材料期刊网

采用OM，SEM，EDS，TEM以及力学性能试验，研究了热处理工艺对不同尺寸规格的粉末冶金高速钢W6Mo5Cr4V3Co8微观组织和力学性能的影响。结果表明，区别于普通高速钢，粉末冶金高速钢微观组织中没有大颗粒尺寸共晶碳化物，退火组织中碳化物均匀、细小，颗粒尺寸小于3μm。因此，不同尺寸规格钢材以及不同截面方向的组织都保持着高度的一致性；试验钢在1080～1180℃较宽的温度范围内淬火都能够获得67HRC以上的硬度。淬火后的组织为马氏体＋残留奥氏体＋未溶碳化物，淬火奥氏体晶粒尺寸非常细小；经过高温回火后，试验钢存在明显的二次硬化效应，二次硬化峰出现在520℃。二次硬化现象是由残留奥氏体转变和合金碳化物析出共同作用的结果，TEM分析显示，试验钢经高温回火析出的二次硬化碳化物包含VC；冲击韧性试验结果表明，不同截面尺寸粉末高速钢的冲击韧性基本相当，同一钢材其横向和纵向的冲击韧性相差不大。

Effect of heat treatment process on microstructure and mechanical properties of different size powder metallurgy (P/M) high speed steel W6Mo5Cr4V3Co8 were investigated by means of OM, SEM, EDS, TEM and mechanical property tests. Experimental results indicate that there is no large size eutectic carbides existence in the microstructure of the P/M high speed steel, which is different from conventional high speed steel. The carbides uniformly distribute in the annealed steel, and their sizes are all below 3 μm. Meanwhile, the uniform microstructure is observed for different size steel samples. The tested steel can obtain a high hardness level more than 67 HRC, when quenching in the temperature range of 1080 - 1180 ℃. The microstructure of the quenched steel consists of martensite, retained austenite and undissolved carbides. The grain size of quenched austenite is very fine. After high temperature tempering, the tested steel exhibits obvious secondary hardening effect after tempering at high temperature, and the secondary hardening peak appears at 520 ℃. The secondary hardening mechanism is the combination of the transformation of retained austenite and the carbide precipitation during tempering. The secondary hardening carbide VC is observed in the procipitation. Impact toughness test indicates that the similar impact toughness can be obtained for different size samples of the steel.