Tailoring microstructure for enhanced mechanical and wear performance of wire arc additively manufactured SS 316 L: Role of interlayer cooling time

Wire arc additive manufacturing (WAAM) is known for its economic production of large, low-complexity metal components. However, one major issue with WAAM is significant heat accumulation during continuous layer deposition. Component's internal energy is gradually raised because of high heat input. This issue directly impacts fabricated components' geometrical accuracy, microstructure, mechanical properties, and wear performance. Interlayer cooling time plays a vital role in efficiently mitigating high heat accumulation during deposition without adding any additional setup with WAAM system. Present study systematically investigates the influence of interlayer cooling time ranging from 1 to 4 min on WAAM-printed SS 316 L walls to address this issue. Microstructural analysis displayed gamma-austenitic phase dominance with delta-ferrite in various morphologies. At higher cooling times refined equiaxed grains with skeletal and lathy ferrite were observed, while samples with lower cooling time of 1 min displayed coarse grains with residual ferrite. Mechanical tests demonstrated a 16.6 % enhancement in microhardness and a 14.5 % improvement in UTS with the increase of cooling time from 1 to 4 min, while elongation decreased by 10.6 %. Wear performance was also enhanced at higher cooling times with a decrease in coefficient of friction, wear rates, groove depths, and surface roughness. Additionally, wear mechanism analysis underlined that abrasive wear dominated at lower loads (5 N), while abrasion, adhesion, and oxidative wear dominated at higher loads (7.5 N and 10 N). Samples with higher cooling times exhibited better wear resistance and minimal material loss, thus emphasizing the importance of optimized cooling times in improving quality of WAAM-fabricated components.