Ultrasonic Vibration-Assisted Laser Surface Engineering of Structural Alloys
Abstract
Simultaneous application of ultrasonic vibrations in conventional solidification processing techniques has been reported to be highly successful in elimination of dendritic microstructure in alloys and improved particle distribution in composites. However, similar studies in rapid solidification processing techniques such as laser processing have not been extensively performed. Hence, in this study, the major objective was to develop ultrasonic vibration-assisted laser surface engineering that involves simultaneous application of vertical ultrasonic vibrations on the substrate. This was achieved by attaching the substrates on a probe generating ultrasonic vibrations and simultaneously performing laser processing on the substrate. It should be noted that although laser surface engineering has recently emerged as one of the most popular non-conventional surface modification techniques as it offers refined microstructure, elemental redistribution, and excellent process control, it is often also associated with undesirable features such as dendritic, textured microstructure and elemental segregation. Detailed analysis on the effect of ultrasonic vibrations on the microstructural evolution, crystallographic texture, and phase evolution on laser surface melted and composite cladded commercial aluminum and titanium alloys is presented. Also, the effect of the microstructural, texture and phase changes in surface mechanical, tribological, and electrochemical properties was systematically studied. Furthermore, the effect of ultrasonic vibrations on laser surface engineering techniques without extensive melting such as laser surface texturing on stainless steel substrates was performed. The studies were primarily focused in investigating the influence of the ultrasonic vibrations on the surface texture evolution and its role in improving the tribological performance during steel-on-steel wear upon the external addition of graphene as a lubricant. The studies conclusively showed that ultrasonic vibrations are highly efficient in generating a significantly refined and equiaxed microstructure with superior surface mechanical and tribological properties.
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- OSU Dissertations [11222]