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Study on Mechanical and Microstructural Evolution of P92 Pipes During Long-Time Operation
Liying Tang1, Zheyi Yang1, Xionghua Cui1
1Xi'an Thermal Power Research Institute Co., Ltd., Xi'an 710054, China.
Materials (Basel, Switzerland)
|October 26, 2024
Summary
Long-term operation under stress degrades P92 steel steam pipes, reducing mechanical properties and accelerating microstructure aging. Residual life evaluation requires considering operational stress effects, as some properties are insensitive to aging.
Area of Science:
- Materials Science
- Mechanical Engineering
- Metallurgy
Background:
- P92 steel is crucial for ultra-supercritical power plants.
- Understanding long-term operational effects on P92 steel is vital for plant safety and efficiency.
Purpose of the Study:
- To investigate the mechanical properties and microstructure evolution of P92 steel after long-term service under stress.
- To assess the impact of operational stress on material aging and performance degradation.
Main Methods:
- Samples from operated P92 main steam pipes with varying service durations and stresses were analyzed.
- Mechanical property testing included tensile strength, impact, hardness, and creep resistance.
- Microstructure analysis was performed using optical metallography and transmission electron microscopy (TEM).
Main Results:
- Circumferential stress significantly accelerates creep life consumption and degrades mechanical properties of P92 steel.
- Tensile strength (Rp0.2 and Rm) decreased with increased service time and stress.
- Impact absorption energy and hardness showed non-monotonic relationships with operating time, indicating insensitivity to stress-induced aging.
Conclusions:
- Operational stress is a key factor in the degradation and aging of P92 steel steam pipes.
- Tensile strength is a potential indicator for residual life evaluation.
- TEM is essential for a thorough assessment of stress-induced aging, as optical metallography is insufficient.
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