Laser gas assisted nitriding and characterization of tungsten surface

Abstract

Laser gas assisted nitriding of tungsten surface is carried out while incorporating the high pressure nitrogen assisting gas. Metallurgical and morphological changes in the laser treated layer are examined using the analytical tools. The nitride compounds formed in the surface vicinity are analyzed incorporating Xray diffractogram and Fourier-transform infrared spectroscopy. The wetting state and the free energy of the laser treated surface is determined using the droplet contact angle method. The friction coefficient of the resulting surface is measured via microtribometer and UV visible absorption characteristic of the surface is analyzed. It is found that the laser texturing of tungsten surface results in micro/nano size pillars without forming micro-cracks and large size cavities. The laser treatment gives rise to hydrophobic surface characteristic with improved UV visible spectrum absorption coefficient. The microhardness increased significantly because of the nitride compounds formed at the surface and friction coefficient shows wave-like behavior because of the surface texture. (C) 2018 Elsevier Ltd. All rights reserved.