硬质颗粒增强型新能源汽车铁基粉末冶金阀座的热处理工艺

Heat treatment process of rigid particle reinforced iron-based powder metallurgy valve seat for new energy vehicle

以W6Mo5Cr4V2高速钢粉末为基体粉末,添加Fe-Mo、Co-Cr-Mo等硬质颗粒,压制成阀座坯体,然后以专用渗铜粉(Cu-Fe-Mn)作为熔渗剂,通过真空高温熔渗制备颗粒增强铁基粉末冶金阀座,进行淬火和回火热处理,研究淬火温度与回火温度对阀座材料基体与硬质颗粒显微硬度以及阀座材料摩擦磨损性能的影响,并通过正交试验优化材料的热处理工艺。结果表明:淬火温度对阀座材料的W6Mo5Cr4V2基体和Fe-Mo、Co-Cr-Mo硬质颗粒硬度和耐磨性能影响较大,在1 140~1 260℃温度下淬火时,Fe-Mo和Co-Cr-Mo硬质颗粒发生明显扩散。淬火对铜覆盖区域的碳化物影响较小,覆盖区域内未溶碳化物较多且尺寸较大。淬火温度为1 220℃时,材料基体以及Fe-Mo和Co-Cr-Mo硬质颗粒的显微硬度(HV)分别为528,892和632。回火温度对阀座的硬度影响小,回火温度为520℃时阀座硬度最高。在淬火温度为1 220℃,回火温度5 20℃,回火次数为3次的条件下,阀座的硬度(HRC)达到49.2,磨损量为0.029 5 g。

The valve seat frame body was pressed using W6Mo5Cr4V2 as based powder and adding Fe-Mo, Co-Cr-Mo and other hard particles. The particle reinforced iron-based powder metallurgy valve seat was prepared by vacuum high temperature infiltration method using special copper powder （Cu-Fe-Mn） as infiltration agent, with quenching and tempering heat treatment. The effects of quenching temperature and tempering temperature on the micro hardness of valve seat matrix and particles and the friction and wear properties of the valve seat materials were studied. The orthogonal treatment was used to optimize the heat treatment process. The results show that the quenching temperature has a great influence on the hardness and wear resistance of the valve seat material matrix W6Mo5Cr4V2, Fe-Mo and Co-Cr-Mo hard particles. When quenching at 1 140？1 260 ℃, Fe-Mo and Co-Cr-Mo hard particles diffuse obviously. The effect of quenching on carbides in copper-covered areas is small. There are more undissolved and larger size carbides in the covering area. When the quenching temperature is 1 220 ℃, the microhardness （HV） of the matrix material, Fe-Mo and Co-Cr-Mo hard particles are 528, 892 and 632 respectively. Tempering temperature has little effect on hardness of the valve seat. The highest hardness can be obtained when the tempering temperature is 520 ℃. The seat with hardness （HRC） of 49.2 and wear quantity of 0.029 5 g are obtained at quenching temperature of 1 220 ℃, tempering temperature of 520 ℃ and tempering number of 3.