洁净燃料发动机粉末冶金阀座熔渗烧结工艺研究

采用正交试验优化了洁净燃料发动机粉末冶金阀座熔渗烧结工艺参数,分析了熔渗烧结工艺参数对阀座密度和上下面硬度等性能的影响。结果表明:随着渗铜量的增加,阀座材料密度迅速增加,上下表面硬度差距缩小。熔渗烧结温度对阀座材料密度影响不大。当熔渗烧结温度从1130℃升高到1165℃,材料硬度逐渐提高;当温度达到1200℃后,Co–Cr–Mo硬质颗粒中合金元素向基体中发生明显扩散,导致阀座硬度下降。熔渗烧结时间对材料密度影响不大,缩短时间有利于缩小上下面硬度差距。当渗铜质量分数达到20%,渗铜温度1165℃,渗铜时间40 min,阀座力学性能最佳。熔渗烧结后密度为8.15 g·cm~(-3),上下表面硬度分别为HRC 30.4和HRC 30.1,基体材料与Fe–Mo、Co–Cr–Mo硬质颗粒均有一定的冶金结合。

Study on melt infiltration sintering process of powder metallurgy valve seat for clean fuel engine

The melt infiltration sintering parametersof powder metallurgy valve seat for clean fuel engine were optimized by orthogonal experiment, the influences of melt infiltration sintering on the density and surface hardness of valve seat were studied. Results show that, the density of valve seat increases synchronously and the hardness difference between the upper and the lower surfaces decreases with the increase of copper infiltration content by mass. The sintering temperature has little effect on the density of valve seat. With the infiltration sintering temperature increasing from 1130℃ to 1165℃, the material hardness increases gradually. When the temperature reaches 1200℃, the alloying elements in Co-Cr-Mo hard particles present the obvious diffusion to the matrix, resulting in the decrease of valve seat hardness. The infiltration sintering time has little effect on the density of valve seat, shortening time is conducive to narrow the hardness difference between the upper and the lower surfaces. The optimized mechanical properties of valve seat are achieved, when the copper infiltration content by mass is 20％, the infiltration temperature is 1165℃, and the infiltration time is 40 min. At the same time, the density of productions after melt infiltration sintering are 8.15 g·cm-3, the upper and the lower surface hardness are HRC 30.4 and HRC 30.1, respectively, and the hard phase particles (Fe-Mo and Co-Cr-Mo) have the certain metallurgical bonding with matrix.