Investigating the Tribological Performance and Wear Mechanisms of Stainless Steel 316L in Cold Metal Transfer-Based Wire Arc Additive Manufacturing Under Varied Loads and Thermal Inputs

In recent years, cold metal transfer (CMT)-based wire arc additive manufacturing (WAAM) has gained significant attention in the manufacturing sector, particularly for its ability to produce components with low thermal input and high deposition rates. This study investigated the tribological behavior of SS316L walls fabricated using CMT-based WAAM, employing a ball-on-plate linear reciprocating test with tungsten carbide (WC) counter body under varying thermal inputs and applied loads (15 N, 20 N, and 25 N). The tests were conducted for 10 min at a frequency of 15 Hz and a stroke length of 2 mm. Results indicate that the coefficient of friction (COF) increased slightly with applied loads, yielding an average COF of 0.22 across all loads. Wear-rate analysis revealed that both increased applied load and heat input led to a higher wear-rate, with the maximum wear-rate (3.39 × 10⁻³ mm³/m) occurring at high heat input and 25 N, while the minimum wear-rate (1.2 × 10⁻³ mm³/m) was observed at low heat input and 15 N. Vickers microhardness results demonstrated an inverse relationship between hardness and heat input, with hardness increasing by 11% as heat input decreased from high to low. FESEM analysis of wear tracks showed significant craters, abrasive grooves, delamination, surface cracks, and particle adhesion, identifying an abrasive-dominant wear mechanism with surface fatigue, partial adhesion, and oxidative wear. Wear debris analysis showed sharper angular particles and larger irregularly shaped flakes. X-ray diffraction (XRD) spectra confirmed δ-ferrite and γ-austenite phases pre- and postwear, with postwear analysis showing an α′-martensite peak, indicating phase transformation during wear.