激光表面淬火对铬钼铸铁组织和硬度的影响

Effect of laser hardening on microstructure and hardness of CrMo cast iron surface

采用TH-3DC3000型激光加工系统对铬钼铸铁进行了激光表面淬火处理,研究了不同激光功率和扫描速度对铬钼铸铁显微组织、表面硬度及硬化层深度的影响。结果表明,经激光表面淬火后,铬钼铸铁的组织由硬化区、过渡区和基体3个区域组成,硬化区组织为隐晶马氏体、残留奥氏体和球状石墨,过渡区组织为隐晶马氏体、珠光体和球状石墨,基体组织为铁素体、珠光体和球状石墨。在激光表面淬火未对试件产生过热影响时,激光功率的增大和扫描速度的降低均会提升铬钼铸铁的表面硬度和硬化层深度。在5 mm×20 mm的矩形激光光斑下,确定最优的参数组合为激光功率2300 W、扫描速度0.003 m/s,采用该参数组合对铬钼铸铁进行激光淬火处理时,表面硬度为760 HV0.3,硬化层平均硬度为724 HV0.3,硬化层深度可达1.4 mm以上。

TH-3 DC3000 laser processing system was used to laser hardening treatment on CrMo cast iron.The effects of different laser power and scanning speed on microstructure,surface hardness and hardened layer depth of CrMo cast iron were studied.The results show that after laser hardening,the microstructure of CrMo cast iron consists of three regions,which are hardened zone,transition zone and matrix.The microstructure of hardened zone is cryptocrystalline martensite,retained austenite and spherical graphite.The microstructure of transition zone is cryptocrystalline martensite,pearlite and spherical graphite.The microstructure of matrix is ferrite,pearlite and spherical graphite.When laser surface hardening does not have overheating effect on the test piece,the increase of laser power and the decrease of scanning speed will improve the surface hardness and hardened layer depth of the CrMo cast iron.Under the rectangular laser spot of 5 mm×20 mm,the optimal parameter combination is determined as laser power of 2300 W and scanning speed of 0.003 m/s.When this parameter combination is used for laser hardening of the CrMo cast iron,the surface hardness is 760 HV0.3,the average hardness of the hardened layer is 724 HV0.3,and the depth of hardened layer is more than 1.4 mm.