Evaluation of the heat-affected zone (HAZ) of a weld joint using nonlinear Rayleigh waves

Nonlinear ultrasound (NLU) has been shown to be sensitive to microstructural features including precipitates and dislocations. The heat-affected zone (HAZ) of welded austenitic stainless steels can be susceptible to intergranular stress corrosion cracking (IGSCC). This research uses NLU to evaluate the microstructure of the HAZ with an emphasis on dislocations, precipitates, grain size/morphology and sensitization, which is the formation of chromium carbide precipitates at the grain boundaries. The results show that there is a large increase in the measured acoustic nonlinearity parameter in the vicinity of the HAZ, which can be used to monitor changes in microstructure such as sensitization.