Tribological Performance of WC-Reinforced Wire-Arc Directed Energy Deposited SS316L Composite Surfaces at Room and Elevated Temperatures

:Wire-arc directed energy deposition (WA-DED) was used to deposit SS316L composite coatings with 0, 10, and 20 wt.% WC on EN8 forged steel substrates. Dry sliding tests were conducted at room temperature (RT) and 500 °C under 10 N and 40 N to examine how WC content governs wear regime transitions across abrasive, adhesive, oxidational and thermomechanical regimes. At 10 wt.% WC, the coating shifts RT behaviour into an Archard-compliant abrasive-adhesive regime, recording the lowest wear coefficients (54.64 × 10−6 mm³/N-m at RT–10 N; 110.47 × 10−6 mm³/N-m at RT–40 N), 65% and 58% below the unreinforced substrate, while retaining oxidative protection at 500 °C. At 20 wt.%, WC loading crosses a microstructural percolation threshold where third-body brittle fracture dominates at RT–10 N (relative wear 1.80), and thermomechanical interfacial fatigue combined with WC→WO3 decomposition drives severe degradation at HT–40 N (relative wear 1.78). XRD confirmed partial WC→W2C decarburization in both reinforced coatings, with additional WO3 formation in the 20 wt.% sample. At 500 °C, all surfaces enter Quinn's oxidational regime; a protective glaze reduces wear at 10 N by 43.6% relative to RT. A wear regime transition map on normalised pressure–homologous temperature axes positions the 20 wt.% coating within the severe oxidational–thermomechanical fatigue zone, establishing predictive safe-operating criteria. The 10 wt.% WC coating achieves performance comparable to laser-DED coatings at lower process cost and higher deposition rate, making it the optimal composition for combined RT and elevated-temperature wear resistance.