Comparison of the High-Temperature Oxidation Behavior of Cr2AlC MAX Phase and CoNiCrAlY Compounds

Abstract

In this work, Cr2AlC samples with different purities were made by the spark plasma sintering (SPS) technique, and the effect of undesired Cr7C3 phase on the high-temperature oxidation performance at 1000 °C was examined. Also, the oxidation resistance of this MAX phase was compared with an oxidation-resistant CoNiCrAlY sample which was prepared with the SPS method. The results of oxidation tests after 200 h showed that the Cr2AlC sample with the lowest content of the Cr7C3 has better oxidation resistance than CoNiCrAlY sample. Exanimating the oxidation kinetics of Cr2AlC samples showed that these samples follow a near-cubic law, while the CoNiCrAlY sample follows parabolic kinetics. Microstructural studies showed that the oxide layer in the MAX phase samples grows uniformly and consists of the Al2O3 and Cr7C3, whereas in the CoNiCrAlY compound this layer has a non-uniform growth and it contains Al2O3 and spinel oxide phases. High variation in volume and stress was created through the non-uniform growth of the oxide layer in the CoNiCrAlY sample which leads to the creation of defects such as microcracks.