退氮处理对SDHS2模具钢渗氮层组织与性能的影响

Effect of Denitriding on Property and Microstruture of Nitrided Case of SDHS2 Die Steel

采用光学显微镜和显微硬度仪对比研究了离子渗氮的SDHS2模具钢退氮处理前后渗氮层的组织和性能。结果表明:通过离子渗氮处理得到的渗层深度约230μm,渗层表面硬度达1 000 HV0. 3以上,渗层组织致密,与基体结合良好;分别经530和550℃退氮处理8、12、16 h后,渗氮层的硬度均大幅度降低。但随着渗氮时间的延长,渗层硬度随之提高;退氮温度的升高也会导致基体硬度的大幅度下降。综合比较得出,SDHS2模具钢退氮处理的最佳工艺为:退氮温度530℃、退氮时间8 h。在保证基体硬度满足要求的条件下,退氮处理可使表面硬度由处理前的1 000 HV0. 3以上降低至780 HV0. 3左右。

The microstructure and properties of nitrided layer of SDHS2 die steel before and after denitriding treatment were comparatively studied by optical microscope and microhardness tester.The result showed that the nitrided layer obtained by ion nitriding exhibited depth of about 230 μm,surface hardness more than 1 000 HV0. 3,and compact structure,and combined well to the base metal. After denitriding at 530 ℃ and 550 ℃ for 8 h,12 h,16 h respectively,the hardness of nitrided layer decreased significantly,however,with the extension of denitriding time,the hardness of nitrided layer increased. The increase of denitriding temperature also led to a significant decrease in matrix hardness. Taken together,the optimum nitriding treatment process for SDHS2 die steel was heating at 530 ℃ for 8 h. Under the condition that the hardness of the matrix meets the requirement,the surface hardness can be lowered from more than 1 000 HV0. 3 before denitriding to about780 HV0. 3 after denitriding.