Investigation of Corrosion Response of Spark Plasma Sintered Ni-9Fe-22Cr-10Co Superalloy in Sulphuric Acid Environment

Abstract

It has been established over the years that Nickel-based superalloys are very difficult to manufacture as a result of the combination of various elemental composition. In this study, elemental powders of Ni-9Fe-22Cr-10Co wt.% superalloys were synthesized via spark plasma sintering technique at sintering temperatures ranging from 850 to 1100 °C with holding time, heating rate and pressure of 5 min, 50 °C/min and 50 MPa. The microstructural analyses were performed using an optical microscopy and scanning electron microscopy equipped with energy dispersive spectroscopy, while phase analyses were carried out using X-ray diffractometry. The potentiodynamic polarization tests were performed in 1M H2SO4 solution at ambient temperature. Results obtained show that the densification of the alloys increased with increasing sintering temperature with optimum results obtained at a sintered temperature of 1000 °C corresponding to sintered density of 98%. Furthermore, the morphologies of the sintered compacts reveal homogenous dispersion of elemental composition with less morphological defects obtained at 1000 °C. For corrosion analysis, all sintered samples display passivation region with few fluctuations. However, sample sintered at the 1000 °C yielded more stable passivity with corrosion rate of 0.0181 mm/year.