Characterization of atmospheric plasma spray NiCr–Cr2O3–Ag–CaF2/BaF2 coatings

A blended NiCr–Cr2O3–Ag–CaF2/BaF2 feedstock was sprayed using an atmospheric plasma spray process. Physical and thermophysical properties of each constituent phase are quite different and resulting interactions of each constituent with the plasma jet can be expected to be different. Thus, attempts to change the plasma jet characteristics by changing the hydrogen gas flow rate in view of the thermophysical properties of the plasma jet were tried. Phase compositions and microstructures were evaluated as a function at hydrogen gas flow rate. The effects of phase composition and microstructure on the Vickers microhardness and bond strength were also evaluated. For empirically tracing each constituent particle trajectory, spot spraying bead was produced. Finally, particle temperature and velocity as a function of the hydrogen gas flow rate was measured using alumina–titania particle instead of the blended feedstock.