Influence of Laser Shock Peening without Coating on Surface, Mechanical, Corrosion, and Tribological Characteristics of AA7075/h-BN Nanocomposites

AA7075 metal matrix composites have been widely used for their high strength-to-weight ratio. However, their relatively poor surface and tribological characteristics restrict their wider application in aerospace and automotive components. This study investigates the effect of laser shock peening without coating (LSPwC) on surface, mechanical, corrosion, and tribological properties of stir-squeeze cast AA7075, AA7075/0.5h-BN, and AA7075/1.0h-BN nanocomposites. LSPwC was carried out using a 1064 nm wavelength, 400 mJ laser pulse energy, 7.95 GW/cm2 power density, and 75% overlap. The LSPwC-treated specimens exhibited a significant improvement in surface hardness of ∼7% for as-cast AA7075 and ∼13% for AA7075/h-BN MMCs, primarily due to grain refinement, induced compressive residual stress (CRS), and intermetallic compound (IMC) strengthening. A reduction in surface roughness (Ra) of ∼12% was observed in LSPwC-treated AA7075/h-BN in contrast to that in AA7075. Corrosion characteristics were enhanced through the formation of a stable and uniform passive oxide layer, thereby minimizing pitting corrosion in sacrificial anodic environments. The synergistic effect of h-BN and LSPwC enhanced surface wettability and tribological characteristics, resulting in a transfer of severe abrasive, adhesive, and delamination wear into predominantly milder adhesion and delamination wear. Overall, LSPwC-treated AA7075/1.0h-BN composites obtained the lowest SWR (0.1813 mm3/KN-m at RT and 0.8233 mm3/KN-m at 150 °C) and CoF (0.294 at RT and 0.314 at 150 °C).