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庞小通,程序,田象军,汤海波.激光增材制造DD98M高温合金组织及稳定性研究[J].稀有金属材料与工程(英文),2019,48(5):1615~1622.[Pang Xiaotong,Cheng Xu,Tian Xiangjun and Tang Haibo.Microstructures and Long-Term Aging Stability of Nickel-Based Superalloy DD98M by Laser Additive Manufacturing[J].Rare Metal Materials and Engineering,2019,48(5):1615~1622.]
Microstructures and Long-Term Aging Stability of Nickel-Based Superalloy DD98M by Laser Additive Manufacturing
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Received:January 06, 2018  Revised:January 26, 2018
Key words: laser additive manufacturing  nickel-based superalloy  microstructure  long-term aging  γ‘ coarsening
Foundation item:国家863计划(2014AA41701);NSFC-辽宁联合基金(U1508231)
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Pang Xiaotong,Cheng Xu,Tian Xiangjun and Tang Haibo  
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      The DD98M nickel-based superalloy tube is fabricated by using laser additive manufacturing (LAM). The microstructural variations of the as-deposited, solution-aged and long-term aging are studied. The precipitates distribution of deposited and solution-aged alloy were analyzed combining with the study of γ‘ precipitates evolution at 1000 ℃ long-term aging. The results show that the as-deposited microstructure of the alloy mainly consists of epitaxial finer columnar grains with an optimum amount of cubical γ‘ precipitates with around 70 vol. %. No γ-γ‘ eutectic is observed at interdendritic. Rapid solidification during LAM process largely eliminates the segregation of metal elements with an increase of γ‘ precipitates sizes from 210 nm at dendritic arms to 560 nm at interdendritic regions. After solution-aged treatments, γ‘ precipitates (about 370 nm) are uniformly distributed in γ matrix with the sizes distribution fitting the LSW model. During the long-term aging of 500 h at 1000 ℃, no TCP (Topologically Close-Packed) phase exists and the sizes of cubical precipitates have a slight increase. In addition, the micro-hardness of the as-deposited is 442 HV and it will obviously increase to 487 HV after solution-aged heat treatment. Long-term aging reduces around 5.9 % of the maximum micro-hardness.