Formation Mechanism of Gradient Wettability of Si3N4 Ceramic Surface Induced Using a Femtosecond Laser

Abstract

The gradient wettability surface is processed on the surface of Si3N4 ceramics using a 1030 nm femtosecond laser. Both the microdimple morphology, surface contact angle, and surface chemical structure are determined using optical microscopy, optical profilometry, contact angle measuring instrument, and X‐ray photoelectron spectroscopy (XPS). The effects of average laser power, scanning passes, and microdimple distribution density on both surface morphology and contact angle are also studied. Accordingly, the wettability surfaces of different gradients are processed by changing the microdimple distribution density, and the flow state of the cutting fluid on the gradient wettability surface is observed using a high‐speed camera. The results show that both the diameter and depth of the microdimple increase with the increase in the average laser power and scanning passes. As the average laser power increases, the surface contact angle gradually reduces and then increases. Moreover, because of the increase in scanning passes, the surface contact angle gradually decreases. The microdimple morphology is an important factor affecting the wettability of the sample surface. Reason construction of the surface microdimple distribution density can obtain different gradients of wettability surface. Furthermore, with a larger gradient, the wetting rate of the cutting fluid will be faster.