Compositions: ceramic – Ceramic compositions – Refractory
Patent
1998-07-16
1999-12-28
Group, Karl
Compositions: ceramic
Ceramic compositions
Refractory
501 961, 501 963, 501 966, C04B 355831, C04B 355835
Patent
active
060081538
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a high-pressure phase boron nitride-based sintered body, and more particularly, it relates to a high-pressure phase boron nitride-based sintered body for a cutting tool, which is improved in wear resistance and chipping resistance.
BACKGROUND TECHNIQUE
High-pressure phase boron nitride represented by cubic boron nitride (hereinafter referred to as cBN) is the next high-hardness material to diamond, and its reactivity with a ferrous material is low as compared with diamond, and hence cBN-based sintered bodies are used for various cutting tools.
Further, a material which is of high hardness and high strength is earnestly desired not only in a cutting application but also in various applications such as a wear-resistant part provided on a sliding part and a shock-resistant part employed for a defensive wall, for example. In a conventional high-pressure phase boron nitride-based sintered body, however, there has been a problem in compatibility of hardness and strength, and no sufficient performance has been attained.
At this point, cBN is a typical non-sinterable material ranking with diamond, and is a high-pressure stable phase. Therefore, extreme sintering conditions of 2000.degree. C. and at least 8 GPa are required, in order to sinter cBN grains. Therefore, cBN grains cannot be bonded to each other under industrial sintering conditions of 1450.degree. C. and not more than 4.5 GPa. Therefore, it is necessary to sinter cBN powder and binder powder after mixing, in order to prepare a cBN-based sintered body under industrial sintering conditions. Powder of Al, Ti Al, Ti Al.sub.3, TiN or TiC is employed as this binder powder. And, cBN-based sintered bodies industrially produced by employing a binder (hereinafter referred to as an Al-based binder) consisting of an Al metal or an intermetallic compound of at least one of Al elements can be roughly classified into the following two types:
It is disclosed in Japanese Patent Laying-Open Gazette No. 55-126581 that a cBN-based sintered body (A) consisting of at least 80 weight % of cBN and a binder phase is obtained by performing sintering while employing cBN grains and Al as starting materials. This is because metallic Al or an intermetallic compound of Al such as Ti Al.sub.3 causes fused Al in a high-temperature state in sintering and promotes formation of neck growth between the cBN grains. At this point, neck growth indicates such a state that the cBN grains are fused or bonded and a continuous mosaic or an alternate material is generated. A cBN-based sintered body having a cBN content of 85 to 90 volume % is worked into a product in practice. The transverse rupture strength of this cBN-based sintered body is about 80 to 100 kgf/mm.sup.2 under a condition of a 4 mm span with a test piece of 6 mm in length, 3 mm in width and 0.4 to 0.45 mm in thickness.
On the other hand, a cBN-based sintered body (B) consisting of about 50 to 80 volume % of cBN and a binder phase is obtained by performing sintering while employing cBN grains, an Al-based binder and a nitride or a carbide of an element of the group 4a, 5a or 6a of the periodic table represented by TiN and TiC and the like or a solid solution thereof (hereinafter referred to as a transition metal nitride or the like) as starting materials. This is because metallic Al or an intermetallic compound of Al such as TiAl.sub.3 causes fused Al in a high-temperature state in sintering, forms reaction products between the cBN grains and grains of the transition metal nitride or the like and between the grains of the transition metal nitride or the like, and forms strong binding. A cBN-based sintered body having a cBN content of about 50 to 80 volume % is worked into a product in practice, as a high-strength cutting tool employed for an intermittent cutting application or the like. The transverse rupture strength of this cBN-based sintered body is about 90 to 110 kgf/mm.sup.2 under a condition of a 4 mm span with a test piece for measurement of 6 mm in length, 3 mm in width
REFERENCES:
patent: 4666466 (1987-05-01), Wilson
patent: 5328875 (1994-07-01), Ueda et al.
patent: 5466642 (1995-11-01), Tajima et al.
patent: 5569862 (1996-10-01), Kuroyama et al.
patent: 5925585 (1999-07-01), Schoennahl et al.
Fukaya Tomohiro
Kukino Satoru
Nakai Tetsuo
Shiraishi Junichi
Uesaka Shinya
Fasse W. F.
Fasse W. G.
Group Karl
Sumitomo Electric Industries Ltd.
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