Enhancing adhesion and tribological properties of Al7075 via shot peening and physical vapor deposition techniques

Al 7075 is a high-strength aluminum alloy widely used in aerospace and automotive applications; however, its surface hardness and wear resistance are limited. In this study, Al 7075 was shot peened using S110 and S230 shot types at Almen intensities of 8A and 10A, followed by TiN thin film deposition by physical vapor deposition (PVD). The coatings were produced under different target currents (2-3 A), N-2 flow rates (5-7 sccm), and duty cycles (15-30 %) based on a Taguchi L-4 design. Structural, mechanical, and tribological properties were evaluated using microscopy, microhardness, scratch, and pin-on-disk tests under dry sliding conditions. The combined treatment increased surface hardness from similar to 178 Vickers microhardness (HV) to similar to 832 HV (S230 shot and 10A with titanium nitride (TiN) coating) approximate to 395 %. Shot peening (SP) increased the surface roughness from approximately 4-5 & micro;m to 9-12 & micro;m, whereas subsequent TiN coating reduced the roughness to about 3-4 & micro;m. Scratch test results revealed improved coating adhesion, with critical load values reaching up to 27 N. Among the investigated conditions, the combination of S230 shot type with 10 Almen intensity and optimized PVD parameters (R3) provided the most favorable balance between hardness, adhesion strength, and tribological performance, demonstrating the effectiveness of SP-assisted TiN coating for enhancing the surface durability of Al 7075.