Characterisation of HVOF sprayed NiCrAlY–0˙4 wt-%CeO2 coatings on superalloys

Abstract

In the present work, metallurgical and mechanical properties of high velocity oxy fuel thermal sprayed NiCrAlY–0˙4 wt-%CeO2 coatings on Ni and Fe based superalloys have been investigated. The microstructural morphologies, composition, and phases of the coatings were characterised using the techniques such as optical microscopy, field emission scanning electron microscopy /energy dispersive spectroscopy and X-ray diffraction. The mechanical properties of coatings such as microhardness and adhesion strength were measured. The coatings exhibited characteristic splat like, layered morphologies due to the deposition and resolidification of successive molten or semimolten powder particles. The coatings contained less than 1˙4% porosity and showed the measured hardness values in the range of 649–753 HV. Average bond strength of the coating was found to be 45 MPa. The observed higher values of microhardness of the coated samples might be attributed to the addition of small amount of rare earth oxide CeO2 in the coatings.