Structural and properties characterization of stellite coatings obtained by cold gas spraying

The work was aimed at obtaining cold gas spray deposits of stellite-6 minimizing the porosity content with further characterization of such coatings in terms of structure as well as wear and high temperature behaviour. The high strength and melting point of this alloy make the critical velocity increase; for that reason spraying stellite means a challenge. Then, although the deposition efficiencies are relatively low, the spraying parameters have been optimized leading to pore-free deposits where the slightly deformed particles clearly exhibit the dendritic structure of the feedstock.The structural changes investigated at the nanoscale level by transmission electron microscopy revealed a high deformation by twinning and the shear stresses produced by the wear conditions led to the occurrence of the hexagonal phase coexisting with the original cubic phase.Concerning the oxidation resistance, stellite coatings were capable to withstand up to 900 °C and the wear performance was improved by reinforcing the ultimate layers with alumina particles.

► Cold-sprayed stellite-6 particles deform and adhere by twinning mechanism.
► Coatings are dense and exhibit adhesion strength around 50 MPa.
► Adhesion is independent of surface preparation.
► Good performance in abrasive and sliding wear, with FCC–HCP phase transformation
► Coatings resist high temperature oxidation by developing a Cr2O3 oxide scale.