激光相变硬化对轴承钢组织与性能的影响研究

本文对低温回火态Gcr15轴承钢的激光相变硬化处理进行了研究.试验了激光处理的工艺参数对硬化过程的显微组织、淬硬层的硬度变化、残余应力分布、残留奥氏体形貌与数量以及耐磨性能等的影响.结果表明:经激光相变硬化处理后,Gcr15钢的表面硬度可达HV1000以上,硬化层的显微组织为缺陷密度高的隐针马氏体,晶粒度为ASTM 14级,残留奥氏体约达20%,呈膜态分布于马氏体条片之间及碳化物周围,超细的碳化物非常弥散地分布着,表面层保持较大的压应力而耐磨性能明显提高.据此,可以认为激光相变硬化的强韧化机制是:晶粒细化强化、亚结构强化,弥散析出强化以及残留奥氏体强化等的综合贡献.

A Study of the Effect of Structures and Mechanical Properties by Laser Transformation Hardening of Bearing Steel

Laser transformation hardening of Ger 15 bearing steel at low tem-perature tempering condition is studied.Experimental work were carried outto determine the effect of technical parameters of laser treatment on the micro-structures,change of hardness in the hardened layer,distribution of residualstress,quantities of retained austenite and wear resistance The results demon-strated that the surface hardness of Gcrl5 steel through laser hardeningattained as high as above Hv 1000.The microstructures were oryptocrystallinemartensite with a high density of dislocation,whose grain size was ASTM14~#.The retained austenite was about 20% with film-like distribution withinthe plates of martensite or round the carbides.Ultra-fine grains were scatter-ingly distributed,rather high compressive residual stresses were measured inthe surface region and the wear resistance was enhanced significantly.Basedon these results,it is supposed that the strengthening and toughening mecha-nism from laser transformation hardening is the combined merits of grain refi-nement strengthening,substructure strengthening,precipitation hardening andretained austenite strengthening.