A Simplified Model for NiCr Coatings Properties Prediction Through Spraying Parameters Selection

A model was built for the prediction of HVOF sprayed NiCr particles states based on the spraying parameters. The employment of factorial design during the conduction of sprayings, allowed the determination of the contribution of each one of the spraying parameters, such as flame energy (combustion pressure and O₂/F ratio), spraying distance and feed rate, to particles velocities and surface temperatures. It was shown that similar particles velocities and temperatures were feasible through different combinations of parameters. Particles with velocities ranging as much as 300 m/s and temperatures ranging up to 350 ^oC were sprayed on an in situ curvature sensor, for the determination of evolving and residual stress. These diverse particle states combined with the flame impact during spraying produced coatings of similar thickness, but totally dissimilar properties. Real time spraying stress-evolving-, microhardness, Young’s modulus, density, oxidation and substrate temperature were interrelated to particles states, and thus spraying parameters. Furthermore, it was shown that more complex coating properties such as aqueous corrosion and adhesive wear can be indirectly linked to initial spraying parameters, thus allowing a rough estimation of the coatings performance based on them.