Study On The Friction And Wear Performance Of Cr₂O₃/C Composite Coatings Used As Dynamic Sealing

Cr₂O₃ ceramic coatings have many excellent properties, such as low friction coefficient, high hardness, wear and corrosion resistances, etc.. Cr₂O₃ ceramic coatings prepared by plasma spraying have been successfully applied to the seals, leading to an extended working life, satisfied properties, lower cost and higher economic benefit.But in practical application, the seal is often failed due to spalling caused by poor working conditions and surface defects of ceramic coatings like uneven surface,pits and cracks. The low brittleness and toughness of ceramic coatings would make it more difficult to design, manufacture and package of sealing ring. In addition, the deficient surface performance is also the reason of limiting the widely application of the ceramic seal ring. The comprehensive performance of sealing rings can be improved by adding other materials in Cr₂O₃ coatings.In this study, the stainless steel（0Cr18Ni9） is chosen as the substrate, Cr₂O₃ composite coatings with different contents（0%, 5%, 10%） of diamond micro-powder were prepared by plasma spraying. The microstructure of coatings is analyzed by SEM and EDS. The tribological performance of coatings in dry grinding and 3% Nacl solution at room temperature were tested by highspeed linear reciprocating wear testing machine with different experimental parameters. The wear morphology of coating grinding cracks, wear debris and grinding ball is analyzed by SEM, EDS, optical microscope and threedimensional white light interferometer. The influence of diamond micro-powder on the friction and wear performance of Cr₂O₃ coatings are studied. The results as follows:1. The porosity of Cr₂O₃ composite coatings with（ 0%, 5%, 10%） diamond micro-powder is 15%,17%, and 12% respectively. And the surface hardness of three coatings is 840 HV, 810 HV, 980 HV respectively respectively.The hardness of Cr₂O₃ coatings with 10% diamond micro-powder with higher density is significantly improved.2. In the condition of load（20N） dry grinding, the friction coefficient and wear rate of Cr₂O₃ coatings with 10% diamond micro-powder are 0.06 and 9×10-16m3/N·m respectively, which are the lowest in three coatings. With load increasing, the friction coefficient of all three Cr₂O₃ coatings decreases and the wear rate of pure Cr₂O₃ coatings increases gradually, but the Cr₂O₃ coatings with diamond micro-powder show a falling wear rate. In three different loads,both the friction coefficient and the wear rate of Cr₂O₃ coatings with 10% diamond micro-powder are lowest and indicates the better wear resistance. The wear mechanism of pure Cr₂O₃ coatings under dry friction environment is microscopic disbonding and adhesive wear in low load, and abrasive wear in high load. Antifriction performance of Cr₂O₃ coatings with 10% diamond micropowder is better than that of pure Cr₂O₃ coatings..3. In 3% Nacl solution environment and the same load（20N）, the friction coefficient of Cr₂O₃ coatings after adding diamond micro-powder decreases, and both friction coefficient and wear rate of Cr₂O₃ coatings with 10% diamond micro-powder are lower in three coatings. The friction coefficient for all Cr₂O₃ coatings decreases with load increasing.The friction coefficient of Cr₂O₃ coatings with diamond micro-powder is lower than that of pure Cr₂O₃ coating’s. The wear rate of pure Cr₂O₃ coatings increases with the increase of load,but the wear rate of Cr₂O₃ coatings with diamond micro-powder increases first and then decreases. The wear mechanism of Cr₂O₃ composite coatings is mainly corrosive wear and abrasive wear mainly affected by hardness of coatings.But the increase of Cr₂O₃ coatings hardness with 10% diamond micro-powder is little,which can not resistance corrosive wear.4. The friction coefficient of Cr₂O₃ coatings after adding diamond micropowder is lower than that of pure Cr₂O₃ coating’s in dry grinding and 3% Na Cl solution.