Composite coating is a kind of high temperature and oxidation resistant coating used in combination with ceramic coating and glass coating. It can not only work in high temperature environment, but also has the ability of microcrack self-healing of coating. MoSi or Si is usually selected as the transition layer or bonding layer of the antioxidant coating to relieve the thermal stress between the coating and the substrate, and the outer sealing layer is generally selected as high temperature resistant glass or high temperature oxide. For example, the MoSi diffusion layer/CDd-Mosi barrier layer/Mulmulite seal coating IR-Si/dense Ir barrier layer /SrZrO studied by foreign scholar (Al0;) Si (CVD) /Ir (CVD or plasma spraying) /Y203 (plasma spraying) composite coating group prepared by Scholars 0. Si/Y SiO prepared.; The coating has better oxidation resistance at high temperature. In particular, the Ir barrier layer /SrZrO3(Al2O3) composite high temperature antioxidant coating also has the antioxidant protection ability at 1750℃ for a long time. In addition, the composite coating of IR-Si mixed layer/dense Ir barrier SrZrO3(Al2O3) corrosion resistant layer prepared by scholar et al has an oxidation resistance time of only 21min at 1950 ℃. The main reason is that the bonding strength between the I barrier layer prepared by PVD method and the Ir-Ta layer is poor, leading to cracks. Meanwhile, the excessive crystallization of SrZrO3 leads to defects, leading to decreased oxidation resistance at high temperature. The Ir/ZrO/Y of Ti (CVD) /Ir (CVD or plasma spraying) /Y203 (plasma spraying) composite anti-oxidation coating developed by scholar., when oxidized for 25min at 1960℃, the oxidation weight gain was 6.4%. After the coating was oxidized at 1850℃ for 35 min, the oxidation weight gain was 4.1%. In the early 1990s, the Russian composite material research and production consortium developed MoSi2+HaSi composite protective coating, which uses the preparation process of slurry spraying a high temperature melting - encasing silication coating high temperature oxidation resistance at 1800 ℃, the oxidation resistance time reached 100h with a long time of antioxidant protection ability. At present, the substrate is first prepared on the surface of Ta-12W alloy and then sintered. After the preparation surface is sintered at high temperature, the silicon coating is formed on the surface of the alloy. The oxidation resistance time of the coating at 1800℃ reaches 9h and the thermal shock life from room temperature to 1800℃ is 151 times.
The inevitable thermal expansion difference between tantalum and tantalum alloy material substrate and coating material is also the main cause of coating cracks. Tantalum and tantalum alloy material coatings can eliminate coating cracks by preparing the above-mentioned sealing layer and gradient coating. The gradient coating can make the concentration of two phases between the coating and the substrate as well as the composition of the polyphase coating present a continuous distribution, eliminating the stress between all surfaces, and there is no crack on the surface, finally achieving the purpose of oxidation resistance at high temperature.
