Journal of Pure and Applied Ultrasonics

S. Raja Karthihan ¹, T. M. Haridasan ², P. Palanichamy ³, C. K. Mukopadhyay ³, P. Kalyanasundaram ³,

Affiliations
1 Department of Physics, Sethu Institute of Technology, Kariapatti-626106, IN
2 School of Energy, Madurai Kamaraj University, Madurai-625021, IN
3 Division for PIE & NDT Development, Indira Gandhi Center for Atomic Research, Kalpakkam-603102, IN

Abstract

A biomass gasifier was in operation for sometime and later failed near the weld portion. A portion of the sample near the failed region was cut and used for this investigation. Study based on ultrasonic velocity measurements, metallography and X-ray diffraction was carried out at different portions of samples of stainless steel used in the biomass gasifier. Precise ultrasonic velocity measurements were performed by pulse echo method using cross correlation technique. Longitudinal ultrasonic wave generating probes of 5 and 20 MHz were used. It is found that there is an increase in ultrasonic velocity in samples obtained from the exposed portion as compared to the virgin samples. Metallographic studies revealed that there is a microstructural reformation taking place due to prolonged temperature treatment at the regions away from the failed portion. Very near the failed portion, there is intergranular type crack propagation as a result of partial sensitization and embrittlement. X-ray diffraction study is in support of the metallographic observations. The increase in ultrasonic velocities in service exposed specimen with and without intergranular cracks was attributed to the continuous changes taking place in the microstructures. It is suggested that periodic monitoring of the critical parts especially the combustion zone by NDE techniques would help avoid premature failure of the biomass gasifier plant.

Keywords

Ultrasonic Measurements, Biomass Gasifier, AISI Type 310 Stainless Steel, Microstructures, Characterization.

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S. Raja Karthihan ¹, T. M. Haridasan ², C. Sanjeevi Raja ³, P. Palanichamy ⁴, C. K. Mukhopadhyay ⁴, P. Kalyanasundaram ⁴

Affiliations
1 Department of Physics, Thiagarajar College, Madurai-625009, IN
2 School of Energy, Madurai Kamaraj University, Madurai-625021, IN
3 Department of Physics, Alagappa University, Karaikudi-623001, IN
4 Non Destructive Evaluation Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, IN

Abstract

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.

Keywords

Biomass Gasifier, High Temperature Steel, Ultrasonic Nondestructive Testing.

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