Damage Evaluation in High Temperature Stainless Steel Components Using Non-Destructive Techniques

AISI type 310 stainless steel is currently in demand for the biomass gasifier plants in India as the main structural material. During operation of the plant this steel undergoes temperature as high as 1373 K and variation in temperature and stress. In this work, we have received virgin and service exposed sample cut near the weld failure region of AISI type 304 SS suitably prepared and used for ultrasonic velocity measurements, acoustic emission testing (AET) and photoacoustic (PA) measurements on the virgin and service exposed specimens of AISI type 310 high temperatures steel with the aim to use the outcome of the study to increase the life cycle of the steel and hence the biomass plant. Acoustic emission (AE) test results indicate that as compared to the virgin specimens, strength increases and ductility decreases for the service-exposed specimens. AE generated is also higher for the service-exposed specimens as compared to the virgin specimens. Ultrasonic velocity measurements show comparatively higher velocity in service exposed specimen than in virgin specimen and the hardness measurements show opposite trend to that of ultrasonic measurements. The studies clearly indicate the immense possibility of the applying NDT techniques in assessing the service degradation taking place during the gasifier. In addition, Metallography and Photoacoustics (PA) measurements were also conducted on the specimens. It is found that PA measurements results found to correlate well with the above measurement results.