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对球化退火后的5Cr8Mo2Si V刃具钢进行淬火和回火工艺的探究,用SEM和EDS对淬、回火后的显微形貌进行分析,用碳化物电解萃取和XRD分析等研究了5Cr8Mo2Si V刃具钢淬、回火过程中碳化物的析出行为,并用Jmat-Pro模拟回火过程中碳化物析出相的变化。结果表明:5Cr8Mo2Si V钢退火试样在1100℃淬火+520℃回火时有明显的二次硬化现象,球化退火组织中存在VC、Cr_(23)C_6、Cr_7C_3、Fe_3C、Si C和Mo_6C类碳化物。Mo_6C、Si C、Fe_3C、Cr_7C_3和Cr_(23)C_6型碳化物随着淬火温度升高依次溶入马氏体基体,最终只有VC分布在基体上。Mo_2C、VC、Cr_7C_3和Cr_(23)C_6型碳化物在回火过程中从马氏体中析出,且Mo_2C和VC型碳化物在520℃回火析出量出现峰值。结合Jmat-Pro模拟结果发现,5Cr Mo2Si V钢的二次硬化现象是残留奥氏体二次淬火和Mo_2C粒子的第二相强化共同导致,且Mo_2C粒子第二相强化效应符合位错切过机制。
The quenching and tempering process of 5Cr8Mo2Si V cutting tool steel after spheroidizing annealing was investigated. The microstructure of the steel after quenching and tempering was analyzed by SEM and EDS. Carbide precipitation behavior during quenching and tempering of the cutting tool steel and the change of precipitated phase of carbide during the tempering process by Jmat-Pro. The results show that there is obvious secondary hardening phenomenon when annealed at 1100 ℃ and tempering at 520 ℃ for 5Cr8Mo2Si V steel annealed samples. The existence of VC, Cr_ (23) C_6, Cr_7C_3, Fe_3C, SiC and Mo_6C carbide. Mo_6C, SiC, Fe_3C, Cr_7C_3 and Cr_ (23) C_6 carbides gradually dissolve into martensite matrix with the increase of quenching temperature, and finally only VC distributes on the matrix. The carbides of Mo_2C, VC, Cr_7C_3 and Cr_ (23) C_6 were precipitated from the martensite during the tempering process, and the amounts of Mo_2C and VC-type carbides precipitated at 520 ℃. Based on the Jmat-Pro simulation results, it is found that the secondary hardening phenomenon of 5Cr Mo2Si V steel is caused by the secondary austenite quenching and the second phase strengthening of Mo_2 C particles, and the second phase strengthening effect of Mo_2 C particles conforms to the dislocation cutting mechanism .