High-Temperature Oxidation and Hot Corrosion behavior of Selective Laser Melted IN939: Microstructural Modification and Grain Refinement via Ultrasonic Shot Peening  

This study investigates the effect of Ultrasonic Shot Peening (USSP) on the electrochemical corrosion, high-temperature oxidation, and hot corrosion resistance of Inconel 939 (IN939) alloy fabricated via Selective Laser Melting (SLM). Electrochemical corrosion tests were conducted in 3.5 wt% NaCl solution, high-temperature oxidation was performed in ambient air, and hot corrosion was evaluated under aggressive environments comprising of Na2SO4 + 25 wt% NaCl and Na2SO4 + 50 wt% V2O5 at 1000°C for 300 h. The USSP treatment significantly refined the surface grain size from 72.83 µm to 44.29 µm, leading to improved electrochemical corrosion resistance, oxidation resistance, and hot corrosion performance. Surface analysis confirmed the formation of protective oxides such as Cr₂O₃, TiO₂, NiCr₂O₄, CoCr₂O₄, and NiO. Additionally, grain refinement enhanced the microhardness of IN939 by 19.83%.