Elevated-Temperature Corrosion of CoCrCuFeNiAl0.5Bx High-Entropy Alloys in Simulated Syngas Containing H2S
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High-entropy alloys are formed by synthesizing five or more principal elements in equimolar or near equimolar concentrations. Microstructure of the CoCrCuFeNiAl0.5Bx (x = 0, 0.2, 0.6, 1) high-entropy alloys under investigation is composed of a mixture of disordered bcc and fcc phases and borides. These alloys were tested gravimetrically for their corrosion resistance in simulated syngas containing 0, 0.01, 0.1, and 1 % H2S at 500 °C. The exposed coupons were characterized using XRD and SEM. No significant corrosion was detected at 500 °C in syngas containing 0 and 0.01 % H2S while significant corrosion was observed in syngas containing 0.1 and 1 % H2S. Cu1.96S was the primary sulfide in the external corrosion scale on the low-boron high-entropy alloys, whereas FeCo4Ni4S8 on the high-boron high-entropy alloys. Multi-phase Cu-rich regions in the low-B high-entropy alloys were vulnerable to corrosive attack.
KeywordsSulfidation High-entropy alloys Syngas
The authors wish to thank Prof. Jien-Wei Yeh of National Tsing Hua University in Taiwan and Prof. Peter Liaw of University of Tennessee for providing the high entropy alloy samples. The authors also thank Joe Tylczak for the use of the SECERF facility at NETL for performing the exposure tests, Paul Danielson for metallographic preparation of samples, David Smith for XRD analysis, and Dr. Kirk Gerdes for gas exchange rate calculations. This technical effort was performed in support of ongoing research at NETL under the RES contract DE-FE0004000.
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
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