Influence of temperature-dependent absorptivity on solid surface heated by CO2 and Nd:YAG lasers

The most widely used high power industrial lasers are the Nd:YAG and CO2 lasers, especially in the cutting process and also in the field of surface engineering, due to their precision of operation, short processing time, localized treatment, low thermal distortion, and their precise control of depth treatment. One of the most important parameters affecting the laser–surface interaction is the material's ability to absorb laser energy. This absorptivity is an unknown parameter for which experimental data at high temperatures are currently unavailable. A finite difference method is used to solve numerically the derived nonlinear heat equation taking into account the temperature-dependence absorptivity, input intensity laser pulse heating of a semi-infinite solid material including a convective boundary condition at the surface. Absorptivity was modeled as a temperature-dependent variable function, for the theoretical Hagen-Rubens, and Bramson relationships. Their influence on temporal and spatial evolution of the temperature profile in the material during laser heating is investigated and discussed. In case of constant absorptivity, underestimated temperature is found mainly at the surface of the material.