Li Yi, Sun Chao, Liu Kai, Xu Tong, He Binbin
Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
China Special Equipment Inspection and Research Institute, Beijing 100029, China.
Materials (Basel). 2022 Jul 13;15(14):4865. doi: 10.3390/ma15144865.
The present paper investigates the use of the magnetic hysteresis loop technique to nondestructively evaluate microstructural degradation in heat-resistant martensitic (HRM) steels. The degradation impairs the safe operation of thermal power plants and it is thus essential to periodically assess it using nondestructive evaluation (NDE) techniques. In this contribution, HRM steels are thermally aged up to 16,000 h at 675 °C to simulate the microstructural degradation, then the changes in the magnetic coercivity, hardness, and microstructure are systematically characterized and the relations between them are determined. Both coercivity and hardness decrease with thermal aging duration, which can be interpreted in terms of the microstructure parameters' evolution based on the pinning of crystal defects on domain walls and dislocations. Coercivity and hardness share the same softening trend with aging time, and good linear relations between coercivity, hardness, and microstructure parameters are found. These results provide a key to understanding the magnetic parameter evolution in HRM steels and suggest the possibility of using magnetic technologies for the NDE of microstructure degradation in thermal power plants.
本文研究了利用磁滞回线技术对耐热马氏体（HRM）钢的微观结构退化进行无损评估。这种退化会损害火力发电厂的安全运行，因此使用无损评估（NDE）技术定期对其进行评估至关重要。在本研究中，将HRM钢在675℃下热时效长达16000小时以模拟微观结构退化，然后系统地表征磁矫顽力、硬度和微观结构的变化，并确定它们之间的关系。矫顽力和硬度均随热时效时间的延长而降低，这可以根据基于晶界和位错上晶体缺陷钉扎的微观结构参数演变来解释。矫顽力和硬度随时效时间呈现相同的软化趋势，并且发现矫顽力、硬度和微观结构参数之间存在良好的线性关系。这些结果为理解HRM钢中磁参数的演变提供了关键，并表明了利用磁技术对火力发电厂微观结构退化进行无损检测的可能性。
