The 3 commercially available CrC-based powders with different kind of matrix (Cr 3 C 2 -25%NiCr; Cr 3 C 2 - 25%CoNiCrAlY and Cr 3 C 2 -50%NiCrMoNb) were deposited by HVOF JP-5000 spraying gun, evaluated and compared. The sliding wear resistance, measured at room and elevated (T=600°C) temperature according to ASTM G-133, the influence of heat treatment on the microstructure and properties, as well as the oxidation resistance in hot steam environment (p=24 MPa; T=610°C) were evaluated with respect to their potential application in steam power industry. The surface oxidation and microstructure changes were evaluated by SEM and XRD. The NiCr matrix proved to provide high oxidation and sliding wear resistance of the coating regardless volume content. On the contrary, the Cr 3 C 2 -25%CoNiCrAlY coating was subjected to massive oxidation of carbide particles. The low cohesive strength and high porosity of Cr 3 C 2 -25%CoNiCrAlY was identified responsible for its poor oxidation resistance in hot steam environment. The sliding wear resistance was found comparable at room temperature, regardless the matrix composition and content, while at elevated temperatures, the higher volume content of matrix led to higher wear of coating material.

Lowering the thermal energy and increasing the kinetic energy of sprayed particles by newly developed HVAF systems can significantly reduce material decarburization, and increases sliding wear and corrosion resistance of hard metal coatings, making HVAF coatings attractive both economically and environmentally over its HVOFs predecessors. Two agglomerated and sintered feedstock powder chemistries, respectively WC-Co (88/12) and WC-CoCr (86/10/4), with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Respective dry sliding wear behaviours and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al 2 O 3 counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviours were evaluated via standard Neutral Salt Spray (NSS), Acetic Acid Salt Spray (AASS), accelerated corrosion test and electrochemical polarization test at room temperature. Optimization of coating tribological properties are discussed regarding the suitable selection of primary carbide size for different working load applications.