Laser nitriding of tool steel: Thermal stress analysis

Lasers can be considered as one of the effective tools to nitride the metallic surfaces. This is because of the precision of operation and the fast processing time. In the present study, laser gas-assisted nitriding of tool steel (H13) is carried out. Temperature and stress fields are predicted using the finite element method. The metallurgical changes in the laser irradiated region are examined using scanning electron microscope (SEM) and X-ray diffraction. The fracture toughness of the surface is determined using the indentation tests. It is found that von Mises stress attains high values in the laser-heated regions. The residual stress predicted is tensile, and it is in the order of 450 MPa. SEM micrographs reveal that surface is free from cracks, and feathery-like compact structures are formed in the vicinity of the surface. The fracture toughness of the surface reduces after the laser treatment process because of the formation of brittle structure in the surface region.