Interfacial reactions of a MAX phase/superalloy hybrid

Oxidation resistant, strain tolerant MAX phase coatings are of general interest for high temperature applications. Accordingly, Cr 2 AlC MAX phase coupons were vacuum diffusion bonded to an advanced turbine disk alloy at 1100 °C for compatibility studies. The interface revealed an inner diffusion zone consisting of ~10 µm of β‐Ni(Co)Al, decorated with various γ′ (Ni,Co) 3 Al, Ta(Ti,Nb)C, and W(Cr,Mo) 3 B 2 precipitates. On the Cr 2 AlC side, an additional ~40‐µm Al‐depletion zone of Cr 7 C 3 formed an interconnected network with the β‐Ni(Co)Al. On the superalloy side, enhanced carbide precipitation developed over a depth of ~80 µm. Subsequent annealing for 100 h and 1000 h at 800 °C coarsened some features, enhanced TCP precipitation in the superalloy, but only enlarged the diffusion layers by ~5 µm at most. Because of Al depletion from the MAX phase and corresponding Al enrichment of the alloy, the reaction zone displayed similarities to an oxidized Cr 2 AlC surface and an aluminized superalloy, respectively. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.