Effect of Post Processing Heat Treatment on the Cyclic High Temperature Hot Corrosion Behavior of the Laser Powder Bed Fusion Processed Inconel 718

Abstract

In the present investigation, the cyclic hot corrosion behavior of laser powder bed fusion (LPBF)-processed Inconel-718 superalloy subjected to single-aging (HT-1) and double-aging (HT-2) heat treatments was systematically evaluated. Tests conducted at 850°C for 96 h in a Na2SO4-NaCl-NaVO3 molten salt environment demonstrated that HT-2 exhibited significantly enhanced corrosion resistance. The cumulative weight gain for HT-2 was 4.8 mg/cm2, compared to 5.7 mg/cm2 for HT-1 (an approximate 15.8% reduction), alongside a notably lower calculated corrosion rate (584.0 vs. 693.5 mg/cm2/year). Cross-sectional analysis indicated that HT-2 formed a thinner, denser, and more adherent oxide scale—primarily Cr2O3 and NiCr2O4 spinel—with reduced chromium depletion beneath the oxide layer. This improved corrosion resistance of HT-2 is attributed to its refined precipitate distribution and enhanced chemical homogeneity, which promote uniform chromium diffusion and the formation of a stable protective oxide barrier. This stable oxide scale effectively limits oxygen ingress, molten salt penetration, and scale spallation during cyclic thermal exposure. Overall, optimized double-aging significantly enhances the cyclic hot corrosion resistance of LPBF-processed Inconel-718. These findings provide important insights into tailoring post-processing heat treatments to improve the high-temperature durability of additively manufactured superalloys.