U.S. patent application number 14/352216 was filed with the patent office on 2014-09-18 for biocompatible co-cr-mo alloy.
This patent application is currently assigned to KYOCERA Medical Corporation. The applicant listed for this patent is KYOCERA Medical Corporation, NATIONAL UNIVERSITY CORPORATION TOKYO MEDICAL AND DENTAL UNIVERSITY. Invention is credited to Takao Hanawa, Naoyuki Nomura.
Application Number | 20140271317 14/352216 |
Document ID | / |
Family ID | 48140982 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140271317 |
Kind Code |
A1 |
Nomura; Naoyuki ; et
al. |
September 18, 2014 |
BIOCOMPATIBLE Co-Cr-Mo ALLOY
Abstract
The present invention is to provide a Co--Cr--Mo alloy excellent
in mechanical properties such as yield strength and tensile
strength. The present invention is a biocompatible Co--Cr--Mo alloy
comprising, in mass %, more than 30% and not more than 36% of Cr, 5
to 8% of Mo, 0.20 to 0.65% of N, and the balance consisting of Co
and inevitable impurities, and produced by layered manufacturing.
The biocompatible Co--Cr--Mo alloy of the present invention
preferably has a solidification structure of a dendrite structure
and the primary arm spacing of the dendrite structure is not more
than 5 .mu.m.
Inventors: |
Nomura; Naoyuki; (Bunkyo-ku,
JP) ; Hanawa; Takao; (Bunkyo-ku, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KYOCERA Medical Corporation
NATIONAL UNIVERSITY CORPORATION TOKYO MEDICAL AND DENTAL
UNIVERSITY |
Osaka
Tokyo |
|
JP
JP |
|
|
Assignee: |
KYOCERA Medical Corporation
Osaka
JP
NATIONAL UNIVERSITY CORPORATION TOKYO MEDICAL AND DENTAL
UNIVERSITY
Tokyo
JP
|
Family ID: |
48140982 |
Appl. No.: |
14/352216 |
Filed: |
October 18, 2012 |
PCT Filed: |
October 18, 2012 |
PCT NO: |
PCT/JP2012/076999 |
371 Date: |
April 16, 2014 |
Current U.S.
Class: |
419/1 ;
75/246 |
Current CPC
Class: |
C22C 19/07 20130101;
C22C 1/0433 20130101; Y02P 10/25 20151101; Y02P 10/295 20151101;
B22F 3/1055 20130101; A61L 27/047 20130101; A61L 27/045 20130101;
A61L 31/022 20130101 |
Class at
Publication: |
419/1 ;
75/246 |
International
Class: |
C22C 19/07 20060101
C22C019/07; B22F 3/105 20060101 B22F003/105 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 21, 2011 |
JP |
2011-231703 |
Claims
1. A biocompatible Co--Cr--Mo alloy comprising, in mass %, more
than 30% and not more than 36% of Cr, 5 to 8% of Mo, 0.20 to 0.65%
of N, and the balance consisting of Co and inevitable impurities,
and produced by layered manufacturing.
2. The biocompatible Co--Cr--Mo alloy according to claim 1, wherein
a solidification structure is a dendrite structure, and the primary
arm spacing of the dendrite structure is not more than 5 .mu.m.
3. The biocompatible Co--Cr--Mo alloy according to claim 1, wherein
the 0.2% proof stress is not less than 700 MPa and the tensile
strength is not less than 980 MPa.
4. A biocompatible Co--Cr--Mo alloy powder used for producing the
biocompatible Co--Cr--Mo alloy according to claim 1, having a
particle diameter of not more than 100 .mu.m.
5. A process for producing an biocompatible Co--Cr--Mo alloy,
wherein the Co--Cr--Mo alloy powder according to claim 4 is
layered-manufactured.
6. The process for producing an biocompatible Co--Cr--Mo alloy
according to claim 5, wherein the layered manufacturing is carried
out by irradiating laser of an output power of not less than 50 W
and adjusting the scan pitch in the plane direction to be not less
than 0.1 mm.
Description
TECHNICAL FIELD
[0001] The present invention relates to a biocompatible Co alloy,
and particularly to a Co--Cr--Mo alloy excellent in mechanical
properties, particularly, proof stress, tensile strength, and the
like.
BACKGROUND ART
[0002] Co--Cr--Mo alloys have been used widely all over the world
as a biocompatible material and, for example, a Co-28% Cr-6% Mo
alloy (casting material) standardized as ASTM F75 has been known.
However, the cast material standardized as ASTM F75 is difficult to
sufficiently suppress solidification defects and segregation as it
is and there is room for improvement of strength and ductility.
[0003] In order to solve such problems of the material standardized
as ASTM F75, for example, Patent Document 1 proposes a casting
material of a Co--Cr--Mo alloy with increased contents of Cr and
nitrogen as compared with the above-mentioned standardized
material.
PRIOR ART DOCUMENT
Patent Document
[0004] Patent Document 1: JP-A-2009-114477
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0005] According to the above-mentioned Patent Document 1, it is
described that a cast Co alloy containing, in mass %, more than 30%
and not more than 36% of Cr, 5 to 8% of Mo, and 0.20 to 0.65% of N
has improved yield strength, tensile strength, and elongation as
compared with the material standardized as ASTM F75.
[0006] In Patent Document 1, an ingot of a Co--Cr--Mo type alloy is
produced by metal mold casting and mechanical properties thereof
are measured. However, according to the investigations carried out
by the inventors of the present invention, in the case where the
Co--Cr--Mo type alloy described in Patent Document 1 is produced by
sand mold casting which is employed most practically in
biomaterials, it is supposed that the mechanical properties as
disclosed in Cited Document 1 cannot necessarily be realized. Here,
from the viewpoint of particularly high strength, it is generally
effective to carry out hot processing such as hot rolling or hot
forging. However, the Co--Cr--Mo alloy with the composition
described in Patent Document 1 is poor in the hot processability
and difficult to have high strength by hot processing and thus it
is difficult to obtain a Co--Cr--Mo alloy excellent in yield
strength, tensile strength and the like.
[0007] Accordingly, the present invention aims to provide a
Co--Cr--Mo alloy excellent in mechanical properties such as yield
strength (0.2% proof stress) and tensile strength.
Means for Solving the Problems
[0008] The present invention which has achieved the above-mentioned
problem is a biocompatible Co--Cr--Mo alloy comprising, in mass
%,
[0009] more than 30% and not more than 36% of Cr,
[0010] 5 to 8% of Mo,
[0011] 0.20 to 0.65% of N, and the balance consisting of Co and
inevitable impurities, and
[0012] produced by layered manufacturing.
[0013] The biocompatible Co--Cr--Mo alloy of the present invention
preferably has a solidification structure of a dendrite structure
and the primary arm spacing of the dendrite structure is not more
than 5 .mu.m. The biocompatible Co--Cr--Mo alloy of the present
invention has the 0.2% proof stress of not less than 700 MPa and
the tensile strength of not less than 980 MPa, for example.
[0014] The present invention also comprises a powder to be used for
producing the biocompatible Co--Cr--Mo alloy. The powder has a gist
for having a particle diameter of not more than 100 .mu.m.
[0015] The present invention also comprises a process for producing
a Co--Cr--Mo alloy wherein the Co--Cr--Mo alloy having the
above-described chemical composition is layered-manufactured.
[0016] In the production process of the present invention, layered
manufacturing is preferably carried out by irradiating laser of an
output power of not less than 50 W and adjusting the scan pitch in
the plane direction to be not less than 0.1 mm. As well, the scan
pitch in the plane direction means a irradiation spacing of
laser.
Effects of the Invention
[0017] According to the present invention, a Co--Cr--Mo alloy
excellent in 0.2% proof stress, tensile strength, and elongation is
provided since a Co--Cr--Mo alloy with high Cr and high N is
produced by layered manufacturing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] [FIG. 1] FIG. 1 is a graph illustrating a relationship
between the scan pitch in the plane direction and 0.2% proof
stress.
[0019] [FIG. 2] FIG. 2 is a graph illustrating a relationship
between the output power of laser, and tensile strength and
elongation.
[0020] [FIG. 3] FIG. 3 is an optical microscope photograph obtained
by observing the structure of a Co alloy produced in the Examples
described later.
MODE FOR CARRYING OUT THE INVENTION
[0021] The inventors of the present invention repeatedly made
investigations to provide a Co--Cr--Mo alloy excellent in
mechanical properties such as yield strength and tensile strength
and found that a Co--Cr--Mo alloy excellent in 0.2% proof stress,
tensile strength and elongation is obtained by powdering a
Co--Cr--Mo alloy with a composition described in Patent Document 1
and carrying out layered manufacturing of the powder, and the
finding now lead to completion of the present invention.
Hereinafter, the alloy composition of the present invention and
layered manufacturing will be described in order.
[0022] A Co--Cr--Mo alloy of the present invention contains, in
mass %, more than 30% and not more than 36% of Cr, 5 to 8% of Mo,
and 0.20 to 0.65% of N.
[0023] Cr is an element indispensable for surely attaining
corrosion resistance. In the present invention, the mechanical
properties are further improved and the amount of dissolved N is
increased by adjusting the Cr amount to be more than 30% (it means
mass %, hereinafter the same in the chemical composition). The Cr
amount is preferably not less than 31% and more preferably not less
than 32%. On the other hand, if the Cr amount is excessive, the
mechanical properties such as tensile strength and elongation are
rather deteriorated. Therefore, the Cr amount is determined to be
not more than 36% in the present invention. The Cr amount is
preferably not more than 35% and more preferably not more than
34%.
[0024] Mo is an element effective for improvement of corrosion
resistance and wear resistance. Therefore, the Mo amount is
determined to be not less than 5%. The Mo amount is preferably not
less than 6%. On the other hand, if the Mo amount is excessive, it
results in deterioration of processability. Therefore, the Mo
amount is determined to be not more than 8%. The Mo amount is
preferably not more than 7%.
[0025] N is an element for forming a stable .gamma. phase and
having an action of improving ductility. N is an element also
having an action of improving the 0.2% proof stress. Therefore, the
N amount is determined to be not less than 0.20% in the present
invention. The N amount is preferably not less than 0.25% and more
preferably not less than 0.30%. On the other hand, if the N amount
is excessive, Cr.sub.2N is precipitated and mechanical properties
are deteriorated. Therefore, the N amount is determined to be not
more than 0.65%. The N amount is preferably not more than 0.60% and
more preferably not more than 0.55%.
[0026] The composition of the Co alloy of the present invention is
as described above and the balance is made up by substantially Co.
Co is an element having corrosion resistance and wear resistance.
In addition, it is naturally allowed that the Co alloy of the
present invention contain inevitable impurities brought into
depending on the raw materials, resources, the situation of
production equipment, and the like. Further, in the present
invention, if necessary, the Co alloy may contain at least one
element selected from the group consisting of not more than 0.2% of
C, not more than 1.00% of Ni, not more than 1.00% of Si, and not
more than 1.00% of Mn.
[0027] The Co alloy of the present invention is characterized by
being produced by layered manufacturing. The Co alloy produced by
layered manufacturing has a fine solidification structure and in
general, the solidification structure is a dendrite structure, and
the primary arm spacing of the dendrite structure is, for example,
not more than 5 .mu.m and preferably not more than 1.5 .mu.m. The
lower limit of the arm spacing is generally around 0.5 .mu.m.
[0028] Next, the layered manufacturing will be described. The
layered manufacturing is described in, for example, Japanese Patent
No. 4054075, and is a method for producing a compact by spreading a
material powder in a layer form, melting and thereafter solidifying
the material powder by irradiating the powder with electromagnetic
radiation such as laser beam or corpuscular radiation such as
electron beam. In the present invention, since the Co alloy with
the above-mentioned composition is obtained by layered
manufacturing, it is made possible to provide the Co alloy
excellent in elongation in addition to 0.2% proof stress, tensile
strength. Further, by layered manufacturing, the irradiation
pattern of the radial rays is precisely controlled and therefore,
shaping into a complicated shape is made possible.
[0029] According to the investigations made by the inventors of the
present invention, there is a correlation between the mechanical
properties (0.2% proof stress, tensile strength, and elongation) of
a Co alloy and the condition of the layered manufacturing, and
particularly the 0.2% proof stress is more improved by widening the
scan pitch in the plane direction and particularly the tensile
strength and elongation is more improved by increasing the output
power of the radial rays. Concretely, the scan pitch in the plane
direction is preferably adjusted to be not less than 0.1 mm, more
preferably not less than 0.2 mm, and even more preferably not less
than 0.3 mm. The upper limit of the scan pitch in the plane
direction is, for example, not more than 0.5 mm for preventing pore
formation. The output power of the radial rays is preferably not
less than 50 W, more preferably not less than 100 W, and even more
preferably not less than 150 W. Although it depends on the
apparatus for outputting the radial rays, the upper limit of the
output power of the radial rays is, for example, not more than 400
W.
[0030] Other production conditions for the layered manufacturing
may be set properly and, for example, the radiation diameter (e.g.,
radius of circle) of radial rays may be adjusted to be about 0.1 to
1 mm; the distance from the radial ray source to the material
powder may be adjusted to be about 100 to 10000 mm; and the layer
thickness (thickness of one layer of the powder) may be adjusted to
be about 0.01 to 0.1 mm. The atmosphere at the time of the layered
manufacturing is also not particularly limited, and it is
preferable to carry out the layered manufacturing in an atmosphere
of an inert gas such as argon gas or nitrogen gas.
[0031] The material powder used for the layered manufacturing can
be prepared by an atomization method (water atomization method or
gas atomization method), a rotating electrode process, a ball mill
method, and the like. It is preferable that the powder prepared by
the above-mentioned method is sieved if necessary to have a
particle diameter of not more than 100 .mu.m (preferably not more
than 70 .mu.m, and more preferably not more than 50 .mu.m). In
addition, the particle diameter of the material powder is generally
not below 5 .mu.m. In this description, the particle diameter means
the maximum diameter.
[0032] The type of radial rays in the layered manufacturing is not
particularly limited, but laser of electromagnetic radiation is
employed in the present invention. Examples of the type of laser
include YAG laser, excimer laser, semiconductor laser, and CO.sub.2
laser.
[0033] The Co alloy of the present invention produced by
layered-manufacturing the Co alloy with the above-mentioned
composition is excellent in mechanical properties such as 0.2%
proof stress, tensile strength, and elongation. The 0.2% proof
stress is, for example, not less than 700 MPa (preferably not less
than 730 MPa and more preferably not less than 7 60 MPa) and the
tensile strength is, for example, not less than 980 MPa (preferably
not less than 1000 MPa and more preferably not less than 1020 MPa).
The elongation (total elongation) is, for example, not less than
8.0% (preferably not less than 10.0% and more preferably not less
than 15.0%).
[0034] The structure of the Co alloy of the present invention is
generally a dendrite structure. Because of the effect of the
anisotropy of the structure, the mechanical properties of the Co
alloy are different depending on the directions (directions to the
layer direction). Concretely, the 0.2% proof stress and tensile
strength show higher values in the direction perpendicular to the
layered direction and the elongation shows a higher value in the
direction parallel to the layered direction. Consequently, it is
preferable to produce a biocompatible material while properly
adjusting the direction to which a load is mainly applied at the
time of use of the material and the layered direction, in
accordance with the use application of the biocompatible material.
Concretely, in the case of a use application in which the 0.2%
proof stress and tensile strength are mainly required, it is proper
to produce the Co alloy of the present invention by layered
manufacturing in a manner that the load direction at the time of
use of the biocompatible material and the layered direction are
perpendicular to each other. Also, in the case of a use application
in which elongation is mainly required, it is proper to produce the
Co alloy of the present invention by layered manufacturing in a
manner that the load direction at the time of use of the
biocompatible material and the layered direction are parallel to
each other.
[0035] This application claims the benefit of priority based on
Japanese Patent Application No. 2011-231703 filed on Oct. 21, 2011.
All the contents of Japanese Patent Application No. 2011-231703
filed on Oct. 21, 2011 are incorporated herein by reference.
EXAMPLES
[0036] Hereinafter, the present invention will be described more
concretely with reference to examples. The present invention is not
limited to the following examples and various modifications can be
appropriately made without departing from the gist of the invention
as defined above or hereinafter, all of which fall within the
technical scope of the present invention.
[0037] A molten Co alloy with the chemical composition described in
Table 1 was prepared and a Co alloy powder was produced by a water
atomization method. Thereafter, the powder was sieved to produce a
Co alloy powder with a particle diameter of not more than 45
.mu.m.
[0038] Each Co alloy in form of a dumbbell type tensile test
specimen according to JIS T6115, the dentistry casting
cobalt-chromium alloy, was produced from the above-mentioned powder
by a layered manufacturing apparatus (EOSINT M250 xtended) with the
laser output power and scan pitch (in plane direction) as described
in Table 1 (test Nos. 1 to 7, 9 and 11 to 15). Test Nos. 1 to 5, 9,
and 11 to 14 were layered-manufactured in a manner that the tensile
test direction and the layered direction were to be parallel to
each other and test Nos. 6, 7, and 15 were layered-manufactured in
a manner that the tensile test direction and the layered direction
were to be perpendicular to each other. The layered manufacturing
was carried out in an argon atmosphere, the irradiation diameter of
laser was 0.4mm (400 microns), and the layered thickness was 0.05
mm.
[0039] Each specimen was subjected to measurement of 0.2% proof
stress, tensile strength, and elongation (total elongation)
according to JIS T6115. The number of tests for each test No. was
3.
[0040] For comparison, Table 1 also shows the results of a specimen
(test No. 8) produced from Co-33 mass% Cr-5 mass % Mo-0.34 mass % N
satisfying the composition of the present invention by a
centrifugal casting method using a room temperature sand mold and a
specimen (test No. 10) produced from Co-29 mass% Cr-6 mass % Mo, a
material standardized as ASTM F75, by a centrifugal casting method
using a room temperature sand mold. In Table 1, in order to
describe that the samples were produced by the centrifugal casting
method, "As-Cast" is written in the column of laser output
power.
TABLE-US-00001 TABLE 1 Output power of 0.2% proof Tensile
Elongation Test Compositon of alloy laser Scan pitch.sup. 1 stress
strength El No. (mass %) (W) (mm) Tensile direction.sup. 2 (MPa)
(MPa) (%) 1 Co--33Cr--5Mo--0.34N 100 0.1 parallel 789 1017 15.9 2
150 0.1 parallel 760 1031 18.8 3 200 0.1 parallel 744 1040 22.4 4
200 0.2 parallel 814 1030 15.9 5 200 0.3 parallel 829 1050 16.7 6
200 0.1 perpendicular 900 1195 11.7 7 200 0.2 perpendicular 863
1123 8.6 8 As-Cast -- -- 606 910 14.2 9 Co--29Cr--6Mo 200 0.1
parallel 538 949 16.4 10 As-Cast -- -- 223 500 3.2 11
Co--33Cr--5Mo--0.41N 65 0.1 parallel 862 1117 21.8 12 98 0.1
parallel 845 1123 24.8 13 130 0.1 parallel 819 1120 26.2 14 130 0.2
parallel 856 1110 18.3 15 130 0.1 perpendicular 996 1328 13.2 .sup.
1It means the scan pitch in the plane direction. .sup. 2It measns
the tensile direction to the layered direction.
[0041] According to Table 1, all specimens of test Nos. 1 to 7 and
11 to 15, which are Co alloys of the present invention, were
excellent in mechanical properties of 0.2% proof stress, tensile
strength, and elongation. Further, from the results of these tests,
the effects on the mechanical properties given by the scan pitch
and the output power of the radial rays were made clear. FIG. 1 is
a graph illustrating a relationship between the scan pitch in the
plane direction and 0.2% proof stress, and FIG. 2 is a graph
illustrating a relationship between the output power of the radial
rays (output power of laser in the examples) and tensile strength
and elongation. According to FIG. 1 and FIG. 2, it can be
understood that the 0.2% proof stress is improved as the scan pitch
becomes wider and that the tensile strength and elongation are
improved as the output power of laser becomes higher.
[0042] Comparing test No. 3 with test No. 6, it can be understood
that elongation is excellent in the case where the tensile
direction is parallel to the layered direction and that the 0.2%
proof stress and tensile strength are excellent in the case where
the tensile direction is perpendicular to the layered direction.
The same tendency can be seen in the comparison of test No. 4 with
test No. 7 or of test No. 13 with test No. 15.
[0043] Further, FIG. 3 shows a photograph of a structure of the
specimen of test No. 3 observed by an optical microscope. FIG. 3(a)
is a photograph of a structure of a cross section perpendicular to
the layered direction, and FIG. 3(b) is a photograph of a structure
of a cross section parallel to the layered direction. According to
FIG. 3, it can be understood that a fine dendrite structure is
formed.
[0044] When the arm spacing of primary arms of the dendrite
structure for the test No. 3 was measured by measuring the number n
of times the dendrite interface crossed a certain reference length
L and carrying out calculation according to L/(n-1), it was 1.5
.mu.m. The arm spacings of primary arms of the dendrite structure
for the test Nos. 1, 2, 4 to 7, and 11 to 15 were all not more than
5 .mu.m, but the arm spacings of primary arms of the dendrite
structure for the test Nos. 8 and 10, which are out of the scope of
the present invention, exceeded 5 .mu.m because the specimens were
produced by a centrifugal casting method.
INDUSTRIAL APPLICABILITY
[0045] The Co--Cr--Mo alloy of the present invention can be used
suitably as an biocompatible material, for example, for dentistry,
orthopedics, and the like.
* * * * *