Effect of ultrasonic vibration-assisted laser treatment on surface roughness and wettability of aluminum

Abstract

Superhydrophobic surfaces is generally made by improving the surface roughness of materials. However, the increased surface roughness has a great impact on the service performance of the materials. In this paper, a new method was proposed by using ultrasonic vibration-assisted laser processing (UVLP) to fabricate aluminum superhydrophobic surface. The influence of ultrasonic vibration on contact angle was explained according to the Cassie equation. The microscopic contact phenomenon between the water droplet and the machined surface was simulated by geometric model. Scanning electron microscopy (SEM), three-dimensional non-contact surface profilometer, and contact measuring instrument were employed to characterize the microstructure, surface roughness, and surface wettability. Comparative experiments were conducted to investigate the effect of ultrasonic vibration on the surface morphology of laser machined aluminum. The surface arithmetic mean height Sa can be reduced about 0.21–1.83 μm due to the introduction of ultrasonic vibration. The contact angles of aluminum surface after normal laser processing (NLP) and UVLP treatment were up to 134.29° and 154.21°. The maximum contact angle after UVLP was 14.8% higher than after NLP. This method was proven to be an effective way to achieve a hydrophobic state with a low surface roughness, which made it suitable for a wide range of self-cleaning applications.