Transitioning surface wettability of Ti6Al4V via laser ablation and post-processing methods

Abstract

The surface wettability of metals and alloys holds significant interest for industrial, commercial, and research applications. Laser-based texturing has emerged as a prominent technique for modifying wettability due to its precision, versatility, and automation compatibility. This study explores the wettability modification of Ti6Al4V alloy through laser ablation, followed by heat treatment and chemical coating. Initially, laser scanning speed and power are varied to create textured surfaces, which are then analyzed for feature dimensions using profilometry. Optimal parameters, determined as 9 mm/s scanning speed and 60 W power, yielded low-aspect-ratio features to enhance surface roughness and promote wettability. Using these parameters, three sets of laser-ablated samples were prepared in grid patterns with varying line spacing. Two of these sets then underwent post-processing: low-temperature heat treatment and hexadecyltrimethoxysilane (HTMS) coating. Contact angle (Ɵ) results revealed that Ɵ decreased from 72.4 ± 3.1° on the untreated surface to 34.5 ± 2.3° for the laser-ablated sample, indicating enhanced hydrophilicity achieved through laser texturing. Post-processing treatments further altered the wettability: heat-treated samples exhibited a Ɵ of 91.8 ± 2.3°, while chemically coated samples showed a Ɵ of 124.8 ± 2.1°. These results demonstrate a transition in wettability toward a hydrophobic state, with HTMS coating being the more effective treatment for achieving this shift. Further, morphology analysis revealed randomly oriented thread-like micro/nanostructures, with coarsening of features in heat-treated samples. This study confirms that laser ablation effectively creates microscale surface features to enhance wettability, while post-processing enables a controlled transition from hydrophilic to hydrophobic states. This tuneable wettability offers promising applications for multi-functional surfaces and heat transfer systems.