Failure Analysis and Magnetic Evaluation of Tertiary Superheater Tube Used in Gas-Fired Boiler

Magnetic evaluation of accelerated aging degradation on 2.25Cr-1Mo steel with martensitic and bainitic microstructure

“…Energy dispersive x-ray (EDX) analysis was carried out for the evaluation of chemical composition of the carbides at various stages of ageing. MHL measurements were conducted on both surfaces of the steels using a portable magnetic NDE tester; MagStar with the applied field and frequency was the same as reported earlier (18). The portable equipment can be taken to the site, and using surface probes, the microstructural modifications can be monitored to assess the health of the components.…”

“…Hence, a large magnetizing force is required to remove the residual field, resulting in a higher coercive force. A decrease in pinning density in terms of microstructural degradation such as grain growth (which reduces grain boundary area), lath broadening (which reduces lath boundary area), spheroidization (which reduces the surface area of the carbides), coarsening of precipitates in the expenses of a large number of finer precipitates (which decreases the number density of precipitates), and relaxation of compressive residual stress (which reduces the strain field) decreases the coercive force in ferromagnetic materials such as steels (10)(11)(12)(13)(14)(15)(16)(17)(18).…”

“…The development of suitable NDE techniques for monitoring the health of the components for precise evaluation of microstructure and mechanical properties is highly desirable. Magneticbased NDE techniques are in growing demand for the common pinning sites for the magnetic domain wall motion and dislocation motion in steels (9)(10)(11)(12)(13)(14)(15)(16)(17)(18). However, the sensitivity of the different magnetic parameters to various micro-constituents makes the technique complex to evaluate.…”