Study Of Alloy Element On Microstructure And Mechanical Property Of The M2 High Speed Steel Coating Produced By Laser Cladding

The effects of vanadium,boron and silicon on the microstructure and mechanical properties of M2 high speed steel coating were investigated.The microstructure and properties of M2 high speed steel coating by laser cladding of vanadium,boron and silicon were studied.The effects of vanadium,boron and silicon in in the laser cladding process and the best heat treatment process of vanadium,boron and silicon-M2 laser clad high speed steel were obtained,which provided theoretical support and basis for the production of high strength wear-resistant materials.In this thesis,the OM,SEM and XRD were used to characterize and analyze the microstructure and phase composition of the coating.Through the analysis of the hardness,red hardness and high temperature wear properties of the coating,The optimization of heat treatment process parameters and the mechanism of alloying elements were discussed.The results are as follows:The optimum heat treatment process of vanadium-M2 laser cladding high speed steel is at560 ? for 1 h×1 time.The microstructure of M2-3% V and M2-4% V high speed steel are martensite,M2 C carbide and retained austenite;The microstructure of M2-3% V and M2-4% V high speed steel after heat treatment is tempered martensite and carbide M2C;The microstructure of M2-8% V high speed steel is ferrite and carbide.M2-3% V coating showed high hardness,reaching 858 HV and red hardness value of 643 HV.With the increasing of vanadium content(> 3%),the hardness and red hardness of laser cladding high speed steel decrease,and the wear resistance showed the trend of deterioration.The wear mechanism of vanadium-M2 laser cladding high speed steel is mainly in the form of stripping layer abrasion and abrasive wear,M2-3% V and M2-4 % V is mainly in stripping layer,M2-8% V is mainly abrasive wear.The optimum heat treatment process of boron-M2 laser cladding high speed steel is at560 ? for 1 h ×3 times.The solidified microstructure of the boron-M2 laser cladding highspeed steel is martensite,reticular M2(C,B)Carbides and retained austenite;the heat-treated microstructures are tempered martensite and reticular M2(C,B)carbides.With the increasing of boron content,the hardness and red hardness of laser cladding high-speed steel coating increased slightly and became stable,and the wear resistance decreased.The hardness of M2-0.5% B reached 889 HV,red hardness reached 744 HV.The wear mechanism of boron-M2 laser cladding high-speed steel is mainly abrasive wear and stripping wear.M2-0.05% B is mainly abrasive wear,M2-0.3% B is both abrasive wear and stripping wear,M2-0.5% B is mainly the stripping layer wear.The optimum heat treatment process of Si-M2 laser cladding high-speed steel coating is at560 ?for 1h ×1 time.The solidified microstructure of the boron-M2 laser cladding high-speed steel is martensite,reticular M2 C Carbides and retained austenite;the heat-treated microstructures are tempered martensite and reticular M2 C carbides.With the increasing of silicon content,the hardness and red hardness of the laser cladding high speed steel coating are gradually increased,and the wear performance is slightly reduced.M2-1.0% Si sample hardness reaches 882 HV,red hardness reaches 625 HV.The wear mechanism of silicon-M2 laser cladding high-speed steel is mainly in the form of stripping wear.