METHOD FOR MANUFACTURING IRON-BASED SINTERED ALLOY VALVE SEAT WITH EXCELLENT WEAR RESISTANCE UNDER CONDITIONS OF HIGH SURFACE PRESSURE APPLICATION

摘要

PURPOSE: Provided is a valve seat that exhibits excellent wear resistance and displays little counterpart attack when utilized under conditions of high surface pressure application, thereby providing a valve seat that satisfies the demands associated with the increased size and output of internal combustion engines. CONSTITUTION: The method comprises a processes (a) in which an Fe-based alloy powder comprising 0.5 to 1.5 wt.% of C, 0.1 to 3 wt.% of Ni, 0.5 to 3 wt.% of Mo, 3 to 8 wt.% of Co, 0.2 to 3 wt.% of Cr and a balance of Fe and inevitable impurities and having an average particle diameter of 20-50 m is used as a raw material powder for forming matrix, and a Co-based alloy powder comprising 20 to 32 wt.% of Mo, 5 to 10 wt.% of Cr, 0.5 to 4 wt.% of Si and a balance of Co and inevitable impurities and having an average particle diameter of 20-50 m is used as a raw material powder for forming hard dispersed phase, a process (b) in which the Co alloy powder is blended and mixed with the Fe-based alloy powder so that it becomes 25-35 wt.% of the amount of sum totals of the Fe alloy powder and the Co alloy powder, and the press-formed body of a mixed powder is subjected to solid phase sintering in a vacuum atmosphere, and the Co, Cr, and Si components in the Co base alloy powder are diffusion migrated in a matrix, and at the same time an Fe component in the Fe-based alloy powder is diffusion migrated in a hard dispersed phase, respectively, and as a result, adhesiveness of the hard dispersed phase to the matrix is remarkably improved, and a process (c) in which the Fe-based sintered alloy product is infiltrated with molten copper or a copper alloy.