A Taylor Expansion Model Approach to Aluminide Evolution and High-Performance Surface Behavior in Hastelloy C-276

Abstract

This study investigates the aluminizing kinetics of Hastelloy C276 alloy and evaluates how aluminizing enhances the surface properties of this superalloy. Pack aluminizing was performed on Hastelloy C276 specimens for 2, 4, and 6 h at 600 degrees C, 650 degrees C, and 700 degrees C. SEM observations showed the formation of compact and dense aluminide coatings. According to the XRD analyses, two aluminide phases were indentified (Ni2Al3 and Ni3Al). Ni2Al3 predominates near the coating's outer surface, whereas Ni3Al is concentrated closer to the substrate/coating interface due to lower local aluminum activity. For kinetic studies, the Taylor expansion (TE) model was implemented under a transient diffusion regime to assess the Al diffusion coefficients in the bi-phased aluminized layer. The Al activation energy for Hastelloy C276 was deduced and confronted with the literature results. And the activation energy for Al diffusion in the Hastelloy C-276 alloy was calculated to be 65.26 kJ & centerdot;mol(-1) with the Taylor expansion (TE) model; furthermore, the mass gain per unit associated with the formation of aluminides coating was also evaluated. In the wear experiments performed, it was determined that the application of aluminizing increased the durability of the surfaces and reduced wear losses.