| Plasma spraying technology has the advantages of wide range of spraying materials,strong adhesion of coating and high efficiency of spraying.It plays an important role in wear resistance,corrosion resistance,thermal barrier and insulation.The coating is made up of particles stacked flat by layer.Inevitably,there are defects such as pores and cracks.The application of these coatings in some key structures has been greatly restricted.In order to solve the above problems,the plasma sprayed NiCrBSi coating on the surface of 2Cr13 martensitic stainless steel was first prepared,and then the coating was treated by furnace remelting and plasma flame remelting.The microstructure and properties of the coating were compared and analyzed,and the effects of different remelting processes on the microstructure,microstructure,porosity,hardness and wear resistance of the coating were investigated.On this basis,the spray / remelting composite coating was prepared by furnace remelting and plasma flame remelting,and the microstructure and properties of the composite coating were compared.Plasma spraying coating is a layered structure formed by the deformation of sprayed particles,oxides,microcracks and pores.The coating and matrix are combined mainly by mechanical occlusion.After remelting and plasma remelting in the furnace,the original micropore and micro crack in the coating gradually disappeared,and the coating changed from a loose stacked structure to a more homogeneous and compact structure.After remelting at four different temperatures at 950-1100 C,the porosity of the coating decreased from 4.26% to 0.84%~1.38%,and the porosity of the plasma flame remelting coating was 0.60%.After remelting,the interaction,diffusion and aggregation of the elements between the substrate and the coating are changed from mechanical occlusal to metallurgical bonding.The microhardness of the coating is increased from 687.42 HV to 766.48 HV by plasma flame remelting.With the increase of remelting temperature in the furnace,the dispersion hard phase in the coating gradually grows,and the hardness of the coating is improved.When the remelting temperature reaches 1100 degrees,the dispersive phase grows and aggregates and distributes more centrally,which reduces the effect of dispersion strengthening.At the same time,the wear resistance of the coating was improved by remelting treatment,and the wear form of the coating changed from abrasive wear to adhesive wear.According to the polarization dynamic potential curve,the self corrosion potential of the coating and the plasma flame remelting coating is-0.647 V and-0.609 V respectively.The corrosion current is 3.578E-08 A.Cm-2 and 6.837E-10 A cm-2 respectively.The corrosion resistance of the plasma flame remelting coating is better than that of the plasma spraying coating and the remelting coating in the furnace.In the plasma sprayed / remelting composite coating,there is no good mechanical bond between the coating and the coating,and the coating is prone to peeling.The coating of plasma spraying / remelting composite structure is good,and there is no obvious dividing line between the coatings.The diffusion of the elements at the boundary of the coating will occur,and the coating can form a better metallurgical bonding.At the same time,in the plasma spraying / remelting composite coating,the average hardness of the remelting coating increases with the increase of the distance between the interface and the interface of the matrix / remelting coating. |
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