A Comparative Study on the Laser Surface Melting and Laser Surface Cladding of H13 Tool Steel

The present work investigates the effect of laser processing parameters on the evolution of microstructure, phases, and properties, following advanced materials manufacturing techniques such as laser surface melting (LM) and laser surface cladding (LC) of H13 tool steel. The laser parameters such as laser power, scan rate, and powder feed rate are optimized to achieve the desired combination of microstructure and properties of H13 tool steel substrates in annealed and tempered conditions, through these techniques. In LM specimens, the melt zone displays a hypoeutectic microstructure consisting of fine martensite laths (confined only to prior austenitic regions), retained austenite, and mixed carbides. Similarly, the clad zones in LC specimens exhibit austenitic dendrites manifested partly as fine martensitic laths and the rest as retained austenite with inter-dendritic spaces containing mixed carbides. Notably, residual compressive stresses prevail in the specimens subjected to LM and LC, the magnitude of which is directly related to the laser energy/power density. The mechanical properties at the different zones of the surface-engineered structures are systematically evaluated to establish the microstructure-property correlation in H13 tool steel upon LM and LC. Interestingly, both these surface engineering processes are noted to substantially enhance the hardness and wear resistance of the H13 tool steel substrate. A profile of microhardness with depth from the surface reveals an increasing trend up to the heat-affected zone following which it reduces, the substrate showing the least value. The role of laser process parameters, evolved microstructure and phases, as well as the efficacy of the annealed and tempered H13 tool steel substrates in modifying the hardness as well as wear resistance of the tool steel is thoroughly assessed.