Fe modeling of the apparent spot technique in circular laser hardening

Circular laser hardening is the laser surface treatment used in the case of cylindrical workpieces. The single-track treatment is a particular case of circular laser hardening used when only one revolution of the workpiece is executed since the treatment of a narrow surface is required. As a result, an annular narrow hardening track is obtained. During the laser hardening, the initial and final parts of the workpiece are overlapped and treated twice. The main drawback of this treatment is the back-tempering effect focused on the overlapping zone. This phenomenon leads to a hardness decrease in the overlapping zone. To avoid this problem, a new technique called apparent spot (AS) was introduced by the authors. The aim of the AS technique is to increase in a fictitious way the dimensions of the laser spot. In the case of circular laser hardening, this technique results into a high-speed rotation (up to 1,000 rpm) of the cylindrical workpiece instead of the traditional low speed. So, a uniform hardening zone without overlapping and back tempering is obtained. However, despite these benefits, there is still a lack of knowledge about the physics of this treatment in particular referring to the thermal cycle that affects the workpiece. In order to enhance the knowledge of this technique in this work, the AS was modeled via the FE approach. DEFORM software was used to model the circular laser hardening process. The software was firstly validated by a comparison with experimental results. Once the software reliability was tested, a regression model was estimated to predict the surface temperature within the treatments. Good agreement was found between the prediction model and the numerical results.