Bonding and oxidation protection of Ti${_2}$AlC and Cr${_2}$AlC for a Ni-based Superalloy

TL;DR

This study investigates the bonding behavior and oxidation resistance of Ti2AlC and Cr2AlC MAX phases with a Ni-based superalloy, demonstrating Cr2AlC's potential as an oxidation barrier at high temperatures.

Contribution

It provides new insights into the bonding conditions and oxidation protection capabilities of Ti2AlC and Cr2AlC MAX phases with Ni-based superalloys.

Findings

Cr2AlC forms a good diffusion bond with Ni-based superalloy at 1000°C and 2 MPa.

Ti2AlC requires higher temperature and pressure for bonding and is a poor oxidation barrier.

Cr2AlC effectively prevents oxidation of Inconel-718 after thermal cycling.

Abstract

Alumina forming, oxidation and thermal shock resistant MAX phases are of a high interest for high temperature applications. Herein we report, on bonding and resulting interactions between a Ni-based superalloy, NSA, and two alumina forming MAX phases. The diffusion couples Cr${_2}$AlC/Inconel-718/Ti${_2}$AlC were assembled and heated to 1000 or 1100{\deg}C in a vacuum hot press under loads corresponding to stresses of either 2 MPa or 20 MPa. The resulting interfaces were examined using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Good bonding between Cr${_2}$AlC and NSA was achieved after hot pressing at 1000{\deg}C and a contact pressure of only 2 MPa; in the case of Ti${_2}$AlC a higher temperature (1100{\deg}C) and pressure (20 MPa) were needed. In both cases, a diffusion bond was realized with no evidence of interfacial damage or cracking after cooling to room temperature. Twenty thermal cycles from room temperature to 1000{\deg}C showed that Ti${_2}$AlC is a poor oxidation barrier for Inconel-718. However, in the case of Cr${_2}$AlC no cracks, delamination nor surface degradation were observed, suggesting that this material could be used to protect Inconel-718 from oxidation.