Microstructural and Electrochemical Corrosion Characterization of a Novel 50 IN-50 Co Super Alloy Composite in 3.5wt.% NaCl Solution

A novel 50% Inconel-50% cobalt (50 IN-50 Co) superalloy composite was developed via an advanced powder metallurgy spark plasma sintering (SPS) technique. The microstructural characteristics and electrochemical corrosion behavior of the composite were extensively studied to reveal its potential for industrial applications that demand excellent corrosion resistance properties. Field emissions scanning electron microscopy (FESEM) revealed a homogeneous distribution of IN718 and Co212 alloys within each other, with good interfacial integrity free of secondary phases, reaction products, or voids. X-ray diffraction (XRD) analysis revealed characteristic peaks corresponding to the pure IN718 and Co212 alloys, respectively, affirming successful composite formation without any secondary phases. Electrochemical corrosion tests, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and cyclic potentiodynamic polarization (CPDP), were conducted to assess the alloy's corrosion resistance. Results demonstrated that the 50 IN-50 Co composite exhibited a substantial enhancement in corrosion resistance, with a charge transfer resistance (Rct) approximately 378% higher than pure IN718 and 123% higher than Co212, along with a polarization resistance (Rp) approximately 36% higher than both IN718 and Co212. The composite's superior corrosion resistance is attributed to an effective passive film formation and enhanced charge transfer resistance. LPR measurements corroborated these findings, with the alloy demonstrating the lowest corrosion current density and the highest polarization resistance. CPDP curves indicated a lower current density and a more comprehensive passivation potential range, suggesting effective surface passivation and reduced pitting susceptibility. These findings highlight the promising potential of the superalloy composite for diverse industrial applications in harsh and corrosive environments. This detailed characterization offers crucial insights for newly developed alloys with customized corrosion resistance, which is essential for use in challenging industrial and engineering environments.