Research On Processing And Properties Of Anti-corrosion And Wear Resistance Coating On TC18 Alloy Surface

TC18 alloys have been applied to aircraft landing gear, due to their good properties including low density, high specific strength and so on. These alloys confront corrosion and abrasion problems like other titanium alloys. In this article, the author design two kinds of coatings, Al2O3 coating and WC-Co coating, to improve their anti-corrosion and wear-resistance properties. Firstly, the substrate needed to be suitably pre-treated by acid pickling and chemical passivation. Secondly, the composition of these coatings was optimized by orthogonal experiment methods. The curing process parameter of coatings was analyzed by DSC and IR. Thirdly, the physical mechanical properties were characterized according to relative standards, especially in anti-corrosion and wear resistance properties.The results showed that the adhesion and anti-corrosion properties were enhanced by pre-treated technique. For Al2O3 coating, the proportion of ingredients was 800 mesh Al2O3 : 1500 mesh Al2O3 : coupling agent = 24%:22%:2%, the rest was epoxy resin and polyamid(1:1.05). For WC-Co coating, the proportion of ingredients was WC-Co : 800 mesh Al2O3 : coupling agent = 29%:6%:2%, the rest was epoxy resin and polyamid(1:1.05). Under 120℃ for preservation 2h, the colour, thickness, adhesion, and impact toughness of the uniform and compact coatings were all up to standard.The electrochemical test was conducted in 3.5wt%Na Cl solution. The result demonstrated that the coating had a higher corrosion potential and lower corrosion current than the substrate. The protection ratio of Al2O3 coating and WC-Co coating is 98.8% and 98.3%, respectively. As the immersing time growing, the capacitive reactance arc amplitude of the coatings greatly decreased. Up to 25 days, the decreasing range begin to minish. After 750 h neutral salt spray test, the substrate shows serious corrosion behavior while the surface of coatings occurred no apparently change. The moisture and heating test was also conducted for 750 h, and the coatings appeared lacking glue phenomenon. In room temperature, the coatings have a lower friction coefficient fluctuation range, smaller wear weightlessness and lower wear rate both at low rotation speed and load as well as high rotation speed and load compared with the substrate, which implies that the coating have excellent wear resistance. All the evidences show that the coatings have excellent wear performance and corrosion resistance, and Al2O3 coating is better than WC-Co coating.