Influence of laser and laser-ultrasonic treatments on the durability varying of steel friction surfaces

The damage of the sliding friction surfaces of constructional steel 40Kh over the stainless steel 12Kh18N10T is researched. From the comparison of the damage processes for steel 40Kh in its initial annealed state, after the laser and laser-ultrasonic hardening to the different values of surface micro-hardness and separately after the volume heat treatment it’s established that in the whole interval of micro-hardness values not related to the dispersion degree of structures the damage is of fatigue nature. The trend of durability increasing and damage rate decreasing is discovered under the escalation of friction surface micro-hardness. The empirical analytic relations are obtained from the analysis of experimental data. These relations tie the damage parameters with the micro-hardness characteristics of surface. It is shown that the damage process comes with forming the special structural-stressed state in Saint–Venant area, which is characterized with the constant level of hardness not related to the previous material status.