TC4 钛合金表面超音速火焰喷涂防护涂层及其摩擦学性能研究OA北大核心CSTPCD

The wear resistance of titanium alloy is one of the most important factors which affect its performance and service life.In previous studies,the wear resistance of titanium alloy surface protective coatings was mainly researched with stainless steel and Si3N4 ceramics as friction pairs,and there was a lack of research on the wear performance between the protective coating and titanium alloy.In order to reduce the abrasion and find out a wear-resistant coating system that is applicable for the friction between titanium alloy parts,Cr3C2-NiCr,Ni50,and NiCr coatings,with high,medium,and low hardness,respectively,were sprayed on the surface of TC4 titanium alloy by HVOF.A scanning electron microscope(SEM)and a microhardness tester were used to analyze the microstructure and mechanical properties of the coatings.The tribological properties of the coatings in friction with TC4 titanium alloys were measured with a versatile friction and wear test machine.The results of the mechanical and wear test results showed that the hardness of Ni50 and NiCr coatings was lower than that of the Cr3C2-NiCr coating.The lower hardness of Ni50 and NiCr coatings lead to the cracks generated at particle interfaces that around the indention when they were subject to a load of 49 N.However,differ from the crack morphology of Ni50 and NiCr coatings,the cracks in higher hardness Cr3C2-NiCr coatings propagated along the particle interface.The fracture toughness of the two coatings was 3.58 MPa·m1/2 and 1.69 MPa·m1/2,respectively,which were lower than that of Cr3C2-NiCr coatings with a value of 3.65 MPa·m1/2.The hardness of TC4,Cr3C2-NiCr,Ni50 and NiCr coatings were 314HV0.3,1 120HV0.3,680HV0.3,and 438HV0.3,respectively.However,the Ni50 coatings,as well as,the TC4 friction pair that was in friction with Ni50 coatings showed the lowest specific wear rate and wear loss,with the value of 0.87×10-7 mm3/(N·m)and 2.84 g,respectively.The coating specific wear rate of Ni50 coatings was 2.53,0.84,and 0.08 times than TC4 alloy,Cr3C2-NiCr,and NiCr coatings,respectively.Meanwhile,the wear loss of the TC4 friction pair in friction with Ni50 was 1.1,0.3,and 0.04 times than the friction pair that was in friction with TC4 alloy,Cr3C2-NiCr,and NiCr coatings,respectively.The wear mechanism of the TC4 substrate in friction with TC4 was adhesive wear,which was same with NiCr coatings in friction with TC4 friction pairs.Due to the low fracture toughness,the NiCr coating sufferred a much greater wear loss than Cr3C2-NiCr and Ni50 coatings.The wear mechanism of Cr3C2-NiCr coatings and TC4 friction pairs was adhesive wear and abrasive wear,resulting in a significant cutting effect and leading to a greater wear loss of TC4 friction pairs.The Ni50 coatings showed a moderate hardness but a relatively large fracture toughness compared with Cr3C2-NiCr and NiCr coatings.The cutting effect and adhesion effect of Ni50 coatings on friction pairs was lower than that Cr3C2-NiCr coatings and NiCr coatings,respectively,and the wear loss of the coatings and friction pairs was lower than the other two.In summary,the Ni50 coatings prepared by HVOF can reduce the adhesion wear loss of TC4 titanium alloy substrates and friction pairs.This study provides a feasible scheme for the design of wear resistant coatings on titanium alloy surfaces and for the improvement of friction properties between titanium alloy parts.