Wear-Resistant And Anti-oxidation Coating On The Surface Of Valve Seat Hole Material Organization And Performance Research

As an important part of the engine,the valve seat ring is embedded in the contact position of the cylinder head and the valve,and cooperates with the valve to form a closed space to protect the cylinder head.The performance of the valve seat ring will affect the output power and service life of the engine.In recent years,with the continuous improvement of industrialization,the working conditions of valve seat ring have become more and more severe.Each year,the amount of valve seat ring loss in the world due to wear and high temperature oxidation accounted for about 10%of the total steel output in that year.According to statistics,the number of unsafe engine failures caused by valve seat failures has increased year by year,so the valve seat surface modification research is very necessary.In this paper,multi-arc ion plating technology was used to prepare CrAlTiN coating on the surface of vermicular graphite cast iron valve seat material,and the influence of Al and Ti elements on the coating structure and mechanical properties,tribological properties,and high-temperature oxidation properties were systematically studied.papers,scanning electron microscopy(SEM)and white light interferometer were used to characterize the surface structure and three-dimensional morphology of coating;transmission electron microscope(TEM)was used to analyze and observe the internal microstructure of the coating;modern analysis techniques such as(XRD)and X-ray photoelectron spectroscopy(XPS)were used to detect the structure and phase composition of the coating,and the qualitative and quantitative analysis of the coating was completed;the nano-indentation instrument was used to measure the nano-hardness and elastic modulus of the coating;the high temperature friction and wear tester and the coating adhesion automatic scratch tester was used to determine the coating friction coefficient and the film-base bonding force;the high-temperature oxidation furnace was used to perform the high-temperature oxidation experiment.Research indicates:(1)The CrN coating is prepared via multi-arc ion plating technology.The grain size and surface roughness of the coating surface gradually grow with the increase of Cr target current.The growth method of the coating is columnar growth.When the Cr target current is 50A,the surface structure of the coating uniform,with a minimum roughness of 18.46nm;the coating is composed of Cr elemental,typical NaCl face-centered cubic structure of CrN and hexagonal structure of Cr₂N phase;the coating of cross-sectional morphology is continuous and dense,is divided into matrix and transition layer Cr and working layer CrN;coating film base bonding force,nano-hardness and Young's modulus shows a trend of first increasing and then decreasing with the increase of Cr target current;when the Cr target current is 65A,the coating bonding force has a maximum value of 49.2N,The friction coefficient is 0.5,the maximum nano-hardness is 18.844GPa,and the Young's modulus is 254.289GPa;the oxidation weight gain rate curve of the coating conforms to the power exponential function,and the main products after oxidation are Cr₂O₃ and Fe₂O₃;the oxidation rate of the coating is 0.0049 after oxidation 0-450h,the oxidation rate of the coating is 0.0021mg·cm^-2·h^-1 when oxidized for 450-500h.It can be concluded that the wear resistance and oxidation resistance of the CrN coating are insufficient.(2)The CrAlN coating is prepared by multi-arc ion plating technology.The particle size,density and surface roughness of the coating surface are directly proportional to the Al target current.When the Al target current is 60A,the surface grain size of the coating is uniform,the roughness is 1.139?m,and the coating thickness is 2.81?m;with the increase of the Al target current,CrN peak intensity gradually weakened,the coating is composed of CrN,AlN,CrAlN,Al₂O₃ and Cr₂O₃ phases;the coating of cross-sectional morphology is continuous and dense,the coating layer is obvious,and the regularity is strong;the coating film-base bonding force varies with Al The target current increases first and then decreases.When the Al target current is 60A,the film-base bonding force has a maximum of 54.1N,the friction coefficient is 0.48,and the wear mechanism is abrasive wear;the nano-hardness,Young's modulus and The Al target current is proportional.When the Al target current is 65A,the nano-hardness and Young's modulus have the maximum values of 22.1116GPa and 320.1217GPa;the oxidation weight gain rate curve of the coating conforms to the power exponential function,and the main products after oxidation are Cr₂O₃,Al₂O₃,oxidation 0-450h coating oxidation rate 0.003 mg·cm^-2·h^-1,oxidation 450-500h coating oxidation rate 0.000064m2·cm^-2·h^-1.The analysis results show that Al doping significantly improves the oxidation resistance of the CrN coating,but the friction coefficient is still relatively large.(3)The CrAlTiN coating is prepared by multi-arc ion plating technology.The grain size and surface roughness of the coating increase with the increase of the Ti target current.When the Ti target current is 65A,the coating structure is better,the density is higher,the surface roughness is 1.250?m,and the coating thickness is 3.41 ?m;the coating is mainly composed of CrN,AlN,TiN,CrAlTiN,Cr₂O₃ and Al₂O₃ phases;the cross-sectional morphology of the TEM coating is used to shows that the coating has strong regularity,and the coating layer and island alternately exist,and there is a certain degree of lattice distortion;the coating film base The binding force,nano-hardness and Young's modulus first increase and then decrease with the increase of Ti target electricity.When the Ti target current is 65A,the maximum binding force is 65.1N,and the nano-hardness and Young's modulus are 23.477GPa and 331.141GPa;The coating friction coefficient first decreases and then increases with the increase of the Ti target current.When the Ti target current is 65 A,the coating friction coefficient is at least 0.38,and the wear mechanism is abrasive wear.The oxidation weight gain rate curve of the coating conforms to the power exponential function.The product Cr₂O₃,Al₂O₃,TiO,the oxidation rate of the coating is 0.0027 mg·cm^-2·h^-1 for 0-450h,and the oxidation rate of the coating is-0.00005 mg·cm^-2·h^-1 for 450-500h.The wear resistance of the CrAlN coating after doping with Ti is significantly improved,and the hardness and bonding force are significantly improved.