Oxidation behaviors and compressive strength evolution of DD6 Ni-based single-crystal superalloy at 1100 ℃

In this work, the oxidation behaviors of DD6 Ni-based single-crystal superalloy and its compressive strength evolution after oxidation were investigated. The results showed that the thermal exposure time has a significant effect on the oxidation products, oxidation kinetics, Al elements diffusion and compressive strength evolution of DD6 superalloy. Firstly, the relationship between grain size change of (Ni_0.9,Co_0.1)O, the thickness of γ′-free zone and the exposure time was approximate power exponential law, while the relationship between weight change of DD6 superalloy and exposure time was approximate parabolic law since the densification of inner continuous Al₂O₃ layers hindered the diffusion of oxygen ions. Moreover, the black phases of AlN in the γ′-free zone formed during the oxidation process, and its quantity and size increased first and then decreased with the oxidation time extending, since the inner Al₂O₃ not only blocked the ion but also reacted with AlN. In addition, with the increase of oxidation time, the compressive yield strength of DD6 in [001] direction first decreased rapidly and then gradually stabilized at about 740 MPa.