Influence of powder feed rate and fuel/oxygen ratio in HVOF on the electrochemical corrosion behaviour of NiCr coatings

In the present study، NiCr coating was created by the High Velocity Oxy-Fuel (HVOF) thermal spray technique under different conditions in respect to powder feed rate and fuel/oxygen ratio on the steel samples. Electro chemical corrosion behaviour of the NiCr coated samples was investigated by the potentiostatic polarization in NaCl 3. 5% solution. In order to determine the structural traits of the coatings، scanning electron microscopy (SEM/EDX) was used before and after the corrosion testing. The analysis of the results indicates that the fuel/oxygen and the powder feed rate have a significant effect on the porosity،existing oxide phases، and corrosion resistance، and un/melted powders of these coatings. corrosion behaviour of the sample، which has coated by fuel/oxygen of 1. 25 and powder feed rate of 18 gr/min، is the best due to lower porosity and oxide zones.