Study On The Microstructure And Properties Of Poatings Prepared By Oxygen Acetylene Thermal Spraying And Physical Vapor Deposition

At present,with the rapid development of surface engineering technology,the technology of coating and film preparation on metal surface is gradually mature.Ball valves and valves,as important industrial transmission links,act as transmission media and control fluid direction.Because of the special working conditions of ball valves and valves,the mechanical properties of parts have high requirements.Generally,the mechanical properties of metal parts are improved by heat treatment and the addition of appropriate trace elements,but these traditional methods can not meet the special working environment of parts,so it is necessary to prepare coating on the metal surface to meet the complex working conditions and extend the service life.In this paper,Co base alloy coating is successfully prepared by oxyacetylene thermal spraying,and TiN,CrN and DLC films（diamond-like films）are successfully prepared by vacuum evaporation in Physical Vapor Deposition（PVD）and vacuum cathode arc ion plating.The microstructure and mechanical properties of coating and film were analyzed.This paper is mainly divided into the following parts:1.Using oxy-acetylene thermal spraying to prepare a single layer of Co-based alloy coating and study the microstructure and mechanical properties:The Co-based alloy coating was successfully prepared by oxyacetylene thermal spraying technology.The coating structure was analyzed by XRD and metallographic microscope as Cr₇C₃,Co₇C₃,Cr₂₃C₆,Co₂₃C₆,etc.（hereinafter referred to as MC class metal carbide,M refers to metal element,corner mark refers to atomic ratio）.And these hard carbides are an important cause of coating hardness increase.According to SEM,the coating structure is relatively dense,but cracking and unfused particles occur in some areas of the coating due to the uneven temperature or distance of the spray gun.In addition,through the microhardness analysis,the hardness of the coating and the substrate is almost three or four times higher than that of the substrate,and the wear resistance of the coating is improved,because M₂₃C₆,M₇C₃ and other hard carbides are generated in the prepared coating structure,which increases the wear resistance of the coating with increased hardness.In addition,the corrosion resistance is further optimized through the preparation of the coating.Because the substrate structure is relatively dispersed,the preparation of coating on the surface makes the structure more dense and reduces the generation of pores.Meanwhile,the coating contains Cr and other elements to generate a dense oxide layer on the surface,so the corrosion resistance of the coating is improved.2.Preparation of TiN,CrN and DLC single-layer films by PVD:TiN,CrN and DLC single-layer films were prepared by vacuum cathode arc ion plating.It was found that CrN films produced Cr₂N phase,TiN films showed obvious preferred orientation of characteristic peaks and high crystallinity,while DLC films were amorphous films.By analyzing the mechanical properties of the three single-layer films,the hardness and plastic deformation ability of DLC films are the highest,which is because as an amorphous film,there are many defects and distortions,so the hardness and plasticity are high,followed by TiN and CrN films.TiN films have smooth surface and better quality than CrN films,so the performance is better than CrN films.3.The TiN,CrN and DLC composite films based on Co coating were prepared by PVD.Firstly,the TiN composite films based on Co coating were prepared by vacuum evaporation and vacuum cathode arc ion plating.The mechanical properties were compared.The TiN films prepared by cathode arc ion plating have better quality than those prepared by vacuum evaporation,and their hardness,wear resistance and plastic deformation ability are higher than those prepared by vacuum evaporation.Secondly,the mechanical properties of TiN,CrN and DLC composite films prepared by the same technology are compared.The results show that DLC as amorphous films has the best comprehensive properties,followed by CrN and TiN filmsIn summary,the quality of the composite film is superior in that of the single-layer film prepared by vacuum cathode arc ion plating.The plastic deformation ability is improved,the structure is relatively dense,and the corrosion resistance is good.Moreover,the hardness and wear resistance of the composite film are better than those of the single-layer Co based alloy coating,so the comprehensive mechanical properties of the composite thin film are the best.Compared to Co based coatings prepared by oxygen acetylene thermal spraying,PVD technology can better reduce industrial costs and optimize coating quality.