Post-weld heat treatment cracking susceptibility of T23 weld metals for fossil fuel applications

The post-weld heat treatment (PWHT) cracking susceptibilities of 123 steel welded with four types of filler metals were evaluated by measuring the stress-rupture parameters (SRP), which are based on both the stress-rupture strength and the stress-rupture ductility. Post-weld heat treatment cracking tests were performed on T23 weld metals using a Gleeble system at temperatures of 650-750 degrees C and at stress levels of 100-500 MPa. The results showed that the weld metals with a higher SRP exhibited improved rupture stress and ductility. In addition to measuring the SRP values, the PWHT cracking susceptibility of each weld metal was compared and discussed with respect to the fracture morphology, the solute segregation at the grain boundary, the precipitation behavior, and the denuded zone formed during treatment (which can affect the stress-rupture parameter). It was found that solute segregation was severely deleterious and resulted in lower stress-rupture parameters. In addition, Mo was found to interrupt W-depletion adjacent to M3C or M23C6 particles, retarding and weakening of the denuded zone along the grain boundaries. (C) 2011 Elsevier Ltd. All rights reserved.