| When mechanical equipment works in extreme environments such as high speed,high temperature,high pressure,corrosion and heavy load,it is easy to cause surface damage of parts,The traditional surface coating strengthening technology can greatly improve the corrosion resistance and wear resistance of parts,but the bonding strength between the strengthened coating and the substrate workpiece is low,and it is easy to peel off under high temperature and high pressure,which can not meet the requirement of prolonging the service time of equipment.Induction cladding is a new surface modification or repair technology,which can prepare highperformance coating with uniformity and close combination with substrate at low cost,and has a wide application prospect.In this paper,the WC/Ni60 composite coating was coated on the surface of 45 steel by high frequency induction cladding technology,and the systematic research was carried out by means of numerical simulation,experiment and theoretical analysis,and the following achievements were obtained:(1)Using COMSOL finite element analysis software,the high-frequency induction temperature field simulation and experimental verification were carried out on the substrate without prefabricated coating and the substrate with prefabricated coating respectively,and the temperature field variation law including temperature distribution and temperature rise curve and the heating time range of high-frequency induction cladding WC/Ni60 composite coating were determined.The simulation of substrate temperature field without prefabricated coating shows that at any time point of induction heating,the maximum temperature appears on the substrate surface.During the whole heating process,the temperature rise process of substrate surface is divided into high-speed heating stage and medium-high-speed heating stage.The simulation of temperature field of substrate with prefabricated coating shows that the temperature decreases gradually along the radial direction from the substrate surface to the substrate core and the coating top,and along the axial direction from the middle position of the coating to the left and right sides.Combined with the melting point of the coating and the simulation results,the heating time range of high frequency induction cladding WC/Ni60 composite coating is preliminarily determined to be 18s-21 s.(2)According to the induction cladding time range obtained by finite element analysis,several groups of composite coatings with different cladding time were prepared by using high frequency induction cladding technology.The changes of external morphology,element distribution,phase distribution,microhardness and gradient state of composite coatings during cladding process were studied.The results show that with the cladding process,the powder coating melts gradually,and when it reaches a certain cladding temperature,the coating has the best surface morphology.If the cladding continues,the coating will overflow and the surface forming quality will become worse.During the cladding process,the atomic diffusion in the coating is strong,and the content of Fe element is increasing continuously.The floc crystals dominated by Fe-Ni solid solution Fe Ni3 and hexagonal crystals dominated by Cr carbides Cr7C3 and Cr23C6 change most significantly.The hardness value at the top of the coating is the highest.From the top to the bottom of the coating,the hardness distribution of the coating has a gradient decline state.When the coating exceeds the optimal cladding temperature,the hardness value of the coating will drop rapidly.There is a continuous unidirectional influence relationship between coating hardness change rule and coating phase,element,atomic diffusion and cladding time.(3)According to the optimum cladding time determined by experimental analysis,WC/Ni60 composite coating was prepared by high frequency induction cladding technology.The relationship between WC mass fraction and hardness,wear resistance and thermal expansion coefficient of composite coatings was studied,and the optimal WC mass fraction of high frequency induction cladding WC/Ni60 composite coatings was determined.The results showed that with the increase of WC mass fraction,the hardness of composite coatings increased,The hardness gradient state of the composite coating with WC mass fraction of 2%is the best;The addition of appropriate WC powder can significantly reduce the friction coefficient of composite coating and improve the wear resistance of composite coating surface;With the increase of WC mass fraction,the thermal expansion coefficient of composite coating decreases gradually.The effects of WC mass fraction on the microstructure,hardness,wear resistance and thermal expansion coefficient of the composite coating were comprehensively analyzed,and the optimum WC mass fraction of the high frequency induction cladding WC/Ni60 composite coating was determined to be 2%.The above research work can realize the surface repair and strengthening of shaft parts,provide theoretical basis and data support for the further development of surface engineering,and is of great significance for promoting the application of high-frequency induction cladding technology in industrial production. |
