Modelling of the transient thermal field in laser surface treatment test

In order to develop adequate predictive models of the laser heat treating process in the recent past, the laser surface treatment (LST) test was proposed to relate the obtained microstructure to the known thermal cycle undergone by the material. One of the flat end surfaces of a cylindrical steel rod is exposed to a laser beam. As a consequence the material undergoes different thermal cycles and different microstructure transformations due to the heating effect of the laser beam that it propagates inside the material. The paper presents a thermal model that can be used in the LST test to predict the thermal field inside the rod exposed to the laser beam. The model describes the thermal field generated by a uniform and time-dependent heat source, and also accounts for the convection losses that are due to gas impinging on the exposed surface. The model was verified by comparing the obtained thermal field to direct measurements by thermocouples placed along the rod and to the thermal field obtained with a numerical simulation. Results were found to be in good agreement with the experimental measurements and the numerical results.