Microstructural changes of aluminized Alloy 617 during high-temperature aging

Abstract

In this study, aluminized Alloy 617 was prepared by Al-pack cementation of high temperature high Al activity process. The microstructure evolution and microstructural changes of aluminide coating were investigated after Al-pack cementation and high-temperature aging. The aluminide coating was composed of Ni-aluminide layers, such as delta-Ni2Al3, beta-NiA1, Cr2Al, Al3+xMo1-x, and inter-diffusion zone by pack cementation. After high-temperature aging, the aluminide coating was transformed from the delta-Ni2Al3 to the beta-NiAl because of outward Ni diffusion from substrate. The Cr2Al and the Al3+ xMo1-x were dissolved during aging. On the other hand, the alpha-(Cr, Mo) particles were precipitated during aging due to the low solubility of alloying elements in the beta-NiAl. The beta-NiAl newly formed by the outward Ni diffusion during aging and resulted in the formation of the inter-diffusion zone. The inter-diffusion zone consisted of beta-NiAl, Ni-3(Al, Ti), Cr-rich M23C6 carbide, and sigma phases.