Thermal simulation of laser surface modification of H13 die steel

In this study, the effects of laser parameters on the properties of glazed die steel were investigated. A Rofin DC-015 diffusion-cooled CO2 slab laser with 10.6 µm wavelength was used. Die steel sample surfaces were prepared with a 3 µm roughness and chemically treated to improve CO2 laser wavelength absorbance. One set of processing parameters were processed through the thermal simulation program and correlated with physical results determined from actual test samples. Set processing parameters were 1138 W peak power, 2900 Hz PRF, 24% duty cycle and 261 mm/s traverse speed. Scanning Electron Microscopy (SEM) micrographs and micro-hardness properties of the affected surface were measured. An analytical mathematical model of the heat field generated in the laser glazing process was used to predict the nominal temperature distribution in the surface and dimensions of melt pool. A thermal model using point source surface energy inputs was used to predict the thermal profiles in the die steel. This allowed estimation of the depths of microstructurally altered regions. For higher energy absorbance, the depth of the glazed surface increased from 20 μm to 40 μm. At high nominal heating to cooling rate ratios, high micro-hardness values were recorded.