Compositions: ceramic – Ceramic compositions – Carbide or oxycarbide containing
Reexamination Certificate
1997-06-19
2001-01-09
Silbaugh, Jan H. (Department: 1732)
Compositions: ceramic
Ceramic compositions
Carbide or oxycarbide containing
C501S096100, C501S096300, C501S102000, C419S012000, C419S015000
Reexamination Certificate
active
06171989
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a silver-colored sintered product used for ornamental articles, tools, sliding members, blades for industrial use, stamps, spectacle frames, tablewares, and sporting goods such as pins of shoes, golf clubs, etc. and to a method of producing the same. In particular, the invention relates to a silver-colored sintered product having large strength, high hardness, resistance against chipping, excellent resistance against corrosion and excellent ornamental property that can be used as ornamental materials such as frames for timepieces, necktie pins, bracelets, pierced earrings, earrings, and fishing goods, and to a method of producing the same.
2. Description of the Prior Art
Ornamental parts such as armoring parts for timepieces and the like must have good corrosion resistance, increased resistance against scratching, and long-lasting metallic luster. As materials having metallic luster that are best suited for use as ornamental parts, there have been used a stainless steel and carbides of metals such as sintered alloys obtained by bonding WC and TiC with such metals as Ni and Co.
The stainless steel has an excellent corrosion resistance but has a low hardness and is subject to be scratched. The sintered alloys comprising chiefly WC and TiC and bonded with metal elements such as Ni and Co, have no problem in regard to the hardness but have a low corrosion resistance against the human sweat and sea water.
In recent years, TiB
2
sintered products which are borides of titanium having high hardness and excellent corrosion resistance have been developed and placed in practical use (see, for example, Japanese Laid-Open Patent Publication No. 27975/1983, Japanese Patent Publication No. 18458/1984, Japanese Laid-Open Patent Publications Nos. 270265/1986 and 294739/1993).
These TiB
2
sintered products have a flexural strength of from 800 to 1000 MPa, Vickers' hardness of from 18 to 24 GPa, fracture toughness of from 4 to 7 MPa·m
½
and excellent corrosion strength.
However, the above-mentioned TiB
2
sintered products must be sintered at a temperature of as high as from 1600 to 2000° C.; i.e., sinterability is poor.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a silver-colored sintered product having excellent properties such as hardness, corrosion resistance, etc. which are comparable with those of the TiB
2
sintered product, and can be sintered at a temperature of as low as from 1300 to 1600° C., and a method of producing the same.
Another object of the present invention is to provide a silver-colored sintered product for ornamental parts, which, when it is used as an ornamental article, does not cause the user to develop metal allergy.
According to the present invention, there is provided a silver-colored sintered product containing at least titanium, carbon and boron as constituent elements and having excellent corrosion resistance, a flexural strength of not smaller than 700 MPa, a Vickers' hardness of not smaller 9.0 GPa and a fracture toughness of not smaller than 5.0 MPa·m
½
, the sintered product including in the composition thereof a metal boride phase represented by the following composition formula (I) and a metal carbide phase represented by the following composition formula (II),
(Ti
a
M
b
)B
c
, (I)
(Ti
x
N
y
)C
z
(II)
wherein M and N denote, respectively, at least one of the elements selected from the elements of the Groups 4a, 5a and 6a of periodic table but excluding Ti, and
a, b, c, x, y and z satisfy the following relations:
0.8≦a≦1.0
0≦b≦0.2
0.8≦c≦1.0
a+b=1
0.8≦x≦1.0
0≦y≦0.2
0.6≦z≦1.0
x+y=1
According to an embodiment of the present invention, there is provided a silver-colored sintered product comprising, as metal element components, a boride phase composed chiefly of titanium, a carbide phase composed chiefly of titanium, and the remainder being a metal phase composed chiefly of titanium and unavoidable impurities, wherein when the composition formulas of said boride and said carbide based upon their atomic ratios are expressed as,
(Ti
a
M
b
)B
c
,
(Ti
x
N
y
)C
z
wherein M and N denote, respectively, at least one of the elements selected from the elements of the Groups 4a, 5a and 6a of periodic table but excluding Ti,
a, b, c, x, y and z satisfy the following relations:
0.8≦a≦1.0
0≦b≦0.2
0.8≦c≦1.0
a+b=1
0.8≦x≦1.0
0≦y≦0.2
0.6≦z≦1.0
x+y=1
The sintered product of this embodiment has excellent strength, hardness, resistance against chipping, corrosion resistance, favorable sinterability, and exhibits silver-colored mirror plane.
According to a second embodiment of the present invention, there is provided a silver-colored sintered product comprising titanium in an amount of from 80 to 95% by weight, boron in an amount of from 3 to 12% by weight and carbon in an amount of from 2 to 8% by weight per the whole amount of titanium, carbon and boron which are the constituent elements, the sintered product including a TiC phase and a TiB phase together, as well as a silver-colored sintered product containing elements of the Groups 4a, 5a and 6a of periodic table but excluding Ti in amounts of from 0.5 to 20.0 parts by weight per 100 parts by weight of the three chief components of from 80 to 95% by weight of titanium, from 3 to 12% by weight of boron and from 2 to 8% by weight of carbon, said sintered product including a TiC phase and a TiB phase together.
These sintered products, too, have excellent strength, hardness, resistance against chipping, corrosion resistance and sinterability.
According to the present invention, furthermore, there is provided a silver-colored sintered product of the above-mentioned second embodiment wherein the contents of metals that may serve as a cause of allergy are suppressed to be not larger than 0.3% by weight per the whole amount of the sintered product.
The sintered product has excellent strength, hardness, resistance against chipping, corrosion resistance and sinterability as described above. Moreover, even when ornamental articles made of this sintered product are worn by men, they do not become a cause of allergy to men.
According to the present invention, there is further provided a method of producing a silver-colored sintered product by molding a mixture of a powder of titanium, a powder of a carbide of titanium and a powder of a boride of titanium, into an article of a predetermined shape, and firing the molded article in a non-oxidizing atmosphere at a temperature of from 1300 to 1600° C.
REFERENCES:
patent: 2084349 (1937-06-01), Laise
patent: 2581252 (1952-01-01), Goetzel et al.
patent: 3380856 (1968-04-01), Pohl
patent: 3669695 (1972-06-01), Iler et al.
patent: 4731115 (1988-03-01), Abkowitz et al.
patent: 4968348 (1990-11-01), Abkowitz et al.
patent: 5256368 (1993-10-01), Oden et al.
patent: 5403790 (1995-04-01), Claar et al.
patent: 5641921 (1997-06-01), Dennis et al.
patent: 58-27975 (1983-02-01), None
patent: 59-18458 (1984-04-01), None
patent: 61-270265 (1986-11-01), None
patent: 5-294739 (1993-11-01), None
Hogan & Hartson LLP
Jones Kenneth M.
Kyocera Corporation
Silbaugh Jan H.
LandOfFree
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