Structural features of steel pulsed laser treatment within a permanent magnetic field

Abstract

It is shown that laser melting of a steel surface within a permanent magnetic field enhances the Marangoni effect, i.e., it intensifies metal mixing up to removing part of a thin liquid metal layer from an irradiated surface. It is established that during laser thermomagnetic treatment under the action of Lorentz forces the depth of hardened layer increases by 15–25%. It is established by calculation that during laser processing within a permanent magnetic field under action of the Righi-Leduc effect, temperature gradients, the level of thermal stresses and degree of metal local plastic deformation within the irradiated zones decrease. This leads to a reduction in steel surface layer hardness by 15–20% compared with laser hardening without applying a magnetic field. It is shown that during laser thermomagnetic treatment, under magnetostrictive effects action, partial decomposition of laser-hardened martensite proceeds with dispersed carbide hardening action. As a result of occurrence of independent low-temperature tempering within steel there is a reduction in structural stresses and the danger of crack formation.