The effect of spray parameters on the properties of high velocity oxy-fuel NiAl intermetallic coatings

A high velocity, oxy-fuel (HVOF) thermal spray process has been used to deposit two commercially available NiAl intermetallic powders, one reaction sintered and the other inert gas atomised. It was possible to deposit high quality coatings of NiAl intermetallic at rates comparable to those of non-metallic coatings. The coatings were characterised in terms of microstructure, oxygen content, porosity and permeability, Youngʹs modulus and hardness. Coating characteristics and properties were found to be dependent on both the powderʹs particle size and the spray parameterʹs oxygen to fuel ratio. The preferred spray parameter was that of a high oxygen to fuel ratio equivalent to 80% stoichiometry, a spherical inert gas atomised powder with a narrow particle size range between 15–45 μm and a small percentage of particles >50 μm.