Microstructure and tensile properties of different hardness regions in as-served P92 steel pipe

doi:10.13251/j.issn.0254-6051.2024.10.024

Abstract

Abstract: Remarkable hardness difference was found in the cross-sectional regions of low outside surface hardness in P92 main steam pipe after serving for 70 000 h. Microscopic and phase analysis, and room-/high-temperature tensile property tests were executed to confirm the microstructure characteristics and mechanical properties of the specimens in different hardness regions. The results show that for the low hardness specimens, widening and decomposing of martensite lathes is severe, lath martensite is gradually transferred to tempered martensite. The M₂₃C₆ and Laves-phase particles precipitated along the prior austenite grain boundaries and martensite lathes are further coarsened and distributed in semi-continuous chains. Meanwhile, the precipitated phase particles dispersively distributed in the martensite and (or) ferrite matrices are also expanded. The room and high temperature tensile strengths of the low hardness specimens are low too, especially, room and high temperature yield strengths of them are lower than the indexes required by the relevant national standards, which could be used for the key mechanical property index in aging state assessment of the as-served P92 main-steam pipe.

Key words: ultra supercritical unit, P92 steel pipe, lath martensite, precipitated phase, hardness, tensile properties

CLC Number:

TG142.1

Li Yong, Ma Jialin, Wang Wanli, Fang Yiming, Zhan Xianqiang, Liu Junjian, Tang Wenming. Microstructure and tensile properties of different hardness regions in as-served P92 steel pipe[J]. Heat Treatment of Metals, 2024, 49(10): 140-147.

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