Hitachi Metals, Ltd.

Hitachi Carbide Tools, Inc.

Hitachi Tool Engineering, Ltd.

Hisaaki Ida

Yusuke Iyori

Katsuhiko Kojo

Nobuhiko Shima

Akibumi Negishi

A cermet alloy having a structure comprising a hard phase and a bonding phase, said hard phase comprising (1) at least one of MC, MN and MCN, wherein M is at least one element selected from Ti, Zr, Hf, Th, V, Nb, Ta, Pa, Cr, Mo, U and W and (2) at least one W-Co-B compound; said bonding phase comprising Co. The cermet has superior toughness and hardness, and can be worked by conventional sintering methods. The invention also includes a method for producing the cermet.

Cermet alloy and process for its production

This invention provides a cermet alloy improved in toughness high-temperature strength and chipping resistance. This cermet alloy consists essentially of 50-95% by weight of a hard phase of a composite carbo-nitride of at least both of W and Ti and, optionally, one or more elements selected from the group consisting of Groups 4a, 5a and 6a elements of the periodic table, the balance being a binding phase, of an Fe family element or elements and inevitable impurities, said composite carbo-nitride has a rim-and-core structure which comprises a core portion of a composite carbo-nitride poor in Ti and nitrogen, surrounded thereon by a rim portion of a composite carbo-nitride rich in Ti and nitrogen. It is preferred that the hard phase consists of 50% by volume or less of TiN or TiCN particles having N.gtoreq.C and forming no rim-and-core structure and the composite carbo-nitride having the rim-and-core structure.

Cermet alloy

A tough cermet made from 20-92 weight % of TiC and/or TiCN, 5-50 weight % of WC and 3-30 weight % of an iron-gorup metal. This tough cermet has a three phase grain microstructure and is made is mixing titanium carbonitride powder and up to 70 weight % of the total amount of the tungsten carbide fine powder. The resulting mixture is melted to form a solid solution, pulverized, mixed with the remaining amount of tungsten carbide fine powder, and sintered at temperatures of 1325.degree.-1650.degree. C.

Process for producing a tough cermet

A tough cermet made from 20-92 weight % of TiC and/or TiCN, 5-50 weight % of WC and 3-30 weight % of an iron-group metal. This tough cermet has a three phase grain microstructure consisting of a core phase rich in TiC and/or TiCN, an intermediate phase rich in WC and surrounding the core phase, and an outer phase made of (Ti,W)C and/or (Ti,W)CN and surrounding the intermediate phase. Because of this three-phase microstructure, the cermet has high toughness without sacrificing hardness. It is prepared by using WC powder of as fine as less than 3 .mu.m, without taking the course of forming a solid solution of TiC and/or TiCN and WC and pulverizing it.

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Kumagaya, Japan

Hisaaki Ida