Study Of Coatings On Steel Sprayed By A Novel High Pressure HVOF

High velocity oxygen-fuel flame (HVOF) is one of the advanced surface modificationtechnology, which can replace hard chromium electroplating plating technique. In order to make abetter evaluation of the abrasion and corrosion resistance on the aircraft landing gear and othercomponents, systematic study of spray coating process for its preparation affect the performance ofthe substrate an issue that needed to be addressed as a matter of urgency. Therefore, WC-10Co4Crcoatings and WC-12Co coating was successfully formed on the surface of the steel by HVOFparameters. The structure and properties of the coating was studied by OM, SEM, EDS, XRD and soon. To simulate accelerate corrosion behavior in marine and atmospheric environment, the salt spraycorrosion test were operated. In this study, the corrosion resistance and mechanism were discussed.The results show that, WC-12Co and WC-10Co4Cr coating deposited by HVOF parameters havefine surface, even crystal size, good adhesion and low porosity. Also there were no the pores andcracks on the coating. It is mechanical integration between coating and the substrate. The main phaseof WC-12Co is W2C and brittle η phase Co6W6C. The main phase of WC-l0Co4Cr is W2C and CoCrphase. The hardness of the WC-12Co and WC-10Co4Cr coating are three to four times higher thanthat of the substrate, and that of the WC-10Co4Cr coating was highest.The result of the friction and wear test show that wear-resisting of the substrate was significantlyimproved by the WC-12Co and WC-10Co4Cr coating. And the wear resistance of the WC-10Co4Crcoating was the best. In the following experiment conditions: room temperature, load430g,slidingspeed840r/min, GCr15as the friction pair, the main mechanism of WC-10Co4Cr is abrasive wear,the main mechanism of WC-12Co is surface fatigue, and the main mechanisms of the substrate areadhesive wear and oxidation wear.The result of electrochemical corrosion test and salt spray test show that the corrosion resistanceof WC-10Co4Cr and WC-12Co is better than that of substrate，and the WC-10Co4Cr has maximumcorrosion resistance. The observation and the phase and chemical composition analysis of coatingsurface draw the mechanism of corrosion failure. The main corrosion mechanism of WC-12Co isbinder phase corrosion and galvanic corrosion between WC and Co results to WC particles removal.Pore and inhomogeneity in WC-10Co4Cr are seen as the original of corrosion. The main corrosionmechanism is protection of the Cr2O3passive film, partial binder phase corrosion and WC particlesremoval.