A Study of the Breakdown Mechanism of AISI 304 Stainless Steel, Type 2024 Aluminum and Various Titanium Coatings.

摘要

An investigation, experimental and theoretical, into the breakdown mechanisms and associated minimum power levels required for the breakdown and unipolar arcing was conducted for AISI 304 stainless steel and Type 2024 aluminum. The experiment was conducted using a neodymium-glass Q-switched laser. A system of filters was used to attenuate the irradiance on target to the point at which no damage was discernible following laser-target interaction. Experimental results show that above a certain critical power density, surface breakdown occurs. The primary mechanism of surface damage at the power density threshold is by unipolar arcing. Titanium coated stainless steels were exposed to energy density levels on the order to 5 GW/sq cm. The titanium coatings significantly reduced or eliminated the number of unipolar arcs observed. A model is proposed for the physical processes involved in the first few nanoseconds before breakdown.