A study in the influence of HVOF parameters on the hot- corrosion behaviour of NiCrAlY coatings

In this investigation، NiCrAlY coatings were deposited on steel substrate using the HVOF process. Different spray parameters were applied such as Propane flow rate، spray distance and powder feed rate. The hot corrosion behavior of resulted samples was studied in salt mixture Na2SO4-60%V2O5 at 900˚C for 30 min to 22 h in an ambient atmosphere. After hot corrosion tests the microstructure and phase composition of these coatings were analysed using Optical microscope، Scanning electron microscopy/Energy dispersive spectroscopic analysis (SEM/ EDS)، and X-ray Diffraction (XRD) techniques. The analysis of the results indicates that the parameters variation have a significant effect on the properties of NiCrAlY coatings، especially on the oxide phase content present in the coating، and therefore on the hot corrosion resistance of this coating. It was observed that coating prepared by 60 lit/min Propane flow rate، 300 lit/min Oxygen flow rate، 20 cm spray distance and 32 gr/min powder feed rate has the best corrosion resistance، because of the smaller oxide contents inside the coating.