Effect Of Nickel Coated Graphitecontent On The Structure Andproperties Of TiN-Ni/G Compositecoatings

Ti N coatings on the surface of metal substrate have high hardness,good wear resistance and good chemical stability.However Ti N ceramic are brittle material,which are easy to peel off under severe erosion and wear conditions,and the damage to the friction pair is large in the friction process.In order to utilize the excellent performance of Ti N,the solid lubricant Ni/G was added into the Ti N coating by reactive plasma spraying to improve the anti-wear properties of Ti N.The preparation process of Ti N-Nickel coated graphite(Ni/G)composite coating was optimized.The microstructure of Ti N-Ni/G coating was analyzed,and the friction and wear properties of the coatings were tested.The abrasion resistance of the composite coating was tested in different abrasive media.The micro-hardness and the weight loss of the mill were used as evaluation indexes,and the coating preparation process was optimized by orthogonal test.When the micro-hardness is used as the reference standard,the optimum process is nickel-coated graphite content of 8wt.%,spraying power of 30 k W,and spray gun distance of 100 mm.When the weight loss of the mill is used as the reference standard,the optimum process is the nickel-coated graphite content of 11wt.%,the spraying power of 30 k W,and the spray gun distance of 100 mm.the composite coating has the best performance.The composite coatings are mainly composed of Ti N,Ni,C and Ti₃O with well combined interface and high density.With the increasing of Ni/G content,the height of Ti₃O peak decreases,which indicates that the increase of Ni/G is beneficial to inhibit the formation of Ti₃O.The existence of C-N bonds and N-(Ti,C)bonds indicates that some C has been into the Ti N lattice.With the increase of Ni/G content,the fracture morphology fluctuates slightly,the granular structure increases,and the dimples appears on the fracture surface.The fracture form of the coating changes from brittle fracture to brittle fracture and ductile fracture.As adding Ni/G,the micro-hardness of Ti N-Ni/G composite coatings decreases.The hardness of the composite coatings is about 1000 HV_0.2.When adding to 8wt.%Ni/G,the hardness of the composite coatings is the highest.With the increase of spraying power,the friction coefficients of the composite coatings decreases,and the lowest friction coefficient is got when power is 30 k W.With the increase of Ni/G content,the wear weight loss of composite coatings increased first and then decreased.When the content of Ni/G reached to 8wt.%,the wear rate shows to be the highest.The wear resistance of Ti N-11wt.%Ni/G composite coating is best.The abrasion resistance of the composite coating was tested in Si O₂grit and liquid composed of different corrosive media.When the p H of the abrasive solution is 4,the mass loss of the Ti N-11%Ni/G coating is the lowest;when the p H is 7,the mass loss trend is the same as above;when the p H is 10,the quality loss trend of the composite coatings with different content is basically the same.With the increase of p H value,the weight loss of the composite coating shows a decreasing trend.The abrasion resistance of Ti N-11wt.%Ni/G composite coating is the best.