Wear properties of surface-modified WAAM samples of AA7075 alloy with TiC nanoparticles-treated filler wire using cold metal transfer welding process
摘要
This study investigates the synergetic effects of TiC nanoparticle reinforcement and double-pass friction stir processing (FSP) on the microstructural and tribological properties of AA7075 fabricated via CMT-WAAM. While WAAM offers high deposition rates for intricate aluminium components, inherent challenges such as coarse dendritic structures and porosity often compromise mechanical integrity. To address this, a TiC nanoparticle-treated filler wire was employed, followed by surface modification via double-pass FSP. Microstructural characterization showed that refinement of grain size from 17.305 ± 4.269 µm in the as-deposited state to 4.311 ± 1.024 µm post-FSP was driven by continuous dynamic recrystallization (CDRX) and Zener pinning by TiC particles. Mechanical testing exhibited an 11.39% increase in microhardness for the WAAM-FSP specimen (176 ± 0.5 HV) compared to the WAAM (158 ± 2 HV), consistent with Hall–Petch strengthening. Tribological evaluations, conducted across varying loads (20–40 N) and sliding velocities (1.0–2.0 m/s) using Response Surface Methodology (RSM), identified an optimal operating condition at 30 N and 1.5 m/s. ANOVA established that the load is the primary contributing factor to the wear performance, outweighing the effects of sliding velocity. At these parameters, the predicted wear rate and mean COF were decreased from 0.287 × 10−6 g/N m and 0.519 (WAAM) to 0.277 × 10−6 g/N m and 0.303 (WAAM-FSP), with a desirability of 59.40%. FESEM and EDS analysis of the worn surfaces indicated a shift from severe abrasive wear in the WAAM to a stable oxidative wear regime in the WAAM-FSP samples.