Nayebi M. Laser Forming by Nanosecond Pulses

The increase of productivity and quality of laser processing of intractable materials is discussed in this thesis. It was established numerically and experimentally that at laser milling of intractable materials by means of Q-switched lasers the maximum thickness of removed material could be achieved, even with materials that do not form liquid phase at laser heating. The worst productivity and quality of laser processing was observed for hard-to-melt materials that undergone phase transformations from solid state to vapor with further uncontrolled deposition of erosion products on workpiece surface. Moreover, the chemical composition of surface layers changes depending on laser processing regimes. It was shown that maximum productivity of laser milling of intractable materials could be achieved at laser pulse frequencies lower than 10 kHz that enable longest pulse duration. In order to obtain the lowest surface roughness it is necessary to process each surface element twice with subsequent changing of focal position at each laser pass.