Microstructural Characterization of Plasma Sprayed Ni-5wt.%Al Coatings Using Rietveld Refinement

This work is focused on the microstructure study of nickel aluminide (Ni-5wt.%Al) deposited on an A37 steel substrate using Rietveld refinement of x-ray diffraction data. These coatings are elaborated by atmospheric plasma spray, which consists of introducing the initial feedstock material, in the form of powder, into a flame of 20,000°C temperature, melting it and spraying it on a surface to coat. The deposit was realized on two types of substrates: the first was on a non-heated substrate, and the second coating was deposited on a heated substrate at 150°C. X-ray diffraction analyses are conducted on the coating to investigate its microstructure and phases, with the Rietveld refinement technique employed to quantify the various phases present. The results showed that the nickel aluminide coatings present the formation of new phases such as Ni₃Al and NiO. The surface roughness and micro-hardness values of the coatings have also been evaluated, and the mean hardness of the coating was found to be about 476 H_V and 493 Hv for coatings deposited on non-heated and heated substrates, respectively.