| Titanium alloy, due to its high specific strength and excellent anti-corrosion characteristics of the marine environment, has been widely used in aerospace and other fields. But the high temperature oxidation resistance of the titanium alloy is poor and easy to form titanium fire burning, which lead it can only be applied at low temperatures. However, some military special titanium parts used at high temperatures required, only a limited improvement from temperature titanium alloy matrix composition, the use of surface coating protection is an affordable way. In this paper, the most widely used titanium alloy of TC4(Ti6A14V) alloy as the research object, the inner dense layer in micro-arc oxidation (MAO) coating was prepared as the anti-oxidation layer and the outer porous layer as the adhesive layer to the plasma spraying YSZ layer, which constitutes a new anti-oxidation and insulation coating systems to improve the antioxidant and insulation property of the TC4 alloy, through this process, to improve the using temperature of titanium alloy and solve some particular conditions of the requirements of titanium alloy puzzle is extremely important theoretical and practical value.Firstly, a series of studies were carried to obtain the micro-arc oxidation coating which owns the most excellent antioxidant properties. Single phosphate was chosed as the electrolyte, orthogonal experiment was carried out to optimize the experimental parameter in phosphate solution (Voltage, Time, electrolyte concentration) to get coating with good oxidation resistance and structure. Effects of various parameters on the coating thickness and oxidation resistance property were discussed. The oxidation kinetics behavior of micro-arc oxidation coating was researched, the micro-arc oxidation coating growth model on titanium surface in phosphate electrolyte was established. The growth mechanism of micro-arc oxidation coating on titanium surface got enriched. The second function mathematical model between preparation parameters of micro-arc oxidation coating in phosphate electrolyte and weight gain by oxidation (high temperature oxidation resistance) was fitted by regression analysis.Under the optimized experimental parameter, micro-ZrO2 and micro-Al2O3 ceramic particles were added in soluction to prepare ZrO2/ZrTiO4 and Al2TiO5 composite coating respectively. Affect on coating structure, surface roughness, oxidation resistance and thermal shock resistance, abrasion resistance and the substrate bonding strength by added ceramic particle was systematic studied, oxidation kinetics behavior of coating prepared within and without particle was comparised. The oxidation kinetics were fitted in Wagner theory to foreast the oxidation of samples in longer. The results showed that:the composite coating than a single micro-arc oxidation coating without particle has a more dense coating structure; more excellent high temperature oxidation and thermal shock properties; better wear characteristics and a higher coating layer adhesion. The added in ceramic particle was inhaled to become solidified molten ceramic core to accelerate the solidification process, reduce the number of micro-arc hole; after the ceramic particle fused into the ceramic coating due to the volume effect caused denser, reflecting more excellent performance.The YSZ coating was prepared by plasma spraying on the modified with ceramic particles MAO coating. The structure, high temperature oxidation resistance, thermal insulation of TMPAl-YSZ and traditional MCrAlY-YSZ composite coating were systematic researched. The results showed that micro-arc oxidation coating and YSZ coating closely integrated combination of high strength; theTMPAl-YSZ composite coating has better oxidation resistance than conventional MCrAlY-YSZ coating at 700℃ for 200h and no mutual elements diffusion between MAO coating and the substrate. The insulation test, calculation of the one-dimensional transient heat conduction differential equations at the third boundary condition and Ansys software for one-dimensional thermal analysis were carried to characterize the thermal insulation properties of the composite coatings. Micro-arc oxidation coating as an oxygen barrier layer has good oxidation resistance at high temperature, no element diffusion between coating and substrate at high temperature:the significant "crater" structural characteristic on surface helps its riveting between MAO coating and plasma spraying YSZ coating, which helps to realize the anti-oxidation and insulating protection for titanium alloy based on the no affect on physical properties. |
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