Type IV Creep Cracking of Welded Joints of P92 Steel After Long - term Service

CHE Chang; ZHAO Yulong; YU Jianming; GAO Kai; XIANG Yong; LIAO Xiaowei

doi:10.7512/j.issn.1001-2303.2025.06.05

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Type IV Creep Cracking of Welded Joints of P92 Steel After Long - term Service
Vol. 55, Issue 6, Pages: 31-41(2025)
Received：23 February 2025，

Revised：06 March 2025，

Published：20 June 2025
DOI： 10.7512/j.issn.1001-2303.2025.06.05
稿件说明：

移动端阅览

车畅，赵玉隆，于建明，等.长期服役P92钢焊接接头IV型蠕变开裂研究［J］.电焊机，2025，55（6）：31-41. DOI： 10.7512/j.issn.1001-2303.2025.06.05.

CHE Chang, ZHAO Yulong, YU Jianming, et al.Type IV Creep Cracking of Welded Joints of P92 Steel After Long - term Service[J].Electric Welding Machine, 2025, 55(6): 31-41. DOI： 10.7512/j.issn.1001-2303.2025.06.05.

摘要

P92钢广泛应用于超超临界机组高温部件，其焊接接头性能关乎机组安全稳定运行。然而，长期高温服役下P92钢焊接接头易出现IV型蠕变开裂问题，现有研究多采用加速蠕变试验，缺乏对实际长期服役焊接接头的研究。以国内某电厂服役70 000 h的主蒸汽管道P92钢焊接接头为研究对象，运用真空光谱仪分析化学成分，借助扫描电镜（SEM）、能谱仪（EDS）和电子背散射衍射（EBSD）观察显微组织并测量维氏硬度。研究结果表明，细晶区是IV型失效的主要区域，存在大量蠕变孔洞和微裂纹，其附近聚

集着大尺寸的Laves和M

相，这两种相的粗化促进了蠕变孔洞的成核和生长，还削弱了弥散强化和固溶强化。此外，焊接接头IV型裂纹侧硬度呈梯度分布，细晶区硬度最低值为150 HV，平均硬度值为175 HV，软化程度高。该研究针对实际长期服役的P92钢焊接接头开展全面研究，为准确掌握其IV型蠕变开裂机制提供了重要依据，有助于电力行业制定更合理的检测、维护策略，保障机组安全稳定运行，在电力设备材料性能研究领域具有重要的推广应用价值。

Abstract

P92 steel has found extensive applications in high - temperature components of ultra - supercritical power generation units. The integrity and performance of its welded joints are of utmost significance for the reliable and stable operation of these power - generating facilities. Nevertheless

during long - term exposure to high - temperature service conditions

the welded joints of P92 steel are highly susceptible to Type IV creep cracking

which poses a significant threat to the safety and reliability of the units. Existing research efforts have predominantly relied on accelerated creep tests

leaving a notable gap in the understanding of the actual long - term service behavior of welded joints.In this study

the welded joints of P92 steel in the main steam pipeline of a domestic power plant with 70

000 hours of service were selected as the research subject. The chemical composition was precisely analyzed using a vacuum spectrometer. The microstructure was comprehensively characterized by means of a scanning electron microscope (SEM)

an energy - dispersive spectrometer (EDS) and electron backscatter diffraction (EBSD). Moreover

the Vickers hardness was accurately measured to evaluate the mechanical properties of different regions.The experimental results revealed that the fine - grained zone served as the primary location for Type IV failure. This region was filled with numerous creep pores and micro - cracks. Large - sized Laves and M23C6 phases were prominently aggregated adjacent to the fine - grained zone. The coarsening of these two phases not only significantly promoted the nucleation and growth of creep pores but also effectively diminished the dispersion strengthening and solid - solution strengthening effects. Additionally

the hardness distribution on the Type IV crack - affected side of the welded joint exhibited a distinct gradient. The minimum hardness value within the fine - grained zone was measured at 150 HV

with an average value of 175 HV

indicating a substantial degree of softening.This research conducted a comprehensive and in - depth investigation into the long - term service behavior of P92 steel welded joints. The findings provided a crucial foundation for accurately deciphering the Type IV creep cracking mechanism. Such insights are instrumental for the power industry to formulate more scientific and reasonable inspection and maintenance strategies

thereby ensuring the safe and stable operation of power generation units. The research outcomes hold great promise for wide - scale application and promotion in the field of power equipment material performance research.

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