| H13 hot work die steel has high high temperature strength,hardenability,wear resistance and resistance to cold and heat fatigue properties,so it is widely used internationally.However,when it is used for a long time under high temperature and high load,it will often lead to early high temperature wear failure.Therefore,it has important theoretical significance and engineering application value to improve the wear resistance of hot work die steel in harsh environments.In this paper,there were three kinds of Fe-Ni(containing 2%,5%,9% Ni)alloy coatings designed and laser cladding prepared,and they were microscopically analyzed and characterized by SEM,EDS,XRD,microhardness tester,etc.;The dry sliding wear experiment was carried out on Fe-Ni coating and H13 steel under different ambient temperature and loads.The morphology,composition,phase and hardness of their grinding surface and subsurface were tested and analyzed,the formation and function of the layer were studied,and the wear mechanism and anti-wear mechanism of the coating were explored.The results showed that the macro morphology of the laser cladding coating samples showed in turn: coating,heat-affected zone,substrate: coating,heat-affected zone,and substrate,and the coating and substrate were well combined,without pores,cracks and other defects.With the increase of nickel content,the microstructure and structure of the three Fe-Ni alloy coatings changed,along the direction from the bottom to the surface of the coating,the coating 1 appeared as cellular crystals,columnar dendrites,and equiaxed crystals;coating 2 presented cellular crystals,columnar dendrites,equiaxed crystals and columnar dendrites(overlap areas);coating3 was cellular crystals,columnar dendrites,a small amount of equiaxed crystals and coarse columnar dendrites(overlap area).From the results of backscattering and EDS analysis,it was found that the coating contains a large amount of Ti-based intermetallic compounds;according to XRD results,the matrix phases of coating 1and coating 2 with low nickel content were ?'-Fe,and the matrix phases of coating 3with high nickel content were ?'-Fe and ?-(Fe,Ni);the microhardness of the coating was obviously higher than that of the substrate,and the average hardness of each zone from high to low was: heat-affected zone,coating zone,H13 steel substrate zone.Thermal stability experiments showed that the thermal stability of the three coatings at high temperatures(especially 600°C)was significantly better than that of H13 steel.Wear experiments showed that the wear rate of coating 3 was the lowest at400°C-600°C,which was significantly lower than that of coatings 1,2 and H13 steel.It exhibited excellent wear resistance,especially at 600°C and 150 N.All layers had higher wear resistance than H13 steel.According to microscopic analysis of the polished surfaced,the wear resistance of the three Fe-Ni alloy coatings and H13 steel depended on the protective friction layer formed on the grinding surface and the thermal strength and thermal stability of the sub-surface layer.A large number of intermetallic compounds dispersed in the coating effectively strengthen the sub-surface layer,especially the ?-?' phase transformation of coating 3 was further strengthened during the wear process,so that the coating exhibited excellent abrasion resistance than H13 steel in the high temperature wear process(especially 600°C).According to the analysis of the friction and wear behavior of the coating and H13 steel,the characteristics of the grinding surface and the friction layer,it was found that the Fe-Ni coating exhibits oxidation mild wear,mild-severe transition of oxidation wear,severe wear,that was to say,coating 1,coating 2 and H13 steel were mainly oxidation mild wear at 400-500?,50-150 N and 600?,50 N,and severely worn at 600?,100N;while the wear mechanism of coating 3 was at 400-500?,50-150 N and 600?,50-100 N was oxidation mild wear.When it was in the transition zone between mild-severe transition of oxidation wear at 600? and 150 N,no severe wear occurs. |
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