The use of thermally sprayed coating deposited by high velocity oxy-fuel (HVOF) is a very effective way to protect various mechanical components. More specifically, thermally sprayed carbides such as Tungsten carbides and Chromium carbides are widely used by the industry due to their very good tribological properties. Carbide-based are cermet and are composed of two distinct phases, the hard carbide phase (composed of tungsten carbides or chromium carbide particles) and the ductile metallic binder phase. Despite having excellent properties some awareness is raised concerning the ecological, health, and economic aspects of using Co-based carbides. Indeed, the Co used is harmful to the environment, toxic for the people that work on it, and the reserves available are very concentred in small geographical areas. Moreover, limitations exist regarding the HVOF process that can induce some decarburization, which leads to tribological properties loss. Consequently, a newer spray process, the high-velocity air fuel (HVAF) can be used, and greener binders need to be found for tungsten carbide-based coatings. Similar issues are also observed for chromium carbide-based coatings to a lesser extent.

This thesis aims to study new types of greener binders, and manufacturing routes for tungsten carbides and chromium carbides-based coatings deposited by high-velocity air fuel. To do so, a bibliographical review of tribological properties, wear, and corrosion has been done. As well as testing all these properties for different coating with greener types of binders or new manufacturing routes. The microstructural investigation was carried out using a scanning electron microscope. The wear behavior has been investigated through ball-on-disk testing, the erosion properties by air jet testing, and finally, corrosion testing with an electrochemical cell.

The results have shown for tungsten carbides that the new iron-based binders have similar wear properties and coefficient of friction compared to the reference CoCr-based binder. Moreover, it was found that thinner feedstock particles for Fe-based binders exhibit better anti-wear properties compared to the coarser WC-Fe-based ones. The coefficient of friction was similar for tungsten carbide coatings. Regarding erosion performance, the iron-based binder exhibits lower erosion properties but is still very close to the reference coating. Finally, the thin particle size cut of iron-based binders has shown better anti-corrosion properties than the reference cobalt-chromium-based matrix coating. Consequently, it is possible to say that thin iron-based tungsten carbides are a promising alternative to standard WC-CoCr coatings.