejection conditions,
including the ejection pressure, the ejection distance, the
incident angle, and the average grain size of the elastic abrasive.
In addition, the average grain size of the abrasive grains must be
determined so that they can be carried by the base material as an
elastic body without coming off under the particular ejection
conditions. Smaller abrasive grains have a larger surface area and
adhere more firmly to the base material as an elastic body than
larger abrasive grains. Hence, the minimum grain size should be 0.5
.mu.m (#20,000). The maximum grain size, on the other hand, should
be 230 .mu.m. Any larger grain size results in low adhesion to the
base material as an elastic body. Such abrasive grains can come
off, thus failing to provide a desired surface state, depending on
the ejection conditions. In addition, the abrasive grains that come
off are circulated, ejected from the nozzle, and embedded in the
workpiece. More preferably, the average grain size ranges from 0.5
.mu.m (#20,000) to 140 .mu.m (#90).
[0036] The average grain size of the elastic abrasive depends on
the shape and surface roughness of the workpiece. When controlling
the surface roughness at the bottom of a groove shape, it cannot be
sufficiently processed using an elastic abrasive having an average
grain size larger than the size of the groove. Multiple grains must
be allowed to enter the groove to process its surface. Hence, the
grain size of the abrasive must be one third or less the size of
the groove. The minimum average grain size of the abrasive is
therefore preferably 10 .mu.m.
[0037] In treating the surface of a flat workpiece, an abrasive
with a larger grain size is advantageous in terms of processing
efficiency; the grain size can be up to 2,000 .mu.m. Any larger
grain size results in a lower processing efficiency because it can
be assumed that the number of grains ejected per unit time is
decreased. Preferably, the grain size ranges from 20 to 1,500
.mu.m. The minimum and maximum grain sizes are 5 .mu.m and 20
.mu.m, respectively, for an average grain size of 10 .mu.m, and are
1,800 .mu.m and 2,200 .mu.m, respectively, for an average grain
size of 2,000 .mu.m, as detailed in Table 2 below.
[0038] As described above, the substrate treatment method for a
portion to be coated according to the present invention has the
following significant benefits.
[0039] It is possible to treat the surface of the workpiece to a
desired surface roughness by a relatively simple method, namely,
blasting, while successfully preventing the abrasive grains from
being embedded on the surface of the workpiece.
[0040] As a result, it is possible to improve the adhesion
strength, for example, of the coating to be formed while
successfully preventing problems such as uneven thickness due to
embedding of the abrasive grains and coating defects caused when
the coating is formed by a method involving application of a
voltage, such as PVD or electroplating.
[0041] It is also possible to easily control the surface roughness
of the irregularities formed on the portion to be coated by
changing the grain size of the abrasive grains ejected and/or the
ejection conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] The objects and advantages of the invention will become
apparent from the following detailed description of preferred
embodiments thereof provided in connection with the accompanying
drawings in which:
[0043] FIG. 1 is a diagram illustrating a force exerted on abrasive
grains;
[0044] FIGS. 2A to 2D are electron micrographs of a sample of
Example 1 (formed of SPCC): FIG. 2A is a scanning electron
microscope (SEM) image; FIG. 2B is a carbon (C) energy dispersive
X-ray spectroscope (EDX) image; FIG. 2C is an iron (Fe) EDX image;
and FIG. 2D is a silicon (Si) EDX image;
[0045] FIGS. 3A to 3D are electron micrographs of a sample of
Comparative Example 1 (formed of SPCC, neither treatment by the
present invention nor ejecting only abrasive is made; hereinafter
called "untreated"): FIG. 3A is an SEM image; FIG. 3B is an EDX
image of silicon (Si); FIG. 3C is an EDX image of carbon (C); and
FIG. 3D is an EDX image of iron (Fe);
[0046] FIGS. 4A to 4D are electron micrographs of a sample of
Comparative Example 2 (formed of SPCC, .theta.=90.degree.): FIG. 4A
is an SEM image; FIG. 4B is an EDX image of carbon (C); FIG. 4C is
an EDX image of silicon (Si); and FIG. 4D is an EDX image of iron
(Fe);
[0047] FIGS. 5A to 5D are electron micrographs of a sample of
Comparative Example 3 (the surface of the sample of Comparative
Example 2 was polished): FIG. 5A is an SEM image; FIG. 5B is an EDX
image of carbon (C); FIG. 5C is an EDX image silicon (Si); and FIG.
5D is an EDX image of iron (Fe);
[0048] FIGS. 6A to 6D are electron micrographs of a sample of
Example 2 (formed of SKD11): FIG. 6A is an SEM image; FIG. 6B is an
EDX image of carbon (C); FIG. 6C is an EDX image of silicon (Si);
and FIG. 6D is an EDX image of iron (Fe);
[0049] FIGS. 7A to 7D are electron micrographs of a sample of
Comparative Example 7 (formed of SKD11, .theta.=90.degree.): FIG.
7A is an SEM image; FIG. 7B is an EDX image of carbon (C); FIG. 7C
is an EDX image of silicon (Si); and FIG. 7D is an EDX image of
iron (Fe);
[0050] FIGS. 8A to 8E are electron micrographs of a sample of
Comparative Example 9 (formed of cemented carbide, 0=90.degree.):
FIG. 8A is an SEM image; FIG. 8B is an EDX image of carbon (C);
FIG. 8C is an EDX image of oxygen (O); FIG. 8D is an EDX image of
aluminum (Al); and FIG. 8E is an EDX image of tungsten (W); and
[0051] FIGS. 9A to 9G are electron micrographs of a sample of
Comparative Example 10 (formed of SKD11 and coated with TiAlN):
FIG. 9A is an SEM image; FIG. 9B is an EDX image of nitrogen (N);
FIG. 9C is an EDX image of aluminum (Al); FIG. 9D is an EDX image
of titanium (Ti); FIG. 9E is an EDX image of iron (Fe); FIG. 9F is
an EDX image of carbon (C); and FIG. 9G is an EDX image of silicon
(Si).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0052] Next, embodiments of the present invention will be
described.
Overview
[0053] A substrate treatment method for a portion to be coated
according to the present invention includes ejecting an elastic
abrasive onto a surface of a workpiece to form irregularities with
a predetermined surface roughness, thereby providing an anchor
effect for a coating to be formed without causing the abrasive
grains to be embedded on the surface of the portion to be coated.
The elastic abrasive includes base material as an elastic body and
abrasive grains compounded and dispersed in the base material as an
elastic body or carried on surfaces of the base material as an
elastic body with, for example, an adhesive.
Workpiece
[0054] The substrate treatment method for the portion to be coated
according to the present invention can be applied to any article
which is to be coated and in which the abrasive grains can be
embedded when they are directly ejected by blasting.
[0055] Articles formed of various materials can be used as the
workpiece in the present invention, including relatively soft,
malleable and ductile metals in which the abrasive grains can
readily be embedded, such as aluminum, copper, brass, and zinc. It
is also possible to use other metals, cemented carbide, which is a
metal composite, semiconductors such as silicon, and engineering
plastics.
[0056] Naturally, the present invention is not suitable for
workpieces formed of hard, brittle materials such as ceramics and
glass because an abrasive is not embedded in such workpieces in
blasting.
Type of Coating to be Formed
[0057] The surface treatment method according to the present
invention may be applied not only to a surface treatment performed
before a coating is formed by CVD or PVD, but also to a surface
treatment performed before a coating is formed by a method such as
electroplating or thermal spraying. As another example, the
substrate treatment method may be applied to a surface treatment
performed before a resin coating is formed by a method such as
coating, as in fluoropolymer coating. Thus, the application of the
method according to the present invention is not limited to any
particular coating method.
[0058] As for the material used to form the coating, the surface
treatment method according to the present invention may be applied
to a surface treatment performed before a hard coating is formed
using, for example, DLC, TiC, TiCN, TiCrN, TiAIN, TiSiN, CrSiN,
CrAlN, CrN, or CrVN, to a surface treatment performed before a
coating of any metal is formed by electroplating or thermal
spraying, or to a surface treatment performed before a resin
coating such as a fluoropolymer coating mentioned above is formed.
Thus, the method of the present invention is independent of the
material of the coating to be formed and can be applied to a
surface treatment performed before forming a coating of any
material.
Elastic Abrasive
[0059] The elastic abrasive used in the present invention includes
the base material as an elastic body and the abrasive grains,
having grinding capability, compounded and dispersed in the base
material as an elastic body or carried on the surfaces of the base
material as an elastic body. When the abrasive collides with the
surface to be processed, the elastic force of the carriers prevents
formation of depressions corresponding to the shape of the elastic
abrasive on the surface being processed and also successfully
prevents the abrasive grains from being embedded therein. The
elastic abrasive absorbs the impact upon collision, thus preventing
the abrasive grains from being embedded. At the same time, the
elastic abrasive cuts the surface of the portion to be coated at
sites where the abrasive grains contained in the elastic abrasive
directly contact the surface of the portion to be coated, thereby
forming irregularities with a predetermined surface roughness.
[0060] In the region where the elastic abrasive of the present
invention collides with the surface of the workpiece, the impact
applied to the sites where the base materials collide with the
surface of the workpiece is cancelled by the elastic force of the
base materials, whereas the sites where the abrasive grains,
dispersed in the base materials, collide with the surface of the
workpiece are exposed to the cutting effect, for example, of the
abrasive grains. Hence, the abrasive of the present invention,
having a relatively large grain size on the whole which is
advantageous in terms of, for example, handling, can be used to
perform the same blasting process as could be performed by ejecting
the abrasive grains dispersed in the base materials alone, without
causing the abrasive grains to be embedded.
[0061] The grain size of the elastic abrasive is not particularly
limited and may be changed according to, for example, the materials
of the elastic abrasive and the workpiece to be processed and the
purpose of processing. As an example, the grain size may be 3 to
0.02 mm. In particular, an elastic abrasive with a small grain size
is effective for cutting or polishing of minute regions.
[0062] An elastic abrasive including fine abrasive grains with an
average grain size of 1 .mu.m (#8,000) or less has the advantage of
effectively utilizing the abrasive grains because the density of
the abrasive grains per unit surface area of the elastic abrasive
can be increased by reducing the grain size of the elastic abrasive
as well.
[0063] The elastic abrasive may contain a colorant, such as a dye
or a pigment, allowing visual determination of the grain size etc.
of the abrasive grains of the elastic abrasive. The elastic
abrasive may also contain a fluorescent colorant, a perfume, or an
antimicrobial agent.
[0064] Next, the base materials and the abrasive grains
constituting the elastic abrasive, the mixing proportion thereof,
and a method for producing the abrasive will be described.
Base Materials
[0065] The abrasive grains, being responsible for the grinding
capability of the elastic abrasive of the present invention, are
carried in the base materials or on the surfaces thereof. The base
materials are formed of an elastic body to prevent the elastic
abrasive from sticking into the portion to be coated, for example,
when the elastic abrasive is ejected onto and collides with the
portion to be coated. The base materials are formed by mixing a raw
material polymer with various additives, as described below.
Raw Material Polymer
[0066] The raw material polymer, serving as the major ingredient,
is mixed with various additives described below to form an elastic
body such as a rubber or a thermoplastic elastomer. The raw
material polymer used may be in solid form or in liquid form, such
as a latex rubber or an emulsion. In terms of the properties of the
raw material polymer, a viscoelastic polymer is preferable to
reduce the impact resilience of the base materials and the abrasive
including the base materials.
[0067] Examples of the rubber include natural rubbers and various
synthetic rubbers such as isoprene rubber, styrene-butadiene
rubber, butadiene rubber, acrylonitrile-butadiene rubber,
chloroprene rubber, ethylene-propylene rubber, chlorosulfonated
polyethylene, chlorinated polyethylene, urethane rubber, silicone
rubber, epichlorohydrin rubber, and butyl rubber.
[0068] An example of the viscoelastic rubber is Norsorex (available
from Elf Atochem, S. A., France), which is a norbornene
polymer.
[0069] Examples of the thermoplastic elastomer include styrene
block copolymer, chlorinated polyethylene elastomer, polyethylene
elastomer, nitrile elastomer, fluoroelastomer, silicone elastomer,
ester-halogen-based polymer alloy, olefinic elastomer, vinyl
chloride elastomer, urethane elastomer, and polyamide
elastomer.
[0070] Examples of the viscoelastic material, in particular,
include polynorbornene (trade name: Norsorex), Sorbothane, silicone
gel, which has a polysiloxane structure, and ethylene-acrylic
elastomer. To attain viscoelasticity, for example, Norsorex may be
used with an aromatic or naphthenic oil and carbon black, serving
as a reinforcing material, added and compounded thereto.
[0071] Such raw material polymers, including rubbers and
thermoplastic elastomers, may be used alone or as a mixture thereof
(used in combination).
[0072] In addition, rubbers and thermoplastic elastomers recycled
from reclaimed waste products or waste materials produced in
manufacturing processes may be used.
Additives
[0073] The raw material polymer is mixed with various additives
before being processed into the base material as an elastic
body.
[0074] When a rubber is used as the raw material polymer, the
rubber polymer is mixed with various additives, such as a
vulcanizing agent for crosslinking rubber molecules, a
vulcanization accelerator for promoting the crosslinking reaction
of the vulcanizing agent, a plasticizer for plasticizing the rubber
to facilitate the mixing and dispersion of the additives and to
increase the ease of processing such as rolling or extrusion, an
adhesion promoter for attaining the adhesiveness required for
rubber manufacture to increase the ease of processing, a filler for
use as an extender to decrease product costs and for improving the
physical properties (e.g., mechanical properties such as tensile
strength and impact resilience) of the rubber and the ease of
processing, and various other additives that are generally used for
rubber forming, such as a stabilizer and a dispersant.
[0075] Examples of the filler used to add the weight of the elastic
abrasive include metals, ceramics, inorganic materials, organic
materials and resins that have lower hardness than the abrasive
grains. Such materials can be added to adjust the density of the
elastic abrasive to a level appropriate for blasting. In addition,
conductive materials such as carbon black and metal particles can
be used to avoid electrostatic charging.
[0076] Although a rubber polymer is used as the raw material
polymer in this embodiment, a thermoplastic elastomer may also be
used, as described above. In this case, various additives generally
used to form thermoplastic elastomers can be used.
Abrasive Grains
[0077] The abrasive grains, which deliver grinding capability
through contact with the workpiece, play a major role in cutting
the surface of the portion to be coated in this method to form
irregularities with a predetermined surface roughness. The abrasive
grains are dispersed in the base materials, formed of the raw
material polymer and the additives, or are carried on the surfaces,
formed in a predetermined shape, of the base materials with, for
example, an adhesive.
[0078] The abrasive grains may be formed of any material that
allows the abrasive grains to be dispersed in or carried on the
base materials and that can be processed to a desired state by
blasting, and various known materials can be used.
[0079] Table 1 below shows examples of materials that can be used
as the abrasive grains.
TABLE-US-00001 TABLE 1 Resins Nylon, polycarbonate, polyethylene,
polypropylene, polystyrene, vinylchloride, polymethyl methacrylate,
polyacetal, and cellulose acetate Plant-based Corn core, seed
shells of walnut, apricot, nut, or peach or the like, pulp, and
cork Metals Oxides of the following metals: iron, aluminum,
silicon, titanium, vanadium, chromium, manganese, cobalt, nickel,
copper, zinc, gallium, germanium, zirconium, niobium, molybdenum,
rhodium, palladium, silver, indium, tin, antimony, and tellurium
Ceramics Glass, quartz, alundum, white alundum, carborundum, green
carborundum, zircon, zirconia, garnet, emery, carbon boride,
titanium boride, aluminum magnesium boride, and boron nitride
Inorganic Calcium carbonate, calcium sulfate, calcium fluoride,
barium sulfate, barium chloride, aluminum sulfate, aluminum
hydroxide, strontium carbonate, strontium sulfate, strontium
chloride, titanium oxide, basic magnesium carbonate, magnesium
hydroxide, carbon, graphite, molybdenum sulfide, and tungsten
sulfide
[0080] In terms of cuttability, the hardness of the abrasive grains
used is preferably equivalent to or higher than that of the
material of the portion to be coated, although the hardness of the
abrasive grains does not necessarily have to be equivalent to or
higher than that of the portion to be coated, depending on, for
example, the type of material of the workpiece and the processing
conditions.
[0081] The irregularities are formed on the portion to be coated by
cutting so that they have a sufficient surface roughness to provide
the anchor effect under the particular conditions, including the
material and thickness of the coating to be formed and the method
for forming the coating. The grain size of the abrasive grains can
be selected based on the irregularities to be formed (surface
roughness).
[0082] Also, the grain size of the abrasive grains is not
particularly limited and may be selected according to, for example,
the final grain size of the abrasive produced with the base
materials. For example, the grain size may be #20 to #20,000 (930
to 0.5 .mu.m). To form a coarser surface, abrasive grains with a
larger grain size (smaller number) may be used.
[0083] The shape of the abrasive grains may be changed according
to, for example, the material of the workpiece and the blasting
conditions. A wide variety of shapes can be used, including
spherical, polygonal, cylindrical, flat, and acicular shapes, and
combinations thereof.
Compounding Ratio
[0084] The mixing proportion (content) of the abrasive grains in
the elastic abrasive preferably ranges from 10% to 90% by weight
based on 100% by weight of the elastic abrasive.
[0085] If the content of the abrasive grains in the elastic
abrasive is 10% by weight or less based on 100% by weight of the
elastic abrasive, the elastic abrasive has high impact resilience
due to the base material as an elastic body and absorbs the impact
upon collision to such an extent that the cutting capability of the
abrasive grains mixed in the base materials is unsatisfactorily
delivered. Another problem occurs that such an elastic abrasive has
low cutting capability, and therefore low processing capability,
because the abrasive grains are present on the surface of the
elastic abrasive at an insufficient density.
[0086] If the content of the abrasive grains is more than 90% by
weight, which is a dominant proportion, the abrasive has low
adhesion between the abrasive grains and the base materials. When
such an elastic abrasive is ejected onto and collides with the
surface to be processed, its collision energy can noticeably crush
the abrasive, and can also embed the abrasive grains of the crushed
abrasive in the portion to be coated.
[0087] More preferably, the mixing proportion of the abrasive
grains in the abrasive can be 60% to 90% by weight based on 100% by
weight of the elastic abrasive. With such a mixing proportion, the
elastic abrasive can be more successfully prevented from being
crushed while its impact resilience and grinding capability are
maintained.
[0088] In particular, dust explosion of a pulverized elastic
abrasive can be prevented if it contains abrasive grains formed of
a material that does not cause dust explosion in an amount of more
than 70% by weight, even if the base materials are formed of a
material that can cause dust explosion.
[0089] In addition, if the abrasive grains of the elastic abrasive
are not only deposited on the surfaces of the base materials, but
are also dispersed in the base materials, the elastic abrasive can
maintain its grinding capability even if the abrasive grains
present on the surfaces of the base materials of the elastic
abrasive are, for example, removed, delaminated, crushed, or worn
by various impacts and frictions occurring in a blasting process,
including ejecting the abrasive onto the workpiece, polishing and
cutting the surface to be processed, and recovering the elastic
abrasive and sieving or dividing its flow path, because the impacts
and frictions in the blasting process also wear and crush the base
materials so that new abrasive grains appear on the surfaces of the
base materials.
[0090] Accordingly, the abrasive of the present invention has
superior durability, does not require the step of regenerating the
elastic abrasive, can withstand extended and repeated use, and is
highly suitable for use in abrasive-circulating processing lines.
The new abrasive grains, as described above, can be made to appear
successfully by adjusting, for example, the amount of wear of the
base materials, the rate of crushing, and the brittleness of the
abrasive. This can be achieved by changing, for example, the
material of the base materials, the mixing proportion (content) of
the abrasive grains in the elastic abrasive, and the production
process.
Production Method
[0091] If the raw material polymer used is the rubber (raw material
rubber) described above, the elastic abrasive of the present
invention can be produced by a known rubber manufacturing
process.
[0092] Rubber products are generally produced through four steps: a
kneading step, a rolling/extruding step, a forming step, and a
vulcanizing step. The method for producing the elastic abrasive of
the present invention will now be described by following these four
steps.
[0093] First, in the kneading step, the raw material rubber is
subjected to mastication (in which a mechanical shear force is
applied to the raw material rubber to, for example, break down
aggregates of molecules and cleave their molecular chains, thereby
adjusting the plasticity and fluidity of the rubber to those
appropriate for mixing of the additives and forming) and is then
subjected to compounding (in which the masticated raw material
rubber is mixed with the additives with a mechanical shear force
applied to plasticize the rubber and to disperse the additives in
the rubber). In the present invention, the abrasive grains are
compounded together with the additives, such as a vulcanizing agent
and a filler, in the kneading step so that the resultant abrasive
has the abrasive grains dispersed in the base materials.
[0094] The mastication and compounding in the kneading step may be
performed using any known kneading machine, such as an internal
mixer, as typified by a Banbury mixer, an open roll mill, a
kneader, or a stirrer capable of kneading while using shear
force.
[0095] Next, in the rolling/extruding step, the raw material
prepared by kneading the raw material rubber together with the
additives and the abrasive grains to an appropriate plasticity is
processed into a shape that is formable in the subsequent forming
step, such as a plate, sheet, or lump shape.
[0096] The apparatus used in this step may be, for example, a
calender, which includes an array of rollers, or an extruder, which
includes a screw.
[0097] The raw material processed into an appropriate shape in the
rolling/extruding step, as described above, is formed into a
predetermined size and shape in the forming step. To process the
raw material with a shape such as a plate, sheet, or lump shape
into fine grains for the production of the abrasive in the present
invention, the raw material is crushed into pellets that are
screened to a predetermined grain size. The crushing can be
performed using any known crushing machine.
[0098] Subsequently, the grains prepared in the forming step are
heated in the vulcanizing step, where the vulcanizing agent
contained in the grains induces a crosslinking reaction to
vulcanize the base materials, but not the abrasive grains, into an
elastic body. In the vulcanizing step, any known apparatus such as
a press, a vulcanizing pan, or a continuous extrusion vulcanizer
may be used.
[0099] The grain formation (forming step) and the vulcanization by
crosslinking (vulcanizing step) may be reversed in order. For
example, the raw material processed into an appropriate shape in
the rolling/extruding step may be directly transferred to the
vulcanizing step and be vulcanized into an elastic body before
being crushed into grains in the forming step.
[0100] If the raw material polymer used is a thermoplastic
elastomer, the elastic abrasive can be produced by a known
thermoplastic-elastomer manufacturing process. An abrasive with a
desired grain size can be produced through a kneading step in which
the raw material polymer is subjected to mastication and
compounding with the additives and the abrasive grains, a forming
step in which the kneaded raw material is melted by being heated
above its melting point and is, for example, extruded or injected,
and a crushing step in which the elastic body thus formed is
crushed and screened to a predetermined grain size. In the kneading
step, a roll mill, a pressure kneader, or an internal mixer, for
example, may be used.
[0101] If the abrasive to be produced has the abrasive grains
carried on the surfaces of the base materials, an adhesive, for
example, may be used to deposit the abrasive grains on surfaces of
base materials having no abrasive grains mixed or dispersed therein
and formed into a predetermined shape.
Ejection Method
[0102] The abrasive may be ejected onto the surface of the
workpiece together with a compressed fluid such as compressed air
or, as described above, may be ejected by a centrifugal force from
a rotating impeller or may be hit and ejected by an impact rotor.
Thus, the ejection method used may be any method that allows the
ejection of the abrasive under desired conditions.
[0103] In this embodiment, the abrasive is ejected by the ejection
method using a compressed fluid, particularly, compressed air,
because the ejection speed of the abrasive, for example, can be
controlled relatively easily.
[0104] The abrasive is preferably ejected onto the portion to be
coated at an acute incident angle (less than 90.degree.), more
preferably 60.degree. or less, still more preferably 45.degree. or
less.
[0105] The incident angle of the abrasive is preferably oblique
with respect to the workpiece because, as shown in FIG. 1, the
force component, Vsin .theta., exerted in such a direction as to
embed the abrasive colliding with the surface of the workpiece in
the surface of the workpiece is decreased with decreasing incident
angle .theta. of the abrasive colliding with the surface of the
workpiece. Hence, the abrasive grains carried on the base material
as an elastic body can more reliably be prevented from being
embedded in the surface of the workpiece under a synergistic effect
provided by reducing the incident angle .theta., as described
above.
EXAMPLES
[0106] Next, the results of tests for comparison of workpieces
subjected to substrate treatment by the method of the present
invention, as well as those after coatings were formed thereon,
with workpieces subjected to substrate treatment by a known
blasting method, as well as those after coatings were formed
thereon, will be shown.
Examination of Embedded Abrasive Grains
[0107] Next, the results of examination of embedded abrasive grains
on workpieces formed of various materials and subjected to
different substrate treatments, including samples subjected to
substrate treatment by the method of the present invention,
untreated samples, and samples subjected to substrate treatment by
a typical blasting method, will be shown below.
[0108] Cold-Rolled Steel Sheet (SPCC) Treatment Test
[0109] Processing Conditions
Example
[0110] The substrate treatment method (Example) of the present
invention was performed under the conditions shown in Table 2
below.
TABLE-US-00002 TABLE 2 Processing Conditions for Substrate
Treatment under the present Invention (Example 1-4) Example 1
Example 2 Example 3 Example 4 Workpiece Cold-Rolled Alloy Tool
Steel Cemented Carbide Aluminum Steel Sheet (SKD11) (KHO3)
manufactured by (A1100) (SPCC) Sumitomo Electric Industries, Ltd.
Blasting "FDQ-SR" "SG-SR" "SG-SR" "LDQ-SR" Machine Fuji Mfng.
Ejection Method Direct-pressure Gravity Gravity Direct-pressure
(Blower) Compressed air Compressor Compressor Compressor Blower
Supply method Condition Of Ejection Pressure (MPa) 0.3 0.2 0.5 0.02
Ejection 70 50 100 50 distance(mm) Incident angle .theta..degree.
30 45 60 75 Nozzle-tip 8 10 6 10 diameter(mm) Ejection material
Abrasive grains compounded and dispersed in the base material
Elastic abrasive Average 650 35 350 1000 grain size Minimum (.mu.m)
500 20 200 800 Maximum (.mu.m) 800 50 500 1200 Base material Rubber
Abrasive grains "Fujilundum GC" "Fujilundum GC" "Fujilundum WA"
"Fujilundum GC" Fuji Mfng. (green carborundum) (green carborundum)
(white alundum) (green arborundum) Mesh #1000 #320 #320 #10000
Average size (.mu.m) (12) (40) (40) (1)
Comparative Examples
[0111] As Comparative Examples, blasting was performed using
abrasive grains alone under the conditions shown in Table 3
below.
TABLE-US-00003 TABLE 3 Blasting conditions for Comparative Example
1 Blasting Machine "SGF-4" manufactured by Fuji Mfng. Gun "F2-4
type" nozzle-tip diameter of 8 mm Condition Of Ejection Pressure of
0.3 Mpa Incident angle .theta..degree. Ejection distance of 70 mm,
90.degree. (Comparative Example 2) 45.degree. (Comparative Example
2) 30.degree. (Comparative Example 5) Ejection material "Fujilundum
GC" manufactured by Fuji Mfng. (Green Carborundum), #1000 (average
grain size of 12 .mu.m) only Processing Method Manual Comparative
Example 3 Sample of Comparative Example 2 whose surface is cut
Comparative Example 6 Untreated SKD11 Steel Comparative Example 7
Blasting of Comparative Example 1 against SKD11 steel Comparative
Example 8 Untreated Cemented Carbide ("KH03" manufactured by
Sumitomo Electric Industries, Ltd.) Comparative Example 9 Blasting
of Comparative Example 1 to the Cemented Carbide of Comparative
Example 8 Comparative Example 10 Processing GC abrasives of #320 by
the method of Comparative Example 1 at an incident angle of .theta.
90.degree.
Test Method
[0112] The surfaces of the workpieces subjected to blasting under
the processing conditions shown in Table 2 were exposed to a blast
compressed air to remove deposits and were dipped in isopropyl
alcohol (IPA) and subjected to ultrasonic cleaning for ten (10)
minutes. The surfaces of the individual samples were examined by
electron microscopy and X-ray spectroscopy.
[0113] The surface examination by electron microscopy was performed
using the scanning electron microscope (SEM) "S-3400N"
(manufactured by Hitachi, Ltd.). The X-ray spectroscopy was
performed by energy dispersive X-ray spectroscopy (EDX; using INCA
Energy 7021 manufactured by Oxford Instruments), in which the
samples were irradiated with an electron beam, various X-rays
generated from the samples were detected, its spectrum was
displayed after segmentation using a pulse-height analyzer, and
elements were identified and quantified from the spectrum.
[0114] The SEM and the EDX were both performed with an acceleration
voltage of 15 eV. In the EDX, element analysis was performed on the
surfaces of the samples by element mapping to identify the
materials present thereon.
[0115] To examine the presence of green carborundum (GC) abrasive
grains (formed of SiC), three elements, namely, iron (Fe), which is
a constituent element of the workpiece material (SPCC), and silicon
(Si) and carbon (C), which are constituent elements of GC (SiC),
were selected for element identification.
Test Results
[0116] The workpiece used was a cold-rolled steel sheet (SPCC)
having a size of 100.times.100 mm and a thickness of 3 mm. Samples
were prepared by blasting the surface of the workpiece with the
elastic abrasive (Example 1; see Table 2), without treatment
(Comparative Example 1), by blasting the surface of the workpiece
with abrasive grains at an incident angle .theta. of 90.degree.
(Comparative Example 2), 45.degree. (Comparative Example 4), or
30.degree. (Comparative Example 5) (see Table 3), and by cutting
the surface of the sample prepared in Comparative Example 2
(.theta.=90.degree.) (Comparative Example 3).
[0117] FIGS. 2A to 2D show an SEM image and EDX mapping images of
the sample of Example 1. FIGS. 3A to 3D, 4A to 4D, and 5A to 5D
show SEM images and EDX mapping images of the samples of
Comparative Examples 1 to 3, respectively.
[0118] Table 4 shows the correspondences between the samples and
FIGS. 2A to 2D, 3A to 3D, 4A to 4D, and 5A to 5D.
TABLE-US-00004 TABLE 4 Relation between each samples and drawings
Corresponding Sample Name Processing Conditions Drawings Example 1
Blasting by elastic abrasives FIG. 2 Comparative Example 1
Untreated article FIG. 3 Comparative Example 2 Blasting by abrasive
grains FIG. 4 (.theta. = 90.degree.) Comparative Example 3 Abrading
the surface of FIG. 5 Comparative Example 2
[0119] According to the EDX images (element mapping images) of
Example 1, as shown in FIGS. 2B to 2D, iron (Fe), silicon (Si), and
carbon (C) were all uniformly distributed over the surface of the
sample of Example 1, and no localized distribution of silicon (Si)
or carbon (C) was found.
[0120] FIGS. 3B to 3D show the EDX images of the untreated SPCC of
Comparative Example 1. According to these images, iron (Fe),
silicon (Si), and carbon (C) were all uniformly distributed.
[0121] These results demonstrate that the uniform distribution of
silicon (Si) in the EDX image of Example 1 was due to the silicon
(Si) inherent in the workpiece, namely, SPCC. This confirms that
the abrasive grains compounded and dispersed in the elastic
abrasive were not embedded in the surface of the workpiece, namely,
SPCC, for the sample of Example 1, in which no localized
distribution of silicon (Si) or carbon (C) was found.
[0122] Of the samples of the Comparative Examples, which were
directly blasted with the GC abrasive grains (#1,000), the sample
of Comparative Example 2, in which the incident angle .theta. was
90.degree., had a localized distribution of silicon (Si), as shown
in FIG. 4C (circled regions). According to the iron (Fe) EDX image
(see FIG. 4D), however, no localization of iron (Fe) was found at
sites (circled regions) corresponding to the localized silicon
(Si).
[0123] According to the results, the material of the abrasive
grains, namely, SiC, remained on the processed surface of the
sample of Comparative Example 2 after the cleaning using a blast of
compressed air and the ultrasonic cleaning following the ejection
of the abrasive grains. This demonstrates that the abrasive grains
were embedded. Carbon (C) was nearly uniformly distributed because
it was also contained in the treated steel (SPCC).
[0124] FIGS. 5A to 5D show the SEM and EDX images of the sample of
Comparative Example 3, in which the surface of the sample of
Comparative Example 2 was polished using diamond abrasive grains
(#10,000; grain size: 1 .mu.m).
[0125] As shown in FIGS. 5A to 5D, the abrasive grains, namely,
SiC, embedded in the surface of the sample, were exposed by
polishing the surface Comparative Example 2. This demonstrates that
the abrasive grains were embedded in the surface of the workpiece
when they were directly ejected.
[0126] The surface polishing with the diamond abrasive grains was
performed using the blasting apparatus "LDQSR-3", manufactured by
Fuji Manufacturing Co., Ltd., at an ejection pressure of 0.06 MPa
and a nozzle-tip diameter of 10 mm.
[0127] According to the EDX results, the silicon (Si)
concentrations of the samples of Example 1, Comparative Example 1
(untreated SPCC), and Comparative Example 2 were 0.29 atomic
percent, 0.31 atomic percent, and 7.5 atomic percent, respectively.
These results, in terms of atomic percent, demonstrate that the
sample of Example 1 had no abrasive grains embedded.
[0128] According to the SEM and EDX images (not shown) of the
samples blasted with the adhesive grains at incident angles .theta.
of 45.degree. (Comparative Example 4) and 30.degree. (Comparative
Example 5), the material of the abrasive grains, namely, SiC, was
found to be present, indicating that the abrasive was embedded.
Thus, the embedding of the abrasive could not be prevented simply
by adjusting the incident angle .theta. of the abrasive grains with
respect to the workpiece.
Alloy Tool Steel (SKD II) Treatment Test
[0129] Processing Conditions and Test Method
[0130] A sample (Example 2) formed of alloy tool steel (SKD11) and
subjected to substrate treatment by the method of the present
invention, untreated SKD11 (Comparative Example 6), and a sample
(Comparative Example 7) formed of SKD11 and subjected to blasting
by ejecting abrasive grains were examined for abrasive grains
embedded in the surfaces of the samples.
[0131] The processing conditions of Example 2 were as shown in
Table 2, and the test method of Example 2 and the processing
conditions and the test method of Comparative Example 7 were
identical to those of Example 1 and Comparative Example 2,
respectively, except that the workpiece was formed of a different
material.
[0132] Test Results
[0133] According to the EDX results, the silicon (Si) concentration
(%) of the sample of Comparative Example 7, in which the treatment
was performed by ejecting abrasive grains, was 11.8 atomic percent,
whereas those of Example 2, in which the substrate treatment was
performed by the method of the present invention, and Comparative
Example 6, in which no treatment was performed, were both 0.6
atomic percent.
[0134] Thus, the silicon (Si) concentration (%) of the sample of
Example 2 was similar to that of the untreated sample (Comparative
Example 6). This measurement of silicon (Si) concentration
demonstrates that the GC abrasive grains (formed of SiC) were not
embedded.
[0135] Also, from an SEM image of Example 2 shown in FIG. 6A and
EDX images shown in FIGS. 6B to 6D, the silicon (Si) distribution
was a similar map to those in EDX images (not shown) of the
untreated SKD11 (Comparative Example 6).
[0136] These results demonstrate that no abrasive grains were
embedded in the surface of the sample of Example 2, which was a
condition resembling the surface of the untreated SKD11
(Comparative Example 6).
[0137] According to an SEM image shown in FIG. 7A and EDX images
shown in FIG. 7B to 7D, on the other hand, silicon (Si) was
localized on the surface of the sample of Comparative Example 7, in
which the abrasive grains were ejected. This demonstrates that the
ejected abrasive grains were embedded in the surface of the
workpiece, namely, SKD11.
[0138] Treatment Test for Cemented Carbide ("KH03" manufactured by
Sumitomo Electric Industries, Ltd.)
Processing Conditions and Test Method
[0139] A sample (Example 3) formed of a cemented carbide ("KH03"
manufactured by Sumitomo Electric Industries, Ltd.) and subjected
to substrate treatment by the method of the present invention, an
untreated cemented carbide (Comparative Example 8), and a sample
(Comparative Example 9) formed of the cemented carbide and
subjected to blasting by ejecting abrasive grains were examined for
abrasive grains embedded in the surfaces of the samples.
[0140] The processing conditions and the test method of Example 3
were as shown in Table 2.
[0141] The processing conditions and the test method of Comparative
Example 9 were identical to those of Comparative Example 2 except
that the workpiece was formed of a different material and that the
abrasive grains ejected were Fujilundum WA #320 (formed of white
alundum; manufactured by Fuji Manufacturing Co., Ltd.).
[0142] Test Results
[0143] FIGS. 8A to 8E show SEM and EDX images of the sample of
Comparative Example 9, in which the abrasive grains formed of white
alundum (formed of Al.sub.2O.sub.3) were ejected onto the cemented
carbide, namely, tungsten carbide (WC).
[0144] As shown in FIGS. 8A to 8E, element mapping of aluminum (Al)
and oxygen (O), which are constituent elements of the material of
the abrasive grains, namely, aluminum oxide (Al.sub.2O.sub.3), gave
EDX images corresponding to its SEM image. This demonstrates that
the abrasive grains remained on the surface.
[0145] The surface of the sample of Comparative Example 9 was
slightly polished using an elastic abrasive including base material
as an elastic body and diamond abrasive grains (#10,000) compounded
and dispersed therein. This revealed that the abrasive grains were
embedded in the surface of the treated cemented carbide.
[0146] For the sample of Example 3, in which the cemented carbide
was subjected to the substrate treatment by the method of the
present invention, no embedded abrasive grains were found in SEM
and EDX images (not shown).
[0147] Coating Test
[0148] As a coating test, a TiAIN coating, which is a hard coating,
was formed on a workpiece formed of SKD11 by a plasma process.
[0149] A sample of Example 2 was prepared by blasting the
substrate, formed of SKD11, with an elastic abrasive including base
material as an elastic body and Green Carborundum (GC) abrasive
grains (#320) compounded and dispersed therein under the conditions
shown in Table 2 before forming the coating.
[0150] A sample of Comparative Example 10 was prepared by directly
ejecting Green Carborundum (GC) abrasive grains (#320) onto the
surface of the workpiece at an incident angle .theta. of 90.degree.
before forming the coating. The ejection conditions were as shown
in Table 3.
[0151] After the TiAIN coatings were formed on the surfaces of the
samples, the surfaces were treated by slightly polishing them using
an elastic abrasive including base material as an elastic body and
diamond abrasive grains (#10,000) compounded and dispersed therein
to, for example, remove droplets on the coatings.
[0152] The samples of Example 2 thus prepared were examined for
surface conditions and element distribution based on SEM and EDX
images. According to the EDX images (not shown), only titanium,
aluminum, and nitrogen were detected on the surface of the coating
formed on the sample of Example 4. This demonstrates that a uniform
TiAIN coating was formed on the surface.
[0153] According to the EDX images shown in FIGS. 9B to 9G, on the
other hand, silicon (Si), which is a component of the abrasive, was
strongly detected on the coating formed on the sample of
Comparative Example 10, in which the substrate treatment was
performed by directly ejecting the abrasive grains (see the circled
region in FIG. 9G).
[0154] In the region where silicon (Si) was strongly detected,
titanium, aluminum, and nitrogen, which are constituent elements of
the coating, were detected in decreased amounts (see FIGS. 9B to
9D). This demonstrates that no coating was formed in the region
where silicon (Si), which is a component of the abrasive grains,
was detected, that is, a region where an abrasive grain was
embedded by blasting.
[0155] The region where little coating was formed occurred because
the Green Carborundum (GC) abrasive grains (formed of SiC), which
are insulating, were embedded in the substrate and caused a
different voltage to be applied compared with other regions.
[0156] Also, the SEM image confirms that little TiAIN coating was
formed in the region where silicon (Si) was strongly detected.
[0157] The above results demonstrate that the substrate treatment
based on the method of the present invention, in which the base
material as an elastic body having the abrasive grains compounded
and dispersed therein are ejected onto a workpiece, is more
effective in forming a uniform coating than a substrate treatment
based on a known blasting method in which abrasive grains are
directly ejected onto a workpiece.
[0158] Friction Test
[0159] The samples thus prepared, namely, the sample of Example 2,
in which the TiAlN coating was formed on the surface of the
substrate formed of SKD11, and the sample of Comparative Example
10, were subjected to a friction test to compare the two samples
for durability.
[0160] This friction test was a ball-on-disk test (the apparatus
used was manufactured by Rhesca Co., Ltd.), in which friction was
caused against a ball-shaped test piece, namely, a stainless steel
(SUS304) ball having a diameter of 3/16 inches.
[0161] Before the test was started, the samples and the ball
against which friction was caused were dipped in acetone and were
subjected to ultrasonic cleaning to remove contaminants.
[0162] According to the results of the above friction test, the
duration for which the friction coefficient of the sample of
Example 2 remained stable was measured to be 20, with that of the
sample of Comparative Example 10 being 1 (Comparative Example 10:
Example 2=1:20), that is, 20 times the duration for which the
friction coefficient of the sample of Comparative Example 10
remained stable.
[0163] The coating formed on the sample of Example 4 was found to
remain stably laminated after the friction test and showed
excellent results for coating adhesion strength, whereas the
coating formed on the sample of Comparative Example 10 was found to
be delaminated and could no longer be used as a coating.
[0164] Thus the broadest claims that follow are not directed to a
machine that is configure in a specific way. Instead, said broadest
claims are intended to protect the heart or essence of this
breakthrough invention. This invention is clearly new and useful.
Moreover, it was not obvious to those of ordinary skill in the art
at the time it was made, in view of the prior art when considered
as a whole.
[0165] Moreover, in view of the revolutionary nature of this
invention, it is clearly a pioneering invention. As such, the
claims that follow are entitled to very broad interpretation so as
to protect the heart of this invention, as a matter of law.
[0166] It will thus be seen that the objects set forth above, and
those made apparent from the fore going description, are
efficiently attained and since certain changes may be made in the
above construction without departing from the scope of the
invention, it is intended that all matters contained in the
foregoing description or shown in the accompanying drawings shall
be interpreted as illustrative and not in a limiting sense.
[0167] It is also to be understood that the following claims are
intended to cover all of the generic and specific features of the
invention herein described, and all statements of the scope of the
invention which, as a matter of language, might be said to fall
therebetween.
[0168] Now that the invention has been described;
* * * * *