Synthesis of laser beam rapidly solidified novel surfaces on D2 tool steel

Surface layer of D2 tool steel was subjected to laser surface melting using continuous wave 2.5kW CO₂ laser in point source melting mode. The processing parameters were varied to achieve a uniform depth of around 2 mm. Microstructural study revealed epitaxial growth of fine dendritic structure with secondary dendrite arm spacing in the range of 20-25 μm. The phases in the parent annealed sample were BCC ferrite and chromium rich M₇C ₃ carbide. The major phase after laser treatment was austenite and M₇C₃. The average hardness of annealed sample was 195 HV which increased to 410 HV after laser melting. Corrosion studies in 2% HCl solution exhibited a drastic improvement in corrosion resistance in laser treated samples. Improvement in properties is attributed to the refinement and uniformity of microstructure in the rapidly solidified surface. The case of a moving heat source was subjected to computer aided simulation to predict the melt depth at different processing conditions in point source melting mode. The calculated depths using the model, in ABAQUS software was found in good agreement with the experimental data.