Study On Laser Cladding WC/Ni60A Composite Coating And Its Wear And Corrosion Resistance

The workpieces used in marine engineering equipment are vulnerable to the double damage of corrosion and wear,which requires the coating material not only to have good wear resistance,but also to have a strong resistance to seawater corrosion.Therefore,in this study,WC ceramics with high hardness and chemical stability were selected as the reinforcing phase,and Ni60A self-soluble alloy powder was used as the binder to prepare high-quality WC reinforced Ni-based composite coatings on H13 steel and nickel-al-bronze substrates by laser cladding technology.The phase composition,microstructure,corrosion and wear resistance of the coating were systematically analyzed by a variety of characterization testing methods,and the corrosion and wear resistance mechanism of the coating was revealed.（1）The surface cladding parameters of H13 steel and Ni-Al bronze were determined by orthogonal test.The results show that the scanning speed has the most obvious effect on the forming quality of cladding layer,and the forming quality of cladding layer increases with the increase of scanning speed.The hardness of coating surface is controlled by powder feeding rate and cladding power.With the increase of powder feeding rate and cladding power,the hardness of coating increases.The optimal laser cladding parameters of H13 steel and Ni-Al bronze were determined based on the forming quality and hardness of cladding surface.（2）Based on the optimized process parameters,the effects of different WC content（x wt.%）on the microstructure and properties of composite coating on the surface of H13 steel were explored.It is found that when 15≤x≤25,the coating phase composition has no obvious change,the microstructure is gradually refined evenly,and the hardness and corrosion resistance and wear resistance are gradually improved.However,when x≥35,the composite coating appears a large number of holes,cracks and other defects.Therefore,25 wt.%WC/Ni60A composite coating has the best comprehensive performance,and based on this composition,the effect of graphite powder addition on WC/N60A composite coating was studied.（3）Multilayer graphene was prepared by ultrasonic stripping combined with wet ball milling,and 25 wt.%WC/Ni60A composite coating with different content（y wt.%）graphite powder was added on the surface of H13 steel.The results show that when y=1.0,the hardness,wear resistance and corrosion resistance of the composite coating are significantly improved.It shows that the addition of graphite not only promotes the homogeneity of the coating microstructure but also provides lubrication efficiency.（4）Based on optimized process parameters and the above research results,direct cladding of 25 wt.%WC/Ni60A composite coating was performed on the surface of nickel-Al bronze,and the effects of powder milling time and the addition of rare earth oxide CeO₂ on the microstructure and properties of the coating were studied.The results showed that the microstructure of the coating was further refined with the increase of milling time,and the corrosion and wear resistance were improved obviously.The addition of appropriate amount（z wt.%）CeO₂ also contributes to the uniform refinement of the coating structure.Therefore,when 1.0≤z≤1.5,the composite coating has better wear resistance and corrosion resistance.However,when z=2.0,the element segregation phenomenon of coating is obvious,the homogeneity of the coating structure is reduced,and the wear resistance and corrosion resistance are significantly decreased.