Supersonic flame spraying ceramic coating of metal wear resistance and corrosion resistance
Yin Aoyu
CNKI
ABSTRACT：This paper, based on the research of High velocity oxy-fuel spraying(HVOF) to replace the traditional hard chromium plating technology,which to solve the problem of high efficient wear-resisting protective coating preparation and application performance evaluation on plane landing gear and wheel and other components. WC-10Co4Cr coating and Cr3C2-25NiCr coating were prepared on 30CrMnSiA steel by HVOF , the OM, SEM, EDS, XRD and other testing methods were used to analyze the composition, microstructure, the conventional friction and wear characterization of the coatings. Finally, the paper emphasis on the friction and wear behavior research of coatings in sand-water environment and systematically studied wear behavior and the influence law of coating on the different service conditions, such as environmental media, friction pair, load and so on. At the same time, the traditional chromium plating was comparative studied, aimed at providing the theory basis of carbide coating replace the chromium plating on surface protection of important parts, which were applied in sand and sea environments, and providing the reference data of the aviation materials coating design and performance improvements.
The results showed that, WC-10Co4Cr coating and Cr3C2-25NiCr coating prepared by optimized HVOF process are dense and uniform,with low porosity. The combine of coating and substrate are very well.The main phases of WC-10Co4Cr coating are WC hard phase and Co binding phase. Cr3C2-25NiCr coating formed mainly by Cr3C2 hard phase and NiCr phase, and certain degree of decarburization of carbide happened during the spraying process. Friction and wear test show that serious adhesion friction occurred between 30CrMnSiA steel and SiC sands, and make the abrasion loss was high, which indicated that wear resistance performance of substrate is insufficient; Surface ceramic coatings deposition can significantly improve the friction and wear resistant properties, due to the high hardness of WC particles and good combination of the Co, WC-10Co4Cr coating show excellent friction and wear resistance performance. While wear resistance performance of Chromium plating is poor, this is because the fatigue wear lead to surface crack and massive broken of layer Dry friction and wear test results showed that, due to the low hardness and severe adhesive in friction of GCrl5, which lead to large material was transferred to the coating surface, and the friction coefficient was in high level. When the coating matched with A1203 friction pair,load factors had small effect on WC-10Co4Cr coating , the friction coefficient remained at about 0.65, the volumetric wear rate less than 3 XO10" mm /N ? m. While due to the surface lubricating film generation and the change of convex body of Cr3C2-25NiCr coating and hard chromium coating , the friction coefficient increased first and then decreased, and wear rate was increased obviously with load increasing.Electrochemical and salt spray test showed that, coatings improved the corrosion potential of the matrix, the corrosion current was increased by 1~2 orders of magnitude. Ceramic coatings showed better corrosion resistance in neutral salt spray test, corrosion resistant level was significantly higher than that of hard chromium plating.
Sand-water environment wear tests showed, water lubrication can significantly decrease the Cr3C2-25NiCr coating's friction coefficient. As the load increased, the friction loss mechanism of coating converts from micro cutting to crack and delamination. Size of Sand medium affects the degree of participation of abrasive during the friction, a certain size sand can form a synergistic wear mechanism with ceramic ball friction pair;while the sand itself was brokered and refined during the wear process.
Key words: WC-10Co4Cr coating, Cr3C2-25NiCr coating, sand-water environment, Friction and wear
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