Production method of iron base sintered alloy valve seat

Abstract

A valve seat is produced by (a) using, as a raw material powder for forming a matrix, an Fe-based alloy powder with an average particle size of 20 to 50 mum, and using, as a raw material powder for forming a hard dispersion phase, a Co-based alloy powder with an average particle size of 20 to 50 mum, (b) conducting solid phase sintering, under vacuum, of a pressed compact formed from a mixed powder generated by mixing the Co-based alloy powder into the Fe-based alloy powder in sufficient quantity to account for 25 to 35% by weight of the combined weight with the Fe-based alloy powder, and causing the Co, Cr and Si components of the Co-based alloy powder to diffuse and migrate into the matrix, and the Fe component of the Fe-based alloy powder to diffuse and migrate concurrently into the hard dispersion phase, thereby markedly improving adhesion of the hard dispersion phase to the matrix, and forming, as a result, an Fe-based sintered alloy substrate with a porosity of 10 to 20%, and comprising an Fe-Co alloy matrix in which is uniformly distributed a hard dispersion phase of a Mo-Fe-Co alloy having a 2 phase mixed system of an Fe-Co alloy phase and a Mo-Co alloy phase, and (c) infiltrating this Fe-based sintered alloy substrate with copper or a copper alloy.

Description

technical field [0001] The present invention relates to a valve seat belonging to a structural part of an internal combustion engine such as a diesel engine or a gasoline engine. In particular, the present invention relates to a valve seat of an iron-based sintered alloy having excellent wear resistance in high surface pressure applications (hereinafter simply referred to as a valve seat) seat). Background technique [0002] The cylinder heads of internal combustion engines such as diesel or gasoline engines have valve seats that serve as exhaust and intake valves. [0003] Generally, the valve seat is usually made of iron-based sintered alloy with the following composition, expressed in weight percentage (all % values ​​below refer to weight percent composition%): [0004] C: 0.7-1.4%, [0005] Si: 0.2-0.9%, [0006] Co: 15.1-26%, [0007] Mo: 6.1-11%, [0008] Cr: 2.6-4.7%, [0009] Ni: 0.5-1.2%, [0010] Nb: 0.2-0.7%, [0011] and the balance being Fe and unavoida...

AI Technical Summary

Problems solved by technology

Therefore, the seat load on the valve contact surface of the valve seat is increased even more, which means that the valve seat will inevitably work under high surface pressure conditions, but when the conventional valve seat as described above or other When any kind of valve seat is used under the condition of high surface pressure, the wear of the valve seat will be accelerated relatively quickly, which means that the valve seat will reach the limit of service life in a short period of time