低温处理对3Cr2MoCoWV热作模具钢热疲劳性能的影响

INFLUENCE OF SUB-ZERO TREATMENT PROCESS ON THERMAL FATIGUE BEHAVIOR OF 3Cr2MoCoWV HOT WORKING DIE STEEL

通过比较低温处理前后3Cr2MoCoWV热作模具钢的热疲劳性能,结合透射电镜(TEM)分析低温处理对3Cr2MoCoWV钢热疲劳性能的影响。结果表明:贝氏体等温后,残余奥氏体呈薄膜状及块状两种分布形态。低温处理后,块状残余奥氏体完全转变为马氏体,贝氏体等温形成的残余奥氏体以更细小的膜状分布于贝氏体铁素体间。回火后,基体中超细小M2C型碳化物的弥散分布及少量未转变的残留奥氏体以薄膜状分布于贝氏体铁素体板条束间,提高材料的强度和韧性,阻碍了裂纹的萌生和扩展。低温处理得到材料的最佳强韧性配合,提高了3Cr2MoCoWV钢的热疲劳性能,其热疲劳损伤因子约是未经低温处理的一半。

The influence of sub-zero treatment on the thermal fatigue behavior of 3Cr2MoCoWV hot working die steel was investigated by means of transmission electron microscopy （TEM）. The results indicated that the retained austenite presented at the isothermal transformation temperature had two typical morphologies, film shaped and blocky morphologies. The sub-zero treatment impelled the blocky retained austenite to completely transform into martensite and impelled the film shaped retained austenite formed in isothermal bainitic processing to appear as thinner films between the lath bainite. Subsequently tempering, an amount of M2C carbides were uniformly distributed and a little film shaped retained austenite appeared as thin films between the lath bainite, which enhanced the strength and toughness, hindering crack initiation and propagation. The optimum combination of strength and toughness of the material was obtained by the sub-zero treatment, improving thermal fatigue resistance of 3CrMoCoWV steel. Thermal fatigue damage factor of 3Cr2MoCoWV subjected to the sub-zero treatment was approximately half of that of 3Cr2MoCoWV without such a treatment.