Effects of annealing treatment on the corrosion properties of IN625 produced by additive manufacturing technique using different scanning texture

This investigation examines nickel-chromium (Ni-Cr) based alloys, recognized for their exceptional performance characteristics, particularly outstanding corrosion resistance and elevated temperature stability. These materials serve critical roles in aerospace applications, extensively utilized in essential components including engine parts and exhaust systems. Specimens examined were manufactured using Laser Powder Bed Fusion (LPBF), an advanced additive manufacturing process employing laser beams to selectively melt metal powder in successive layers following complex geometrical patterns. The primary objective is to investigate Inconel 625 corrosion behavior under varying thermal conditions in non-aggressive environments. Specimens underwent annealing heat treatment to relieve residual stresses from the additive manufacturing process. Subsequently, comprehensive surface passive layer analysis was conducted through various electrochemical techniques: Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PD), and Mott-Schottky (MS) measurements. Testing was performed in borate buffer solution to evaluate how thermal variations affect passive film integrity and protective performance. Results demonstrate that chromium-containing alloys develop protective passive layers functioning as barriers, limiting alloying element diffusion. However, when compromised through high-temperature exposure, nickel can diffuse through the degraded film and reach the surface, forming nickel oxides. Findings also highlight laser scanning strategy importance for subsequent treatments. Only NP180 and STRIPES demonstrated improvement following high-temperature heat treatment, while CHESS and NP maintained existing behavior or deteriorated.