Long-term stability of laser processed reference samples for grinding burn detection with Barkhausen noise

Barkhausen noise (BN) is industrially relevant quality control method which is used for process control of i.e. grinding. Similarly to any non-destructive testing measurement also BN measurement requires reference samples. Previously, laser irradiation method with optical pyrometer control was found to be an effective method to produce controlled and reproducible heating effect to metal surfaces. In this study, the long-term stability and changes in the laser processed reference samples were inspected. During the long-term stability survey, certain guidelines which are helpful for preparing the reference samples and evaluating the long-term usability of them were noticed. It was found that the sample initial structure should be as stable as possible prior laser processing. One key finding was that carburized, case-hardened samples are unstable for reference samples since the retained austenite decomposition over time may affect the BN signal levels making these samples unsuitable for reliable long-term use. In addition, the laser irradiation temperature needs to be optimized to produce significant change to the BN signal level. However, too high temperature would produce too altered area compared to production which might observe more easily mechanical effects from the dynamical use with BN sensors. • Sample initial structure prior laser processing should be as stable as possible • Laser temperature should be optimized to produce meaningful change to the BN signal level • Too high temperature produces altered area which observe more easily mechanical effects from the dynamical use