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

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.