Effects of laser processing parameters on texturized layer development and surface features of Ti6Al4V alloy samples

Abstract

Surface engineering is widely used in different areas, such as the aerospace industry or the biomechanical and medical fields. Specifically, laser surface modification techniques may obtain specific surface finishes for special applications. In texturing laser procedures, the control of processing parameters has a great influence on the geometry and characteristics of the treated area. When these processes are carried out on titanium alloys, thin oxide layers are usually developed on the irradiated surface, formed through the thermochemical combination of vaporized material with atmospheric oxygen in the air. In thermal oxidation treatments of Ti6Al4V, the highest concentration of oxides is mainly composed by rutile (TiO2), producing surface property modifications such as hardness, among others. In this research, a thermochemical oxidation of Ti6Al4V alloy has been performed through laser texturing, using laser scanning speed (Vs) and pulse rate (f ) as process control variables, and its influence on the beam absorption capacity of the modified layer have been analyzed. Combined evaluations of microgeometrical features and mechanical properties, such as hardness, verified that, by means of laser texturing treatments, the ability to generate specific topographies and increase the initial hardness of the alloy is obtained. The most advantageous results for the increase of hardness by thermochemical oxidation have been detected in low scan speeds of laser beam treatments, resulting in an increase of approximately 270% using a scanning speed of 10 mm/s. On the other hand, a dependence between roughness values, in terms of Ra and Rz, and the energy density of pulse (Ed) has been observed, showing higher values of roughness for a 17.68 J/cm2 energy density of pulse.