Abstract:
Microstructure and mechanical properties of cold-spray coatings are usually required in order
to explore the potential industrial application of the latter. This article demonstrates the successful formulation of Ni-20Cr and Ni-50Cr coatings on two boiler steels, namely, SAE 213-T22
and SA 516 steel by cold-spray process. The microstructure, coating thickness, phase formation,
and microhardness properties of the coatings were evaluated. The coatings were subjected to
cyclic heating and cooling cycles at an elevated temperature of 1173.15 K (900 C) to ascertain
their high-temperature oxidation behavior. Moreover, these cyclic exposures can give useful
information regarding the adhesion of the coatings with the substrate steels. Of all the coatings,
the Ni-50Cr coating on SA 516 steel had a maximum average hardness value of 469 Hv. As
observed from the surface field emission–scanning electron microscopy (FE-SEM) analysis, the
coatings were found to have nearly dense microstructure with the sprayed particles in interlocked positions. It was concluded that the cold-spray process is suitable for spraying the
preceding powders onto the given boiler steels to produce nearly dense and low oxide coatings.
The coatings, in general, were found to follow the parabolic rate of oxidation and were successful in maintaining their surface contact with their respective substrate steels.
