Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1993-01-25
1995-06-06
Mai, Ngoclan T.
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
75240, 75242, 419 14, 419 18, 419 23, 419 38, 419 49, 419 53, 419 54, C22C 2902, B22F 314
Patent
active
054218527
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a hard alloy with high hardness, high abrasion resistance, high corrosion resistance, non-magnetism and high rigidity, which has excellent performance for nozzles for high pressure water flow and for tools for cutting, sliding and drawing die.
PRIOR ART
For obtaining a hard alloy with high hardness, high abrasion resistance, high corrosion resistance, non-magnetism and high rigidity, which has excellent performance when used for a nozzle for high pressure water flow and for tools for cutting, sliding and drawing die, there have conventionally been available such improved ceramics as silicon carbide, silicon nitride and boron carbide. These ceramics may be obtained by pressing a powder of raw material into a finally desired shape and then sintering.
On the other hand, it has been known that hard alloys for making tools with fair abrasion resistance and excellent cutting performance are obtained from a hard phase consisting of carbides, nitrides and others of metal elements in the IVa, Va and VIa families and a binding phase of iron family metals. In particular, WC--Co type cemented carbides are most excellent in mechanical properties, and so they are useful in the fields of cutting tools and abrasion-resistant tools. A WC--Co type cemented carbides is obtained by drying and granulating a mixture of WC powder (hard phase) and Co powder (binding phase) and then pressing and sintering the product.
However, since ceramics are truly high in hardness but low in toughness, it is difficult to apply them to fields where mechanical impacts are frequent. It is also known that cemented carbides made of a hard phase of carbides and nitrides of metal elements in the IVa, Va and VIa families and a binding phase of iron family metals have limited hardness. This is because decreasing the amount of the binding phase for the sake of increasing hardness of the alloy lowers its toughness. Particularly when the amount of the binding phase in the alloy is less than 2% by weight, uniform dispersion of the binding phase over the surface of the hard phase of WC particles becomes very difficult with the result of extensive decrease of the toughness. In the ordinary cemented carbides the binding phase made of Co and other metals cannot be decreased to less than 2% by weight.
The assignee of the present invention previously filed Japanese Patent Application No. 250437/1991, which discloses that specified amounts of Mo.sub.2 C and VC are added to a WC--Co mixture to prevent the wettability of WC--Co from being inhibited upon decreasing the amount of Co, and that selection of the particle size of WC and making conditions of sintering or HIPping optimum for the material in the employed amount of the binding phase make it possible to obtain a hard alloy composed of WC--Mo.sub.2 C--VC--Co with a small amount of the binding phase.
However, even in the above described hard alloy whose composition is 4 phases of WC--Mo.sub.2 C--VC--Co, as far as Co is present as a metal in the alloy playing a role of ordinary binding phase, there still exist limitations in the hardness and toughness similar to previous alloys. In addition, since there are considerable differences in such properties as the Young's modulus and hardness between the hard and binding phases, a large stress tends to exist at the interface impairing the toughness of the alloy.
DISCLOSURE OF THE INVENTION
Thus, a first objective of the present invention is to provide a hard alloy in which the hardness of the alloy is increased more than ever by using a small amount of the binding phase and yet lowering the toughness of the alloy is prevented.
A second objective of the present invention is to provide a cemented carbide with high density and high strength, in which the wettability of the hard phase containing WC as the major component and the binding phase is improved.
A third objective of the present invention is to provide a method of manufacturing the above cemented carbide with high density and high strength.
BRIEF DES
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Maruyama Masao
Nakagaki Hiroshi
Shirane Minori
Mai Ngoclan T.
Sumitomo Electric Industries Ltd.
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