Deposition strategy driven tailoring of tribological performance in thick-wall robotic wire arc additive manufacturing of Al–Si alloys

Abstract

This study investigates the influence of deposition strategy on the microstructural evolution and tribological response of AA4043 thick walls fabricated via robotic WAAM using CMT–GMAW. Unidirectional (U) and bidirectional (B) triangular weaving strategies were comparatively examined to establish a quantitative process–structure–tribology relationship. Multi-scale characterization (FESEM, EDS, XRD texture analysis, and TEM) correlated grain morphology, texture intensity, silicon segregation, and porosity with hardness and reciprocating wear behavior. Unidirectional deposition produced refined, less elongated grains with reduced Si segregation and lower porosity, resulting in improved hardness and lower wear loss ( $0.0095\mathrm{g}$ at $20\mathrm{N}$ ). In contrast, bidirectional deposition generated elongated grains, stronger $\{111\}$ texture, enhanced Si enrichment ( $\sim$ 8.3 wt.%), and higher porosity, leading to increased wear ( $0.0119\mathrm{g}$ at $20\mathrm{N}$ ). Wear debris analysis revealed a load-driven transition to crack-assisted delamination, with EDS confirming adhesive Al transfer at elevated load. Overall, deposition strategy governs wear resistance through coupled effects of grain refinement, texture evolution, porosity, and load-dependent adhesive deformation mechanisms, establishing unidirectional deposition as tribologically superior for WAAM Al–Si components.