Preparation Of CoCrAlTaY Superalloy Powder By Vacuum Atomization And Its Oxidation Resistance

Cobalt base superalloy has good oxidation resistance property in high temperature and strong cohesiveness which is beneficial to extending the life of coatings. Currently, Ta segregation problem usually exist in CoCrAlTaY superalloy powder and coatings that seriously reduced the high temperature oxidation resistance property of coatings the life of the coating.This paper focuses on preparing CoCrAlTaY superalloy powder using optimized parameters of vacuum atomization process and research the oxidation resistance property of thermal barrier coatings (TBC) with CoCrAlTaY bond coats. In addtion, related features of CoCrAlTaY superalloy powder has been investigated. The research contents and results for this study are as follows:To prepare high quality CoCrAlTaY powder and eliminate Ta segregation problem, some parameters such as melting temperature, atomization temperature,atomization pressure and the diameter of draft tube has been optimized and using CoTa alloy as experiment material. Studies on related features of CoCrAlTaY superalloy powder have indicated that:the CoCrAlTaY superalloy powder with CoTa alloy as raw material has more uniform microstructure and the white block(Ta) has almost disappeared; the powder is mainly composed of y’, CoAl and TaC phase; Ta exists in the form of Co3Ta and TaC, and the rest of Ta dispersed in the powder.The factors influencing the high temperature oxidation resistance and life of TBC with CoCrAlTaY bond coating have been studied which involve temperature and oxidation conditions, water vapor atmosphere and the chemical composition of bond coating etc. The results show that:The life of TBC has a larger difference after oxidation at 1000 ℃ than 1050 ℃ because of the 50 ℃ higher temperature might promoting the oxide growth and elements inter-diffusion. Due to the stress in cyclic oxidation condition, the growth and propagation of cracks could become rapid and simpleness which lead to shorter life TBC. Water vapor environment has bad effec on TBC life. The life of the EB-PVD TBC with CoCrAlTaY bond-coat was longer than that with NiCoCrAlYTa bond-coat after cyclic oxidation at 1100 ℃. The low CTE of Co base bond-coat could contribute to the longer lifetime of the TBC systems compared to the Ni base bondcoats.