Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
2000-09-01
2003-03-04
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C051S307000, C051S309000, C427S307000, C427S309000, C427S331000, C428S216000, C428S457000, C428S408000, C428S698000, C428S701000
Reexamination Certificate
active
06528159
ABSTRACT:
TECHNICAL FIELD
The present invention relates to diamond sintered body tools and manufacturing methods thereof. More particularly, the present invention relates to a diamond sintered body tool having superior adhesion resistance, chipping resistance and strength as well as a manufacturing method thereof.
BACKGROUND ART
Since diamond sintered bodies have superior wear resistance and strength, they are widely used as tool materials in a field that requires strength and wear resistance such as the fields of cutting tools, drilling tools and wire drawn die tools. Such diamond sintered bodies are known, for example, as the one provided by filling diamond powder in a container made of a tungsten carbide—cobalt cemented carbide and sintering it at high temperature and under high pressure as described in Japanese Patent Publication No. 52-12126. Furthermore, Japanese Patent Laying-Open No. 54-114513 describes a diamond sintered body obtained by previously mixing diamond powder and iron group metal powder and maintaining the mixed powder at high temperature and under high pressure.
These diamond sintered bodies include an iron group metal such as cobalt as a sintering aid between sintered diamond particles.
As a diamond sintered body having improved heat resistance, the one in which an iron group metal is removed from the entire diamond sintered body is described in Japanese Patent Laying-Open Nos. 53-114589 and 7-156003.
However, when a conventional diamond sintered body including an iron group metal is used as a tool, cutting of a soft metal, especially an aluminum alloy, results in adhesion of the workpiece material on the cutting edge of the tool depending on the cutting conditions and thereby deteriorates the roughness of the finished surface of the workpiece material as well as the processing precision.
In a diamond sintered body from which an iron group metal is removed, the diamond sintered body includes a gap and has smaller strength, and therefore the diamond sintered body is easily chipped.
Therefore, the present invention was made to solve the above described problems, and its object is to provide a diamond sintered body tool capable of suppressing adhesion of a soft metal such as an aluminum alloy and having superior strength and chipping resistance.
SUMMARY OF THE INVENTION
The inventors conducted a study of adhesion of a workpiece material on the surface of a diamond sintered body tool when cutting an aluminum alloy. It was found out as a result that formation of a surface layer including at least one selected from silicon, a silicon oxide, a silicon carbide, a silicon nitride and a solid solution thereof on the surface of the diamond sintered body tool is remarkably effective for preventing adhesion of a workpiece material, which led to the present invention.
In other words, on the rake face or the flank face of a tool which is engaged in cutting, the diamond sintered body as a tool base material is in contact with the aluminum alloy and, under low cutting rate or dry cutting conditions, aluminum as a workpiece material adheres even on the surface of chemically stable diamond. This would be because the bond of aluminum and diamond on the surface of the diamond sintered body is relatively strong.
In contrast, if a surface layer including at least one selected from silicon (Si), a silicon oxide (SiO
2
), a silicon carbide (SiC), a silicon nitride (Si
3
N
4
) and a solid solution thereof is formed on the surface of the diamond sintered body tool, strongly bonded diamond and aluminum can be prevented from being in contact with each other and aluminum can be prevented from being adhered on the rake surface or the flank face of the tool because any of these surface layers are weakly bonded to aluminum.
Especially when the surface layer is formed of Si, SiO
2
, SiC or Si
3
N
4
, the bonding force of the surface layer and aluminum is lowered further since the surface layer is chemically stable, and the effect of preventing aluminum adhesion becomes higher.
The surface layer is generally formed in the following manner. When the surface layer is made of silicon, silicon powder having a particle size of at least 1 &mgr;m and at most 20 &mgr;m, for example, is pressed against the tool surface to form a thin silicon adsorption layer on the surface. When the surface is made of a silicon oxide, a silicon carbide and/or a silicon nitride, the surface layer is formed at a temperature of 400° C. to 500° C. using an arbitrary material gas selected from SiH
4
, O
2
, N
2
, C
2
H
4
by the plasma CVD (Chemical Vapor Deposition) method, for example. Besides, the surface layer can also be formed by using similar material gases and the methods such as the vacuum deposition, sputtering and ion plating.
Thus, in order to bring about the effect of adhesion prevention, the thickness of the surface layer formed on the diamond sintered body needs to be at least 0.1 nm. when the thickness of the surface layer exceeds 1 &mgr;m, formation of the surface layer often makes the surface rougher, which, on the contrary, easily causes adhesion of a workpiece material. Therefore, the thickness of the surface layer formed on the diamond sintered body is preferably in the range from 0.1 nm to 1 &mgr;m.
When an iron group metal such as Fe, Co and Ni is used as a sintering aid in the diamond sintered body, the iron group metal tends to be a starting point of adhesion caused at the cutting edge of the tool since a good wetting property is observed between such iron group metals and aluminum. Although the “wettability” generally means easiness of contact between a solid and a liquid, it refers to easiness of close contact between a tool and a workpiece in this specification. Thus, “a bad wettability” indicates a situation when a tool and a workpiece come into contact, they do not closely contact each other. On the other hand, “a good wettability” indicates a situation when a tool and a workpiece come into contact, they tend to closely contact each other.
By previously removing an iron group metal included in the diamond sintered body from the surface and thereafter forming the surface layer, adhesion is effectively prevented even when the surface of the diamond sintered body is partially exposed by long term cutting.
In short, a diamond sintered body including an iron group metal is used to manufacture a tool, and then the tool is immersed in an acid solution to remove the iron group metal from the surface of the diamond sintered body. Then, a surface layer including at least one selected from silicon, a silicon oxide, a silicon carbide, a silicon nitride and a solid solution thereof is formed on the tool rake surface or the tool flank face of the diamond sintered body tool. Thus, adhesion resistance for long term cutting can be improved.
Similarly, a diamond sintered body including an iron group metal is immersed in an acid solution to remove the iron group metal from the surface of the diamond sintered body. Thereafter, the diamond sintered body is used to form a tool. By forming a surface layer including at least one selected from silicon, a silicon oxide, a silicon carbide, a silicon nitride and a solid solution thereof on the tool rake surface or the tool flank face of the tool, adhesion resistance for long term cutting can be improved.
Furthermore, a diamond sintered body including an iron group metal is immersed in an acid solution to remove the iron group metal from the surface of the diamond sintered body. Thereafter, a surface layer including at least one selected from silicon, a silicon oxide, a silicon carbide, a silicon nitride and a solid solution thereof is formed on the surface of the diamond sintered body. By forming a tool using it, adhesion resistance for long term cutting can be improved.
Here, the diamond sintered body in which the iron group metal is removed from the surface as described above is characterized in that it includes an inner portion including a first content of the iron group metal, and a surface portion surrounding the inner portion and including a second content of the iron gr
Abe Makoto
Kanada Yasuyuki
Kuroda Yoshihiro
Nakai Tetsuo
Ogata Yasunobu
Fasse W. F.
Fasse W. G.
Sumitomo Electric Industries Ltd.
Turner Archene
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