Abstract: Fe based amorphous / nanocrystalline (Fe-Cr-B-P-C) composite coatings were synthesized by high velocity oxy-fuel (HVOF) thermal spraying with different powder feed rates on the mild steel substrate. The microstructural characterization of the composite coatings revealed presence of embedded nanocrystalline phases in the amorphous matrix. The amorphous phase fraction increased, whereas the porosity content followed a descending trend with the increment in powder feed rate during the spraying process. The combined effect of extent of devitrification and porosity content on the corrosion behavior of the various coatings was analysed in a saline environment. The enhanced corrosion resistance of the HVOF sprayed Fe-based composite coating is ascribed to the lower porosity content and retained amorphous phase. In addition, the presence of chromium hydroxide along with some of the oxides and hydroxides of iron in the protective film helps in inhibiting the corrosion process.
Authors: Sapan K. Nayak, Anil Kumar, Kuntal Sarkar, Abhishek Pathak, Atanu Banerjee, and Tapas Laha
Keywords: High velocity oxy-fuel (HVOF) spraying, Fe-based amorphous/nanocrystalline composite coating, Corrosion behaviour, Polarization