超超临界机组GH4169螺栓高温运行后显微组织与力学性能的研究

Study on Microstructure and Mechanical Properties of GH4169 Bolt in Ultra-Supercritical Unit after High Temperature Operation

从某超超临界1000MW机组服役约18000 h的镍基高温合金GH4169螺栓的螺纹处、光杆处分别取样,进行显微组织、室温力学性能、高温力学性能以及高温持久试验。结果表明:服役后的GH4169螺栓的金相组织稳定,为基体γ相和γ"、γ’强化相,且不同部位的γ"、γ’强化相的形态、大小和含量基本相同;服役后的GH4169螺栓的布氏硬度符合国家标准要求,且横截面方向不同区域的硬度较均匀;服役后的GH4169螺栓的室温拉伸、高温拉伸和室温冲击性能各项指标均满足标准要求,且断口均表现出韧性断裂特征;在566℃下,随着试验应力的降低,服役后的GH4169螺栓试样的断裂时间呈增长趋势,拟合曲线外推出的10万小时持久强度约为662 MPa。

The microstructure, mechanical properties at room temperature & high temperature and stress-rupture test in tension at high temperature were performed on the thread sample, rod samples of a nickel-based superalloy GH4169 bolt which has been serviced in an ultra-supercritical 1000MW unit for about 18 000 h. The results show that the metallographic structure of the GH4169 bolt after service is stable, and it is the matrix γ phase, γ " and γ’ strengthening phases, and the morphology, size and content of γ" and γ’ strengthening phases are basically the same in different parts. The Brinell hardness of the GH4169 bolts after service still meets the national standard requirements, and the hardness values in the cross-section direction are relatively uniform in different regions;the room temperature tensile, high temperature tensile and room temperature impact properties of the GH4169 bolts after service meet the standard requirements well, and the fractures show ductile fracture characteristics;the rupture time of GH4169 bolts specimens after service at 566 ℃ shows an increasing trend as the stress reduces, and the estimated rupture strength for 100000 h is about 622 MPa by fitting curve and extrapolation.