Composition Selection And Performance Research Of 45 Steel Laser Chromium/Molybdenum/Boron Series Alloyed Coating

In order to solve the wear,corrosion and other failures of the screw surface of the injection molding machine,the composition,structure and performance of the coating are deployed to a greater extent,and the application of the coating is extended to components such as rollers,crankshafts,knife molds.In this paper,laser alloying technology was used to prepare chromium/molybdenum/boron series alloy coatings on the surface of 45 steel,and the composition ratio of alloying coating and corresponding alloying process were optimized.The corresponding relationship between the selection of ingredients and the performance of the alloyed coating was proposed to provide the corresponding coating composition and process for different engineering requirements.The conclusion is as follows:（1）The ternary series coatings of Cr₃Mo₇B_x,Mo₁B₉Cr_x and Cr₃B₇Mo_x were optimized and prepared,and the corresponding alloying process was obtained.The coating is composed of alloying zone and transition zone with an average thickness of about 1mm,of which the average thickness of the alloying zone is about 0.6mm.The alloying zone was divided into three parts:surface layer,center and transition zone.The surface structure is equiaxed crystal,the center is dendrite,and the transition zone is cellular crystal.The microstructure of the alloying zone is solid solutions and compounds such as Fe-Cr,Fe₂B,Fe-Mo,Cr₂B,Cr_xFe_y,and the hardness gradiently decreases from the surface to the inside.（2）In the chromium/molybdenum/boron series alloyed coatings,the hardness varies within the range of 597HV_0.1-1274HV_0.1,of which the B alloyed coating has the highest hardness of 1274HV_0.1 and the Cr alloyed coating has the lowest hardness,597HV_0.1.the wear rate varies from 0.571×10^-14m³/N·m to 3.050×10^-14m³/N·m,and the wear rate of Mo₁B₉Cr_23.3coating is the smallest,0.571×10^-14m³/N·m,the wear rate of Mo₁B₉Cr_1.1 coating is the largest,which is 3.050×10^-14m³/N·m.The corrosion resistance of neutral salt spray corrosion time varies from 15min to 36h.Among them,the corrosion resistance of Cr alloy coating is the best,36h,and the corrosion resistance of Mo₁B₉ alloy coating is the worst,15min.（3）The corresponding relationship among composition,microstructure and properties of chromium/molybdenum/boron series alloy coating was obtained,which provides technical guidance for different engineering requirements to select corresponding coating composition and process.