Importance

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Abstract

The invention enables to obtain a compound sintered compact for use in a cutting tool having particularly high properties in respect of bonded strength, hardness, wear resistance, plastic deformability and rigidity by bonding a diamond or cubic boron nitride containing hard layer to a cemented carbide substrate with interposition of an intermediate bonding layer. A powder for forming the intermediate bonding layer comprising cubic boron nitride in an amount less than 70 volume %, the residual part principally consisting of a compound selected from among carbides, nitrides, carbonitrides or borides of 4a, 5a, 6a transition metals of the periodic table, an admixture thereof, or a mutual solid solution compound thereof, after pressing or in the state of powder, is placed on the cemented carbide substrate to a thickness less than 2 mm, or preliminarily applied to said cemented carbide substrate, further on said powder being placed a powder for forming the hard sintered compact containing diamond or cubic boron nitride in an amount in excess of 20 volume % after pressing or in the state of powder, the whole being hot pressed under an ultrahigh pressure and a high temperature to sinter the diamond or cubic boron nitride containing hard layer and the intermediate layer as well as to bond said hard layer, intermediate layer and substrate to each other, thereby enabling to obtain a compound sintered compact having the aforesaid superior properties for use in a cutting tool.

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First Claim