Nitrogen-containing sintered hard alloy

摘要

A nitrogen-containing sintered hard alloy includes a hard phase containing WC serving as an essential element and a carbide, nitride or a carbo-nitride of at least one transition metal being selected from the groups 4,A 5A and 6A of the periodic table or a composite carbo-nitride thereof and a binder phase containing Ni, Co and unavoidable impurities, an exudation layer containing a metal binder phase, mainly composed of Ni and Co, and WC being present on an alloy of this part, wherein the exudation layer is internally divided into a three layers in order of an outermost layer and an intermediate layer and an lowermost layer, wherein the outermost layer containing at least 0 percent by volume and not more than 30 percent by volume of WC with a rest being formed by a metal binder phase, the intermediate layer contains at least 50 percent by volume and not more than 100 percent by volume of WC with a rest being formed by a metal binder phase, the lower layer containing at least 0 percent by volume and not more than 30 percent by volume of WC with a rest being formed by a metal binder phase, wherein the outermost and lowermost layers being at least 0.1 mu m and not more than 10 mu m in thickness, the intermediate layer being at least 0.5 mu m and not more than 10 mu m in thickness. According to this composition, it is possible to provide a nitrogen-containing sintered hard alloy which can be employed as a cutting tool having high reliability with no surface coating also in working under conditions bringing a strong thermal shock. <IMAGE>