Effect of TiO₂ and TiB₂ Compounds on the Microstructure and Infrared Emissivity of Spinel Ni-Cr Oxide Coatings Prepared by APS

In this study, high-emissivity NiCr oxide coatings, one with TiO₂ and one with TiB₂ compounds, were deposited on stainless steel substrates by spray granulation and atmospheric plasma spraying. The main phases in both coatings are NiTiO₃, spinel (NiCr₂O₄), and residual Cr₂O₃. The emissivity of the layer with TiO₂ was found to be higher in the 2.5-8 μm range than that of the layer with TiB₂, which is attributed to higher surface roughness and larger particle size. These results indicate that the NiCr oxide coatings with TiO₂ compounds are more suitable for high-temperature IR applications.