H13 Steel Surface Laser Cladding Modification

In order to improve the wear resistance of H13 steel,the laser claddings of H13 steel substrate with NiCrBSi,NiCrBSi+Ti,NiCrBSi+Ti+C and NiCrBSi+TiC were performed.The macroscopic qualities of all kinds of the coatings were analysed and compared,and the process parameters of laser cladding and the materials of coatings were optimized.The microstructure of the laser coatings was characterized by XRD and SEM.The microhardness of the coatings was examined and contrasted using HXD-1000 microhardness tester.The wear properties were examined using M-200 wear test machine.The results show that the clad materials and the process parameters are the important factors to influent the quality of laser cladding.In the condition of optimized process parameters,we can obtain the smooth and continuous laser claddings of NiCrBSi and NiCrBSi+Ti+C.The miscrostructure analyses show that three regions with different microstructures exist in the surface of coatings:the clad layer,the binding zone of the clad layer with the substrate,and the heat-affected zone in the substrate.The clad layer of NiCrBSi coatings on H13 alloy substrate consists of the phases ofγ-Ni,Cr₇C₃ and CrB.The clad layer of NiCrBSi+Ti coatings on H13 alloy substrate consists of the phases ofγ-Ni,compound of Cr and Ni with Ti.The clad layer of NiCrBSi+Ti+C coatings on H13 alloy substrate consists of the phases ofγ-Ni,Cr₇C₃ and the in-situ synthesized TiC.The clad layer of NiCrBSi+TiC coatings on H13 alloy substrate consists of the phases ofγ-Ni,Cr₇C₃ and the undissolved TiC and the precipitated TiC distributed dispersively.The hardness profiles of all the coatings obey the same law.The hardness is decresed from the clad layer to the heat-affected zone.The hardness of the clad layer of NiCrBSi+Ti+C coatings reaches HV850,which is improved by near three times compared with the substrate H13 steel.The hardness of the clad layer of NiCrBSi coatings reaches HV700,which is improved by above twice compared with the substrate H13 steel.The tribological properties on M-200 wear test machine show that the wear volume of the NiCrBSi coating is 1/10 of the H13 steel,the wear volume of the NiCrBSi+Ti+C coating is 1/15 of the H13 steel.The wear resistance of the NiCrBSi+Ti+C coating is better in the strict conditions.The wear mechanism of the NiCrBSi clad layer is a mixture of oxidation wear and grain abrasion.The wear of NiCrBSi+Ti+C clad layer is the abrasion,which is caused by the peeling-off TiC particles from the clad layer.The NiCrBSi+Ti+C clad layer which obtains the good wear resistance and microhardness could be strengthened by several mechanisms, including the hard particle strengthening,fine-grain strengthening and solid solution strengthening.