Fabrication and corrosion resistance of HVOF-sprayed Ni2Si intermetallic compound

► Ni2Si intermetallic coatings were produced by HVOF spraying. ► A bulk Ni2Si was used as a reference for corrosion tests in 70% H2SO4. ► Corrosion rate of HVOF coatings was much lower than that of substrate. ► Both HVOF Ni2Si and bulk Ni2Si showed active–passive behavior. ► There was a small performance gap between coating and reference material. In this study, Ni2Si powders were deposited onto 420 stainless steel substrate using high velocity oxy-fuel (HVOF) process. The coatings were characterized by X-ray diffractometery, optical and scanning electron microscopy and microhardness measurements. Tafel polarization tests and electrochemical impedance spectroscopy (EIS) measurements were employed to study corrosion performance of the coatings in 70% H2SO4 media at room temperature. Here, a dense sintered Ni2Si was used as reference material. The results showed the phase composition of HVOF coating is similar to that of feedstock powders. The corrosion rate of HVOF Ni2Si coatings was much lower than that of 420 stainless steel substrate but slightly higher than that of bulk Ni2Si. Further investigation showed that both thermally sprayed and sintered (reference) Ni2Si alloys exhibited similar anodic polarization behavior including a narrow active section followed by a wide passive region.