Microstructure And Properties Of In-situ Ceramic Particles Reinforced Ti-based Composite Coatings

In order to solve the problem of poor oxidization and poor wear resistance of titanium alloy in high temperature,in-situ ceramic particles reinforced Ti-based composite coatings were prepared by plasma spray welding with the mixture of pure Ti?pure Cr and Ni powders.The phase composition and microstructure of the composite coatings were analyzed,and friction wear test and high temperature oxidation test were used to evaluate the composite coatings.By orthogonal optimization test,the optimized parameters was:welding current 63 A,welding speed 0.9mm/s,powder feeding speed 7.5g/min,plasma gas 3.5L/min,shielding gas 6.5L/min,transporting powder gas 4.5L/min.The results showed the composite coatings were mainly composed of Ti N?Ti2N?Cr N?Ti?Ti Ni.The interface between Ti N and Ti formed an almost perfect coherent interface due to the 13°6? difference in crystal orientation and the close interplanar spacing.From the fusion line to coatings upper,the microhardness gradually increased.The maximum microhardness of composite coatings was 967 HV0.5,which is about 3 times of the base metal.The results of the wear test at room temperature showed that with the increase of load,the wear loss and friction coefficient of composite coatings increased.The wear loss and friction coefficient also increased with the increase of the rotate speed.The wear mechanism of composite coatings under room temperature frictional wear test was slight adhesive wear and abrasive wear.In the high temperature friction and wear test,with the increase of load and rotate speed,the change of wear weight loss and friction coefficient was similar to that of room temperature friction and wear,and the wear mechanism was oxidation wear,adhesive wear and slight abrasive wear.The wear resistance of composite coatings was higher than that of the base metal at room temperature and high temperature tests.During the constant temperature oxidation test,the high temperature oxidation kinetics curve of the base metal was linear,and the surface oxidation failure was serious.The thermostatic oxidation kinetic curve of the strengthened layer basically conforms to the parabolic law,and the weight gain is larger at the initial stage of oxidation,while the weight gain decreases after the formation of the light blue dense oxide film.During cyclic oxidation,with frequent changes in heat and cold,the oxidation gain curve fluctuated greatly,among which the base metal gained the most weight,and the oxidation gain of the strengthened layer gradually.The oxide film of composite coatings was composed of Ti O2 on the surface layer and Cr2O3 and Ni O below,among which,Cr2O3 oxide film and Ni O oxide film play a major role in resisting high-temperature oxidation.