| TiN is commonly used as a coating to modify the surfaces of mechanical parts,cutting tools,and abrasive tools.This application is based on the excellent properties of TiN,such as high hardness,low friction coefficient,and good corrosion resistance.However,the limited oxidation resistance of TiN results that it isn't suitable for high-temperature environments.To a certain extent,the addition of the third element makes up for the disadvantages of pure TiN in the actual working environment.Owing to the properties of high hardness,high-temperature oxidation resistance,and low friction coefficient,(TiCr)N composite coatings have been payed attention in recent years.Now,widely used methods of preparing(TiCr)N include reactive magnetron sputtering,physical vapor deposition,chemical vapor deposition,and cathode ion plating.Since most metal composite coatings and ceramic coatings can be prepared by plasma spraying,(TiCr)N coatings were prepared by a combination of plasma spraying and combustion synthesis(reactive plasma spraying).A new method was provided for the preparation of composite nitrides.In this work,it was found that(TiCr)N composite coatings needed to be sprayed in a high N2 gas concentration atmosphere,and the Ti-Cr powder used for spraying was subjected to metal reconstruction through thermodynamic analysis and previous experiments.A(TiCr)N composite coating was prepared via the reactive plasma spraying the metal reconfiguration powders of Ti and Cr.The phase composition,and microstructure of the(TiCr)N coating were investigated using X-ray Diffraction(XRD),X-ray Photoelectron Spectroscopy(XPS)and Scanning Electron Microscope(SEM).The existing status of Cr atoms in the coating were analyzed.Lattice structure and the elemental composition of the prepared(TiCr)N coating were analyzed using Transmission Electron Microscope(TEM)and Energy Dispersive Spectrometer(EDS).The effects of Cr content on the hardness and wear resistance of(TiCr)N composite coatings were studied through comparative experiments.The TiN coating and the(TiCr)N composite coating were treated in high-temperature of 600°C,700°C,and 800°C.The high-temperature oxidation resistance was analyzed by recording the rate of oxidative weight gain and surface phase changes.It was found that the(TiCr)N composite coating consisted of(TiCr)N and Cr phase.The microstructure of(TiCr)N was nanocrystals with a size range of 50-150nm.The Cr atoms completely entered the TiN lattice when the Cr content in the Ti-Cr reconfiguration powder was lower than 15wt.%.However,when the Cr content in the powders surpassed the 20wt.%,elemental Cr appeared in the composite coating.Cr atoms substituting Ti entered TiN lattice,which caused a certain degree of lattice distortion and the Cr atoms inhibited the high-temperature oxidation of Ti atoms during the spraying process,resulting in the hardness of composite coatings was higher than that of the TiN coating.The hardness and wear resistance of(TiCr)N coatings were affected by its Cr content.When the Cr content was below the 15wt.%,the hardness and wear resistance of the(TiCr)N coating were enhanced with the increase of Cr content,and the Cr content was higher 15 wt.%,The hardness and wear resistance of(TiCr)N coatings decreased with increasing Cr content.The(TiCr)N composite coating has significantly lower oxidation weight gain rate than the TiN coating.At the oxidation temperature of 600°C,TiN coatings has been oxidized,while on the surface of(TiCr)N composite coating with 15wt.% and 30wt.% Cr,(TiCr)N phase can be detected,which indicates that the doping of Cr element can significantly improve the high-temperature oxidation resistance of(TiCr)N coatings... |
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