The Effect of Heat Treatment and Build Orientation on the Susceptibility of Laser Powder Bed Fusion Additively Manufactured Alloy 625 to Crevice Corrosion

The objective of this study was to determine the optimal heat treatment and build orientation to minimize the susceptibility of additively manufactured (AM) alloy 625 to crevice corrosion. To accomplish this, metal-to-metal and acrylic-to-metal remote crevice assembly (RCA) experiments were carried out for as made (NT) AM, stress relieved (SR) AM, solution annealed (SA) AM, and solution plus stabilization annealed (SSA) AM alloy 625 in two different build orientations. Current vs. time data from metal-to-metal RCA experiments were analyzed using a commercially available statistical analysis software that was used to perform Analysis of Variance (ANOVA). While there was a lack of statistical evidence build orientation has an effect on crevice corrosion susceptibility, there was strong evidence heat treatment affects crevice corrosion susceptibility. Specifically, according to Tukey’s Multiple Comparison, alloys that were heat treated had a statistically significant lower charge passed as compared to the NT specimens. This finding was consistent with measured penetration depth where NT AM specimens had the largest maximum penetration depth. In contrast, acrylic-to-metal RCAs were used to calculate crevice corrosion current density (rate) and repassivation potential. While current densities for the AM materials were comparable, the lateral motion of the active crevice corrosion front on the NT and SR specimens was found to be slow in comparison, resulting in high damage accumulation locally. Both metal-to-metal and acrylic-to-metal RCA results are discussed within the context of non-homogenized microstructures associated with AM.