Microstructure and Mechanical Properties of Sintered Valve Seat Inserts for Automobiles with Cr Contents

摘要

Valve seat inserts are used in the valve train area of internal combustion engines. Good wear resistance is needed since repeated stress is applied by the valves under combustion gas atmosphere of high temperatures. Currently, most of the valve seat inserts are being manufactured by P/M route. In this study, the characteristics of materials especially the wear resistance with the addition of Cr-hard particles were investigated. The results of this study are as follows increase in the Cr-hard particles resulted in a decrease of the density of specimens. Pores formed by Cr diffusion from Cr-hard particles was attributed to the reduction in density. As a result, radial crushing strength was decreased with increase of the Cr-hard particals. Engine simulation test indicated that matrix can be hardened with the addition of Cr-hard particles. The excess addition of Cr-hard particles, however, degrades the wear resistance by the increase of residual pores. Therefore, the appropriate amount of Fe-Cr-C hard particles is 1 approx 5 wt percent.