Melt-through characteristics in continuous beam irradiation of flying metal samples in flow speeds up to 85 m/s

Abstract

A flying metal target was subject to continuous wave laser irradiation in subsonic flow condition up to 85m/s. The temperature of the metal increases beyond its melting temperature in the airflow, which removes portions of the melt, thus reducing the time to its melt-through. In this work, we establish several threshold irradiances for Stainless Steel 304 (STS304) and Titanium, beyond which the aerodynamic melt-through times of each metal become shorter in the presence of subsonic airflow. The parametric dependence of the threshold irradiances is monitored through the thickness of the target and the wavelength of a beam. A 10.6μm CO2 laser and a 1.07μm fiber laser were used to irradiate the thin metal targets. The results show that the surface reaction of Titanium plays a role in reducing the melt-through time, unlike the case of STS304. The overall threshold irradiances of each target are determined to be approximately proportional to the target thickness and inversely proportional to the absorptance of the two different beams.