Effects of Re on microstructure evolution of nickel-based single crystal superalloys
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Effects of Re on microstructure evolution of nickel‑based single crystal superalloys Zhongkui Zhang1,2 · Zhixun Wen1 · Zhufeng Yue1 Received: 29 March 2020 / Accepted: 28 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The high temperature creep and long-term aging tests of the second-generation (DD6) and the third-generation (DD9) single crystal superalloys with different Re contents were carried out. The effects of Re, dislocations, TCP phases and their interaction on creep properties and microstructure evolution were researched. The third-generation single crystal superalloy has the more compact and uniform two-phase structure and the better creep properties. The rafting rate in dendrite is higher than that in interdendrite. The γ’ phases connect into a stripline, the γ phases on the strip line are truncated, and the TCP phase is precipitated along the stripline. The element Re carries out the pipe diffusion and the vacancy diffusion at the high temperature. The TCP phase precipitates in the region with many dislocations and vacancies. Re hinders the movement of dislocations and promote the precipitation of TCP phases. The movement of dislocations promotes the diffusion of Re and the precipitation of TCP phases. TCP phases promote the diffusion of elements and accelerate the rafting of γ’ phases. Keywords Re · Rafting · TCP phase · Dislocation · Single crystal
1 Introduction Nickel-based single crystal superalloys have been widely used in the hot part of the aero-engine because of their excellent high temperature creep resistance and oxidation resistance [1–4]. At present, almost all aero-engines use nickelbased single crystal superalloys as the blade materials, and the nickel-based single crystal superalloys have developed to the fifth generation (TMS-162). For every 55° increase in the temperature bearing capacity of the turbine blade of the aero-engine, the efficiency can be increased by 10% [5]. At present, the aero-engine turbine blade materials in service are mostly the second-generation and the third-generation single crystal superalloys, and the temperature bearing capacity of each generation is about 30° higher than that of the previous [2, 6]. Conducting researches on high-temperature properties and basic theory of nickel-based single * Zhongkui Zhang [email protected] 1
School of Mechanics, Civil Engineering and Architecture, Northwestern Polytechnical University, Xi’an 710072, People’s Republic of China
Xi’an University of Posts and Telecommunications, Xi’an 710121, People’s Republic of China
2
crystal superalloys to accelerate the upgrading of singlecrystal materials has great significance to the development of the aviation industry. In the development of single crystal superalloys, the refractory element Re has the greatest effect on improving the mechanical properties [7]. 3% Re and 6% Re are almost the main features and differences of the second-generation and the third-generation single crystal superalloys. The addition of Re can significantly
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