Performance of Sustainable WC-FeCrNiMo Coating by High-Velocity Air Fuel Spraying: A Potential Alternative to WC-Co Based Coatings

Abstract The quest to find an alternative to Co-based metal binders has been of prime importance within the thermal spray community to develop sustainable, Co-free WC-based cermet coatings. In this study, we investigated WC-based coatings with FeCrNiMo as a Co-free binder, as an alternative to traditional WC-CoCr coatings. WC-FeCrNiMo powders with particle sizes of fine (25/5 µm) and coarse (45/15 µm) were deposited via high velocity air fuel (HVAF) spraying with various nozzle configurations. For benchmarking, a standard WC-CoCr coating with two particle sizes (45/15 and 30/5 µm) was included in all analyses and testing. The microstructure and mechanical properties of the coatings were thoroughly examined. Performance was evaluated through ball-on-disk sliding wear tests and air jet erosion tests. Microstructural analysis showed dense coatings, and XRD results confirmed that all coatings maintained the main phase composition of the feedstock, demonstrating HVAF's efficiency in preserving feedstock integrity. In sliding wear tests, the fine WC-FeCrNiMo coating showed a 57% lower wear rate (8.42 × 10 −8 mm 3 /Nm) compared to the coarser WC-FeCrNiMo coating (13.23 × 10 −8 mm 3 /Nm). In comparison, the standard WC-CoCr system exhibits an overall lower wear rate (2-3 × 10 −8 mm 3 /Nm), attributed to its better strain hardening. Although WC-FeCrNiMo coatings had higher wear rates, their values remained within the same order of magnitude (~10 −8 mm 3 /Nm), which is extremely low and suitable for many demanding tribological applications. Under erosion conditions, no significant difference in removal mechanisms was observed; however, the standard WC-CoCr coatings had better erosion resistance than WC-FeCrNiMo coatings. The overall findings from this study convey that WC-FeCrNiMo coatings are promising, offering performance comparable to Co-based binders.