Liquid-Phase Assisted Laser Preparation of Cemented Carbide Surface Textures and Study on Their Tribological Properties

Surface texture, as an effective approach to improve lubrication and tribological characteristics at the sliding interface, was introduced into the tool manufacturing process. In order to improve the thermal effect and melt recast phenomenon of laser processing method on cement carbide surface, liquid-phase assisted laser processing method was introduced in this study. Two groups of textured type were prepared on YT15 cemented carbide surface using laser cross scanning method under air medium and auxiliary liquid phase (the volume ratio of ethanol to hydrogen peroxide is 50:1) respectively. The surface morphology and element content of test samples were measured with Quanta 200 scanning electron microscope, energy spectrum, and X-ray diffraction, and then the wettability were obtained with SDC-100 contact angle measuring instrument. The subsequent tribological test was carried out using MWF-500 reciprocating friction and wear testing machine under dry sliding, oil, and oil-MoS₂ lubrication condition. The results showed that the textured surface of laser processing in air medium was obviously blackened, and the oxygen content increased from 13.35% to 27.9%. TiO and CoO were found on the processed surface. For the laser processing surface with liquid-phase assist, the micro-pits of texture morphology were more uniform than that of air medium case. The oxygen content decreased from 13.35% to 8.63%, and no obvious oxidation and melt recasting phenomenon were found. The wettability of cemented carbide surface was improved due to better surface texture processing quality. Under three lubrication conditions, the friction coefficient of textured sample prepared under liquid-phase assisted environment was the smallest. The friction coefficient in oil lubrication, was reduced by 34% and 28%, compared to the original surface and laser processing surface in air, respectively. It indicated that the laser processing surface with liquid-phase assist has obvious advantages in regulation the interfacial friction and wear. The main reason was that the auxiliary liquid played a key role in cooling and protecting action of the machined surface. The bubbles, generating at the solid-liquid interface due to the laser heat effect, scattered the laser beam and carried out the processed melt meanwhile. Thus, the lubricating medium was easier to penetrate and spread between the contact interfaces, and the tribological characteristics was improved. The main contribution of this work was in providing a new processing method to prepare surface texture of better surface micro-pits quality and interfacial regulation of friction and wear.