A small punch test method,microhardness method,and metallographic analysis method were employed to investigate the 15CrMo heat-resistant steel pipe material under conditions of high temperature and high pressure(260℃±20℃ and 27 MPa)following a prolonged service period of 115000 hours.It was determined that the reduction rates of the maximum load and the maximum displacement of 15CrMo heat-resistant steel after long service were 5.6%and 5.89%,respectively.The microhardness analysis indicates that there is an 8%increase in microhardness within 1 mm of the inner surface,which is attributed to the long-term high-temperature oxidation damage experienced by the inner surface.Furthermore,microstructure analysis revealed that high-temperature oxidation corrosion resulted in the shedding of grains on the inner wall of the long-term serviced pipeline,which was prone to microcracks,ultimately leading to pipeline cracking.The results of this study indicate that the damage to 15CrMo heat-resistant steel at elevated temperatures over an extended service period is limited.The material retains its strength and plastic properties,with no significant deterioration in mechanical properties or embrittlement.However,the high-temperature oxidation damage observed in the inner wall of the pipeline should be a concern.This study provides a reference for the structural integrity evaluation of high-temperature pipelines in power plants.
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