Effect of pack characteristics and process parameters on the properties of aluminide-coated Inconel 625 alloy

Abstract In this study, Inconel 625 alloy was initially aluminide coated by halide-activated pack cementation at 700 °C for 4 h using fine (40–45 µm) globular and coarse (10–75 µm) ligament aluminum particles. Microstructural features and hardness variation of the coatings along with their oxidation behavior at 1000 °C during 50 h were investigated to reveal the effect of pack characteristics on the properties. Investigations revealed that (i) a homogeneous and continuous coating layer was formed on the surface without internal oxidation, (ii) a thicker coating (∼60 µm) was formed due to the pack consisting of coarse particles, (iii) a higher hardness value (1369 HV0.5) was measured for the coated alloy using fine particles in the pack, and (iv) the coating with coarse powder exhibited higher oxidation resistance during the first 50 h of oxidation test period. Secondly, superalloy was coated at different temperatures (700 and 1000 °C) and times (2 and 4 h) using coarse particles. In this stage, the findings showed that by increasing process temperature and time, the accumulation of aluminum on the superalloy surface increased and the oxidation tendency remained at a lower level in coatings containing thicker layers.