This paper studies the laser transformation hardening of 42CrMo steel at low temperature tempering condition,and carries out experiments on the effect of technical parameters of laser treatment on the microstructures,on the depth of laser hardening,and on the change of hardness in the hardening layer and wearing resistance. The results from experiments show that the microh}rdness of laser hardened zone may be as high as Hv1150. The microstruc tures are mainly oryptocrystalline martensite with a high density of dislocation. Its microhardness can be doubled,and its wearing resistance can be increased by four times or so. At the end,the paper discusses the mechanism of laser transformation hardening.
