Microstructure And Properties Of WxCrN And WZrCrCn Gradient Coatings

Tungsten coating with small grain size,high melting point,high hardness and other characteristics,can be used for cutting tools,valves,pipes and piston rod surface protection.More and more researchers have reported tungsten nitride PVD hard coating because of the change of phase structure,strong friction and wear resistance and high corrosion resistance.At present,coating research is developing towards a more innovative direction,aiming to break the bottleneck and further improve the mechanical and tribological properties of the coating,such as the design and improvement of the structure of the coating.In the existing reports of other gradient coatings,the multi-layer gradient coating prepared by innovative structural design of the coating has higher binding strength and coating quality than the single-layer coating,and effectively improves the plastic toughness and tribological properties of the coating.For desalination in the field of chemical industry and aerospace complex mechanical parts surface strengthening,this paper aims to explore reasonable proportion of tungsten tungsten nitride coating,not only has the remarkable performance of hardness,strength,still should dig the excellent properties of friction can be used in corrosive environment,and further to different tungsten coating do gradient design.In this paper,Wx Cr N coating(x=0,7.65 wt.%,19.02 wt.%,24.35 wt.%)and WZrCrCN gradient coating(x=0,7.65 wt.%,19.02 wt.%,24.35 wt.%)with four tungsten elements were prepared on austenitic stainless steel(1Cr17Ni8)by multi-arc ion plating.The main work is as follows:(1)For Wx Cr N coating,the influence of weight ratio of different tungsten elements on the microstructure and properties of the coating was investigated.Microscopic results show that the diffraction peak intensity of Cr N phase(110)decreases while the peak intensity of Cr N phase(200)increases.The main phase is the mixed phase composed of Cr N,?-WN,?-W₂N and Cr₂N.The W content changes the relative proportion of Cr in the coating,and the?-WN phase content gradually exceeds that of?-W₂N phase with fine grain.At the same time,the number of metal phases formed by tungsten and chromium increases.The hardness of W_24.35Cr N coating is increased to three times that of stainless substrate,and the corrosion current density of W_7.56Cr N coating is reduced by two orders of magnitude compared with that of stainless substrate,showing the best corrosion resistance.(2)For WZrCrCN coating with different structural gradient,the main phases are Zr N,Cr N and Cr₂N,showing a preferred orientation of(200).The rare metal Zr further refines the grain size of the coating,and all the four structures show fine grain strengthening phenomenon.The maximum vickers hardness is about 2100HV_0.1 when the thickness of the coating is about 8.5?m.The hardness,wear resistance and deformation resistance of the gradient coating are effectively improved by introducing Zr element with high strength and high activity into the surface layer and conducting structural gradient design of the coating.However,the toughness of the gradient coating is relatively decreased due to the influence of the inevitable residual stress between each layer.In conclusion,the comprehensive performance of WZrCrCN gradient coating with rational design of coating structure is improved compared with WCr N coating.(3)Under the condition of oil lubrication,the friction coefficient of the four Wx Cr N coatings fluctuates from 0.11 to 0.17,and increases rapidly and then gradually stabilizes at0.16,forming a stable oil film on the coating surface.The friction coefficient of WZrCrCN gradient coating is between 0.11 and 0.12,and the wear resistance of the gradient coating is greatly improved.WZrCrCN coating shows high bonding strength and friction and wear resistance.This is because the gradient coating with different structure design has multi-level protection effect on matrix in friction test,and Zr element plays fine grain strengthening effect.