High temperature oxidation and γ′ depletion in the single-crystal superalloy PWA 1484

Single-crystal Ni-base superalloys are a favoured material for blades in the hot section of aero turbines. These materials exhibit excellent dimensional stability, deformation response and oxidation behaviour at higher temperatures, relative to other metals. Due to the high service temperatures and fluctuating loads experienced by turbine blades, a complete understanding of the material's oxidation and.' depletion kinetics is sought to characterise this aspect of the material's deformation response. This work provides the results and subsequent analysis of stress-free gamma' depletion tests performed on the single-crystal Ni-base superalloy PWA 1484. It was determined that the gamma' depletion kinetics of this material followed a sub-parabolic rate law. Furthermore, gamma' depletion kinetics were dependent upon surface roughness. Surface roughness can be an issue in practical application of oxidation principles and data. A relationship is developed, based on the literature and current work, which relates the stress-free gamma' depletion kinetics to exposure temperature, time and surface roughness.