Laser Treatment of Plasma Spraying Alloyed Coatings

Abstract

Ni23Cr6Al0.4Y plasma sprayed coating on nimonic75 substrate was remelted using a 1kW continues CO2 laser. The topography, microstructure, phases and chemical analysisof plasma sprayed and laser melted regions were examined using various techniquesincluding scanning electron microscope (SEM), electron probe microanalysis (EPMA),energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The plasmasprayed coatings consisted heterogeneous microstructure of lamella with unmeltedparticles, voids, porosity and cracks. It was found that the depth of melting increasedwith increasing the specific energy. Homogenous and shiny melted regions wereachieved without voids, porosity and cracks after laser melting. Thin upper surfacelayers with shallow cracks were observed due to the rich layer of α-Al2O3 and YAlO3.No phases changed were found before and after laser melting of plasma sprayed layers.The phases formed are mixtures of γ’, β, YAlO3 in the matrix γ. The microstructureformed after laser melting is fine cells.Keywords: Plasma sprayed coating; Laser melting, Ni solid solution; YAlO3; α-Al2O3