SURFACE HEAT-TREATED SINTERED ALLOY, ITS MANUFACTURE AND COATED SURFACE HEAT-TREATED SINTERED ALLOY WITH HARD FILM

摘要

PURPOSE:To manufacture a surface heat-treated sintered metal having excellent chipping resistance in a sintered alloy constituted of a hard phase such as the carbide of the metals in the group 4a of the periodic table and a bonding phase of the iron metals by specifying the concn. distribution in the bonding phase on the surface. CONSTITUTION:A sintered alloy constituted of a hard phase contg. at least one kind among the carbide, carbon nitride, carbon oxide, carbon nitrogen oxide or their mutual solid solution of the metals in the group 4a, 5a and 6a (such as Ti, V and Cr) in the periodic table and a bonding phase contg. at least one kind among the iron metals is prepd. After the sintering or in the sintering stage, the surface of the sintered alloy is subjected to decarbonization treatment at the temp. in the area of solid-liquid coexisting temp. of the bonding phase at a slow speed, and the relative concn. of the bonding phase in the sintered alloy is regulated in such a manner that the maximum value is shown on the surface of the sintered alloy and the value is reduced toward the inner part from the surface to at least 5mu. By this method, the surface heat-treated sintered alloy having excellent chipping resistance can be obtd.