Detection of Hydrogen Assisted Cracking Susceptibility in Modified 9Cr-1Mo Steel Welds by Acoustic Emission Technique

Abstract

Assessment of hydrogen assisted cracking susceptibility for high chromium steel weldments is extremely important to avoid damage and sudden failure of components used in fossil power plants and nuclear reactors. Acoustic emission is a novel non-destructive technique that can be successfully employed to detect crack initiation and propagation behavior of the welds during Gap – Bead on Plate test, Y-Groove and Implant test of Modified 9Cr-1Mo steel plates. The diffusible hydrogen content of AWS E9018-B9 electrode under different preheating-post heating conditions is determined by gas chromatography technique. It is observed that the percentage of crack, as determined from G-Bop, Y-Groove tests decreases with increase in preheat, post heat temperature from 100° to 150°C and no cracking is optimized at 200°C preheat- no post heating conditions. Lower critical stress calculated based on implant test data is 328 MPa for the steel welded with 200°C preheat. The diffusible hydrogen content (3.71 ml/100 gm of weld metal) is also lowest for similar welding condition. Acoustic emission time domain analysis of cumulative count shows peak shifting of waves, which confirms the crack initiation and propagation behavior.