Microstructure and mechanical properties of long-term high temperature serviced superalloy GH4145 bolt

doi:10.13251/j.issn.0254-6051.2025.03.030

Abstract

Abstract: A comparative study between GH4145 alloy bolt served for about 60 000 h at 537 ℃ and standard heat treated (unserved) GH4145 alloy bars was carried out. The microstructure and precipitated phase characteristics of the both specimens were observed and analyzed by means of optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The Brinell hardness, tensile properties at room temperature and high temperature, impact properties and endurance properties were tested. The results show that the microstructure of both specimens is typical austenite, with twins and carbides in the grains. The average grain size of the serviced bolt is not significantly larger than that of the unserviced bar. The size and volume fraction of γ′ phase at the thread and polished rod of the serviced bolt are basically the same. The size and the volume fraction of γ′ phase in the serviced bolt are larger and higher than those in the unserviced state. In terms of mechanical properties, in addition to the high hardness value at the polished rod of the service bolt, the room temperature tensile and high temperature durability properties of the serviced bolt and the unserviced bolt both meet the standard requirements. The yield strength at the polished rod is higher than that at the thread, and the hardness and strength of the serviced bolt are higher than those of the unserviced state.

Key words: superalloy GH4145, high temperature serviced bolt, microstructure, mechanical properties

CLC Number:

TG156.9

Zhou Hao, Du Haojie, Zeng Yanping, Guo Derui, Li Weili, Ma Zhibao, Wang Qingfeng, Li Jingxin. Microstructure and mechanical properties of long-term high temperature serviced superalloy GH4145 bolt[J]. Heat Treatment of Metals, 2025, 50(3): 189-195.

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