Long-term service induced mechanical properties change of hot-end welding metals in a retired CrMoV bainitic gas turbine rotor

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2022-01, Vol.833, p.142323, Article 142323
• Main Authors: Rui, Shao-Shi, Han, Qi-Nan, Wang, Xue, Zhao, Jia-Min, Cai, Zhipeng, Du, Dong, Shi, Hui-Ji
• Format: Article
• Language: English
• Subjects: Anelastic relaxation; Crack propagation; Creep strength; Dislocation density; Elastic modulus; Fatigue failure; Gas turbines; High temperature; Mechanical properties; Modulus of elasticity; Retired rotor; Room temperature; Rotors; Welding; Welding metal
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2021.142323

This research focused on evaluating the mechanical properties change of Welding Metals (WMs) at the turbine-end (hot-end, working beyond 500 °C) of a retired CrMoV bainitic gas turbine rotor serving over 14 years, by comparison to those WMs at the compressor-end (cold-end, working below 300 °C). After long-term service, the room-temperature elastic modulus and the bainitic microstructure of hot-end WMs stayed almost the same as those of cold-end WMs, but the high-temperature elastic modulus and the dislocations density of the former became higher than those of the latter. The above change, especially the change of high-temperature elastic modulus produced significant influences on the tensile, fatigue and creep behaviors of hot-end WMs, which further led to a higher tensile and creep strength but a lower ductility, as well as a better fatigue crack propagation resistance under high-temperature condition. A correlation between the high-temperature elastic modulus change and the tensile/fatigue/creep behaviors change was established for hot-end WMs based on mechanics modelling, which provided a feasible way to monitor the rotor properties change. •Long-term service raised the activation energy for anelastic relaxation of hot-end welding metals.•High-temperature elastic modulus of hot-end welding metals with less anelasticity became higher.•Higher elastic modulus improves tensile/creep strength but reduces ductility at high-temperature.•Higher elastic modulus increases the resistance to fatigue crack propagation at high-temperature.