Microstructure and properties of P91 steel pipe after long term high temperature service

doi:10.13251/j.issn.0254-6051.2024.09.007

Abstract

Abstract: Rated operating temperature of the P91 steel pipe was 541 ℃, the operating pressure was 17.5 MPa, and the specification was ϕ194 mm×25 mm. After about 78 000 h of service, its hardness was below the lower limit of the standard. Microstructure and properties of the P91 steel pipes used in a subcritical boiler after long-term service was investigated by means of metallographic, transmission electron microscopy, chemical phase analysis, creep-rupture properties and other test methods, respectively. The results show that the widening of martensite laths and the coarsening of the M₂₃C₆ phase at the grain boundaries of the P91 steel pipes after long-term high-temperature service are the main reasons for the decrease in high-temperature strength. Specimens were taken from the P91 steel tubes for endurance testing, resulting in creep rupture strength value of 72 MPa for 100 000 h of extrapolation at 566 ℃. Data can be used as the reference for the assessment of the creep life of the P91 steel.

Key words: P91 steel pipe, long-term high temperature service, microstructure, properties

CLC Number:

TG142.1

Zhang Yingwei, Bai Jianqiang, Bai Zhanqiao, Li Weili, Shen Kang, Dong Shuqing. Microstructure and properties of P91 steel pipe after long term high temperature service[J]. Heat Treatment of Metals, 2024, 49(9): 43-46.

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