The effects of morphology, microstructure and surface chemistry on the wettability characteristics of high power diode laser treated metals

Abstract

This work elucidates and analyses the factors responsible for modifications of the wettability characteristics of metallic materials after high power diode laser (HPDL) treatment. It was found that interaction of EN3 and EN8 mild steel with HPDL radiation resulted in the wettability characteristics of the mild steels altering to various degrees depending upon the laser processing parameters. Such changes in the wettability characteristics of the mild steels were found to be due essentially to: (i) modifications to the surface roughness; (ii) changes in the surface O2 content and (iii) the increase in the polar component of the surface energy. Work was conducted to isolate each of these influential factors, thereby allowing the magnitude of their influence to be determined. This analysis revealed that surface roughness was the primary influential factor governing changes in contact angle, θ, and hence the wettability characteristics of the mild steels. Surface energy, by way of microstructural changes, was also shown to influence, to a lesser extent, changes in the wettability characteristics, whilst surface O2 content, by way of process gas, was found to play a minor role in inducing changes in the wettability characteristics of the mild steels.This work elucidates and analyses the factors responsible for modifications of the wettability characteristics of metallic materials after high power diode laser (HPDL) treatment. It was found that interaction of EN3 and EN8 mild steel with HPDL radiation resulted in the wettability characteristics of the mild steels altering to various degrees depending upon the laser processing parameters. Such changes in the wettability characteristics of the mild steels were found to be due essentially to: (i) modifications to the surface roughness; (ii) changes in the surface O2 content and (iii) the increase in the polar component of the surface energy. Work was conducted to isolate each of these influential factors, thereby allowing the magnitude of their influence to be determined. This analysis revealed that surface roughness was the primary influential factor governing changes in contact angle, θ, and hence the wettability characteristics of the mild steels. Surface energy, by way of microstructural changes, was...