Session: 18-06: Metallurgy, Coating, & Repair

Paper Number: 152135

Environmental Resistance of High Entropy Alloys: Impact of Downstream Hydrogen Combustion on Oxidation Resistance 

The transportation industry, a major contributor to global greenhouse gas emissions, is actively pursuing decarbonization through the adoption of carbon-free fuels such as hydrogen. While hydrogen is a promising fuel alternative thanks to its primary combustion product being steam as opposed to CO₂, there are concerns about the effect of this increased steam content on the corrosion of hot section materials. Additionally, although it is known that hydrogen infiltration can lead to the embrittlement of metals and diffusion rates increase with temperature, few studies have been reported on the effect of high temperature hydrogen exposure on gas turbine alloys.

This study explores the environmental resistance of Al-CoCrFeNi-based high entropy alloys (HEAs) placed downstream from a combustor using hydrogen fuel. High entropy alloys are interesting candidates for gas turbine due to their heavily mismatched lattice structure leading to sluggish diffusion, which could give them superior environmental resistance. Three HEAs with different doping elements, namely Al₆Co₂₁Cr₂₁Fe₂₁Ni₃₀, Al₄Co₂₁Cr₂₁Fe₂₁Ni₃₀Ti₂, and Al₄Co₂₀Cr₂₀Fe₂₀Mo₁Ni₃₀Ti₂ (at.%), were compared against Hastelloy X in terms of oxidation, corrosion, and hydrogen absorption. Samples were placed at different locations with respect to the flame within a demonstrator hydrogen combustor cell, which was run for multiple cycles of up to 6 hours. In-situ imaging and temperature measurements continuously monitored the samples and the combustion conditions within the chamber. Ex-situ scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed the depth of oxidation and oxide species, damage caused by the high-temperature flame, and presence of hydrides. Thermogravimetric analyses were conducted to determine the hydrogen absorption and desorption behaviours of the metals prior to flame exposure and were conducted post-flame exposure to determine if any hydrogen is adsorbed by the samples during combustion using a proprietary electrochemical analytical instrument.

The results of this research highlight the consequences of burning pure hydrogen on the metals downstream of a hydrogen combustor.

Presenting Author: Anne Bastin Carleton University

Presenting Author Biography: Anne Bastin is a Ph.D. student in Mechanical Engineering at Carleton University, Ottawa, specializing in the environmental resistance of high entropy alloys for jet engines and gas turbine applications.
Collaborating closely with the National Research Council of Canada, particularly the Aerospace Research Center, she focuses her research on the oxidation performance, hydrogen embrittlement resistance, and mechanical properties of these alloys at high temperatures in hydrogen-containing environments.
In addition to her experimental work, Anne employs machine learning techniques to predict the environmental resistance of alloys, aiding in the design of more resilient materials.
She has authored publications on topics such as heat treatability, phase stability, and long-term high-temperature oxidation of high-entropy alloys.
Her work advances the development of durable materials for aerospace applications.

Authors:

Anne Bastin Carleton University
Taylor Robertson National Research Council Canada
Antoine Durocher National Research Council Canada
Patrizio Vena National Research Council Canada
Richard Kearsey National Research Council Canada
Xiao Huang Carleton University