Research study of the elastic-strength and tribological characteristics of the surface after laser processing of the slurry coatings

The research paper examines the results of applying the proposed method of the laser processing of the composite slurry coating on the steel samples` surface such as 12Kh2N4A-Sh. An increase in the elastic-strength and tribological characteristics` surface occurs as a result of the imposition of several physicochemical processes in the laser-impact zone on the applied composite slurry coating with an epoxy element as the base material with the laser thermal hardening, the diffusion influence on the atomic boron along grain boundaries, carbonization and the formation of a modified surface layer. The conducted research shows the gradient structure of the surface layers. The coating composition varies in the studied samples, however, for all experimental samples, the elastic-strength and tribological characteristics are higher than the corresponding characteristics of the standard steel sample as 12Kh2N4A-Sh, which has undergone the cementation process. The calculated values of the resistance indicators of the elastic and plastic deformation are confirmed by the conducted tribological tests. It is given the higher efficiency of the laser processing method of the slurry coating and it is concluded the prospects of the proposed method.

Raman random lasing in Ba(NO3)2 powder

Random lasing in Raman active material – barium nitrate powder – has been registered in two temporal regimes: nanosecond and picosecond. Stimulated Raman scattering (SRS) in Ba(NO3)2 for picosecond excitation has been shown to have much lower threshold and spectrum containing more components than for nanosecond excitation opposite to the case of a bulk medium. In picosecond regime SRS intensity increased with temperature decreasing and redistributed in favor of the higher order components. SRS pulse duration in picosecond regime was estimated to be in the range 16.5-22 ps. High conversion efficiency of SRS in barium nitrate powder in picosecond regime and its larger stability under laser impact than for bulk samples gives possibility to use it as an active material in Raman converters.

COMSOL SIMULATION OF LASER WELDING OF ALUMINUM

This research includes a Comsol Mutiphysics model describing the temperature distribution on aluminum during the laser conductivity welding process. The influence of laser power and speed on the welding process is discussed and compared with experiments. Numerical simulations of laser welding process have been performed to determine the temperature fields of laser impact to samples of aluminum. Numerical calculations are made for fiber laser. The plots of the temperature dependence on the surface and in the depth of aluminum samples on the velocity are analyzed for several power densities for this laser.