High temperature corrosion performance of Inconel 625 hard overlays deposited on stainless steel substrate

Abstract

In elevated conditions, austenitic stainless steels suffer intense damage by corrosion because of the severe oxide scale development. Giving stainless steel a corrosion-resistant surface coating can prevent excessive damage. In this case, welding-based overlaying is a potential method to restore the damaged parts as it has a higher productivity rate. This investigation articulates the corrosion resistance behavior of the multiple overlapped Inconel 625 (IN625) weld overlays on the AISI 316L substrate plate. The corrosion resistance at elevated temperatures was investigated with kinetic curves, further revealing the corrosion products from the sample surface. Characterization techniques like scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and Raman spectroscopy were employed to analyze the corrosion products. Hot corrosion kinetics in the molten salt environment (Na₂SO₄ + V₂O₅) revealed that the IN625 overlay samples gained a weight of 40.15 mg/cm², and the substrate had a weight gain of 65.42 mg/cm². From the hot oxidation kinetics, it is evident that the mass gained by the substrate is more than twice that of the Inconel overlay sample. Furthermore, the formation of oxides and spinel phases rich in nickel (NiO, NiCr₂O₄) highly influenced the corrosion kinetics of the multiple overlapped IN625 overlay sample. The AISI 316L substrate sample revealed the existence of critical oxide phases such as Fe₂O₃ and Cr₂O₃, which were lesser and did not influence the corrosion resistance at 900°C. In the present investigation, the multiple overlapped IN625 weld overlay offered excellent corrosion resistance at high temperature compared to the AISI 316L.