热处理对高Co、高V粉末高速钢PM60碳化物析出的影响

Effect of heat treatment process on carbide precipitation in high Co and high V high-speed steel PM60

PM60高速钢是通过粉末冶金方法制备,与普通高速钢相比,含有大量的Co元素,可以促进二次碳化物的析出。PM60高速钢在1120、1150、1180和1210℃淬火并油冷,然后在540、560和580℃分别进行3次回火。热处理结束之后,通过金相显微镜、扫描电镜、洛氏硬度计对热处理后PM60高速钢显微组织、析出相和硬度进行分析,结合JMatpro热力学计算软件研究淬火和回火热处理前后样品中碳化物的种类、形貌、成分、分布以及析出行为。结果表明,原来的析出相为MC、M6C、M23C6和M7C3相,经热处理后为MC和M6C相。经过能谱分析发现,这两种类型的碳化物,一类是颜色较暗的富V类碳化物,另一类是颜色较亮的富W、Mo类碳化物。淬火过程中部分碳化物溶解,回火过程中有细小弥散分布二次碳化物析出。在1180℃淬火+540℃回火条件下,材料硬度最高。

Compared with ordinary high speed steels,PM60 high-speed steel prepared by powder metallurgy contains a large amount of Co element,which can promote the precipitation of secondary carbides.The PM60 high-speed steel was quenched at 1120,1150,1180 and 1210℃,and oil cooling,and then tempered three times at 540,560 and 580℃.After the heat treatment,the microstructure,precipitated phases,and hardness of the PM60 high speed steel after heat treatment were analyzed by metallographic microscope,scanning electron microscope,and Rockwell hardness tester.The types,morphology,composition,distribution,and precipitation behavior of the carbides in the samples before and after heat treatment were investigated by using JMatPro thermodynamic calculation software.The results show that the original precipitation phases are MC,M_6C,M_(23)C_(6)and M_7C_3 phases,after heat treatment,the precipitation phases are MC and M_6C phases.By energy spectrum analysis,two types of carbides are found:the dark V-rich carbides,and the bright W and Mo-rich carbides.In the quenching process,part of the carbides is dissolved,and in the tempering process,there is fine dispersive secondary carbides precipitated out.Under the condition of quenching at 1180℃+tempering at 540℃,the hardness of the tested steel is the highest.