摘要
本文借助光学显微镜,扫描电镜,透射电镜分析了 HT200灰铸铁经激光处理后硬化带中显微组织特征,并进行快速滑动磨损试验,探讨显微组织和耐磨性的关系。实验结果表明:HT200经激光熔化处理后表层显微组织为树枝(M+A′)+树枝间莱氏体(M+A′+Fe_3C);经激光不熔化处理后表层显微组织为马氏体针团+A′+G。激光处理后耐磨性显著提高。HT200经激光熔化处理后其磨损经历塑性变形—萌生显微裂纹—裂纹扩展—断裂;而经不熔化处理后其磨损经历裂纹扩展一断裂。HT200经激光处理后表面形成变态莱氏体、消除或减少石墨、细化显微组织、增加残余奥氏体量对提高耐磨性有利。
The microstructures of laser-hardened layer on the gray cast iron HT200 were examined by optical microscopy,scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The wear lest wasdone in a sliding wear device.The relation between microstrueture andwear resistance was studied.It is indicated that depending on the beanscanning speed,two basic kinds of microstructure can be produced in thelaser hardened layer—a dendritic structure with dendritic(M+A′)and int-erdendritic transformed ledeburite(M+A′+Fe_3C)for laser melting process-ing and a microstructure with cluster of martensite,retained austenile andgraphite(M+A′+G)for non-melting processing.Gray cast iron showsmarked improvement in wear resistance after laser processing.The wearprocedure is the plastic deformation—initiation of microcrack—growth ofcrack-fracture for laser melting processing and the growth of crack-fracturefor laser non-melting processing.Formation of transformed ledeburite,eli-minating or decreasing graphic flakes,refining microstructure and increas-ing retained austenite are beneficial to the improvement in wear resistanceafter laser processing.
