Mechanical and microstructural characterisations of NiCrCoAlYTa coatings on superalloys deposited by detonation gun technique

The microstructure and mechanical properties of detonation gun sprayed NiCoCrAlYTa alloy coatings on the selected superalloys were investigated. The coatings were characterised in relation to thickness, porosity, microhardness, microstructure, compositions, and phases across by using the techniques such as optical microscopy, X-ray diffraction, field emission scanning electron microscopy/energy dispersive analysis and X-ray mapping. The formation of spherical or elliptical shaped dendritic splats was observed in the as sprayed coatings on the superalloys. The splat morphology of the coatings is due to the deposition and re-solidification of successive molten or semimolten powder particles. The coatings showed a bond strength of 50 MPa and the surface roughness (arithmetic average height) of the coatings was found to be in the range of 6·25–7·48 μm. The porosity and microhardness of the coatings were less than 0·48% and 385–748 Hv respectively. The XRD analysis of the coatings showed the phases γ-Ni or γ′-Ni₃Al and β-NiAl inter metallic as the minor phase.