Light metal alloys are nowadays widely used as structure materials in aerospace, transportation and electronic industries due to their good strength and light weight. One of the issues is their poor surface hardness resulting in poor wear resistance and shorter life time. Many efforts have been made to hardface the light metal alloys by using laser cladding, alloying, plasma spraying and other surface treatments. However, almost all of these processes are thermal process which means a local melt pool or high temperature is formed during the process, which will induce some challenges like the lighter element burning, porosity and cracking. Nano powders have many unique properties to be a good candidate for hardfacing the light metal alloys. During a thermal process, however, the nano powders will easily be completely melted into the melt pool and then solidified a microstructure without nano characteristics.
We have recently developed a novel process: nano powder cold enhancing of light metal surface by laser shock peening process. This is a cold process, by which the nano powders are squeezed into the surface of the light metal alloys by the very high pressure (up to Giga or even tens of Giga Pascal) induced by the laser shock peening process.
This paper reports the research work on the nano WC powder cold enhancing of aluminum alloy surface by using a 50J Q switch Nd:YAG laser system for shock peening, focusing on the process parameters, the nano powder, the X-ray confirmation of the squeezed nano particles in the surface layer, the microstructure, the element distribution, the hardness, the wear resistance and the residual stress. The research approves that the surface hardness and wear resistance of the aluminum alloy are obviously improved by the nano powder cold enhancing by laser shock peening process.