Evaluation of adhesion quality of oxide scale on low carbon steel at high temperature using a laser spallation technique

Abstract

This study aims to evaluate adhesion quality of oxide scale on low carbon steel plate at high temperature. The scratch test, indentation test and pull-out test are generally adopted to evaluate the adhesion quality of thin films. However, these methods requires contact between a probe and a specimen, and are not allowed to perform at high temperature. Since a laser spallation technique is a non-contact measuring method which produces tensile stress acting on an interface by ultrasonic wave, the method enables us to evaluate the adhesion quality at high temperature. In this study, adhesion quality of the oxide scale on low carbon steel was attempted to evaluate at room temperature and up to 200 °C with the laser spallation technique. The exfoliation which was induced by the laser spallation technique can be identified by change in correlation coefficient for a series of the waveform obtained at each energy of incident YAG laser. Tensile stress acting on interface was estimated from stress distribution of the wave propagating through the interface calculated with a numerical simulation. As a result, it was confirmed that the adhesion quality of the oxide scale increased with testing temperature. It may be because the residual stress which acts on an oxide scale/substrate interface decreased with temperature.

Keywords

• laser spallation technique
• oxide scale
• adhesion quality
• exfoliation detection