Isothermal oxidation behavior of a Cr-modified aluminide coating on a Ni-based superalloy

Currently, Ni- based superalloys are widely applied to turbine blades or other components of gas turbines for their excellent high temperature mechanical properties. These components must exhibit a high level of resistance to the oxidation and corrosion conditions generated by the combustion environment. The general design philosophy is to select a high strength substrate alloy to withstand the stress and apply a surface coating to give maximum protection from the environment. In this work, a Cr-modified aluminide (Al-Cr) coating were prepared by combining arc ion plating and pack cementation aluminizing. As a contrast, a simple aluminide coating was developed by pack cementation aluminizing. The isothermal oxidation behaviors at 1000 and 1100 ℃ were investigated on the Ni-based superalloy DSM11 substrate, aluminide coating and Al-Cr coating. The results demonstrate that aluminide coating and Al-Cr coating are dense and adhere tightly to the substrate. The microstructures of aluminized
coating and Al-Cr coating are divided in two distinguished areas: the outer layer and the interdiffusion zone. The outer layer of the aluminized coating is composed of b-NiAl and Ni2Al3 phases, while the Al-Cr coating consists of b-NiAl, Ni2Al3, a-Cr and AlCr2 phases. The DSM11 substrate shows bad oxidation behavior at 1000 ℃ isothermal oxidation test. The aluminide coating and Al-Cr coating both possess good oxidation properties in this test. Compared with aluminide coating, Al-Cr coating exhibits much better oxidation behavior due to the formation of Cr