Abstract
In laser surface modification with a molten state, cracks are generated on the laser irradiated surfaces under unsuitable conditions. This phenomenon is one of the main problems regarding industrial use. In this study, it is considered that the generation of cracks will be caused by a tensile stress based on the phase change of material. Thus, an analysis of thermal stress including the phase changed process is suggested. The thermal stress distribution is calculated using FEM with consideration of the complicated boundary conditions due to the phase change. And, the laser beam was practically irradiated on the surface of cemented carbide. The forms of generated cracks were examined, and the following results were obtained. Tensile stress above 1200 MPa arises in the solidified region of material, whose value exceeds the tensile strength of material used. The behaviour of generated cracks could be obviously explained with consideration of both the change with time and spatial distribution of the thermal stress.
