Cr₃C₂-NiCr/Mo Composite Coatings Of Wear And Corrosion Resistance For Ball Valve

As one kind of globe valve, ball valve was came out in the 1950 s and widely used in the fields of petroleum refining, water conservancy, electric power and long-distance pipeline. The researchers focus on improving working life of ball valve,which is short at present. In this article, we prepared composite coatings with mixed powder of Cr3C2-Ni Cr and different mass friction of Mo on 45 steel with supersonic flame spraying.Supersonic flame spraying(HVOF) has the advantage of high speed, low spray temperature; Cr3C2 has the advantage of oxidation resistance, wear resistance,corrosion resistance, high hardness and low density, what’s more, due to similar coefficient of thermal expansion, Cr3C2 combine compact with 45 steel; Mo has excellence bonding resistance and wear resistance properties and molybdenum oxide with excellence self-lubrication antifriction performance will produced at high temperature.OM, SEM, X-ray, microhardness tester, friction and wear tester, salt spraying tester and electrochemical workstation were used to investigate microstructure, phase,hardness, wear resistance property and corrosion resistance property.Supersonic flame spraying(HVOF) prepared Cr3C2-Ni Cr/Mo composite costings and the proportion of Mo were 0wt.%, 3wt.%, 6wt.%, 9wt.%, 12 wt.%. The result showed that except generated Mo O2, the microstructure of Cr3C2-Ni Cr coating did not change and the main phase were Cr3C2-Ni Cr, Cr3C2, Ni Cr, Mo and Mo O2.The hardness of Cr3C2-Ni Cr coatings decreased obviously with Mo. The hardness(HV0.05) of Cr3C2-Ni Cr/Mo composite coatings was the highest with 0wt.%Mo is 1120.2HV0.05, 1173.5HV0.1, 1197.6HV0.2, respectively, increaed 652%compared with 45 steel. The main wear mechanism was adhesive wear under low load, while, fatigue wear under high load. The friction coefficient values and abrasion were the lowest with 3wt.% Mo content.Salt spray test and electrochemical experiments were used tost corrossion resistance of Cr3C2-Ni Cr/Mo composite coatings. The salt spray corrosion from strong to weak were 3wt.%Mo, 12 wt.%Mo, 9wt.%Mo, 0wt.%Mo, 6wt%.Mo after 8h of salt spray.The electrochemical corrosion resistance of Cr3C2-Ni Cr/Mo in 5wt.%H2SO4 fromstrong to weak were 3wt.%Mo, 9wt.%Mo, 6wt.%Mo, 0wt.%Mo, 12 wt.%Mo. In3.5wt.%Na Cl 3wt.%Mo has the best corrosion resistance. Composite coatings with3 wt.% Mo showed excellence corrosion resistance.