Sustainable WC-Fe based coatings by High-Velocity Air Fuel spraying: A potential alternative to WC-Co based coatings

The quest to find an alternative for WC-Co-based coating has been of prime importance within the thermal spray community to develop sustainable wear-corrosion-resistant coatings. This is mainly driven due to the growing concerns about the potential health hazards and scarcity of cobalt reserves, prompting researchers to explore Co-lean or Co-free metal binders as an alternative to WC-Co-based coatings without compromising coating performance. High-velocity air fuel (HVAF) spraying has become a popular choice for depositing WC-based coatings due to its low combustion temperature and high kinetic energy, which effectively minimizes decarburization during deposition. The objective of this work was to explore Fe-based green binder as a potential alternative to Co-based binder. WC-Fe-based powders with varying particle sizes (fine 25/5 µm and coarse 45/15 µm) were deposited using HVAF spraying with different nozzle configurations along with standard WC-CoCr powder as reference. The microstructure, hardness and fracture toughness of the deposited coating were thoroughly analyzed. Performance evaluation including pin-on-disc wear test, air jet erosion test and corrosion tests was carried out. The results show that coatings with Fe-based binders look very promising and can provide similar performance as the Co-based binders in different operating environments.