Surface oxidation of low carbon steel during laser treatment, its dependence on the initial microstructure and influence on the laser energy absorption

Laser treatment of steels in air is accompanied with formation of oxide layer on the surface. This leads to significant change of the absorption coefficient for the laser radiation and thus influences the temperature field in the material and the level of properties modification. By the methods of X-ray powder diffraction the parameters of the oxide films formed during surface laser treatment of sheet low carbon steels with Nd:glass pulsed laser have been investigated. The obtained experimental results show that the initial microstructure influences the parameters of the formed oxide films. The kinetics of the oxide film growth at the initial stages (within the laser pulse duration, 7 ms) has been simulated by the created computer codes based on the finite elements method. During the performed simulations the temperature dependencies of the thermal conductivity and specific heat capacity have been considered. The influence of the growing oxide film on the laser energy absorption has been analysed.