ABSTRACT

Supercritical carbon dioxide offers the potential for significant efficiency increases in power generation systems. However, limited information is available on the compatibility of supercritical carbon dioxide with highly alloyed iron-base alloys and nickel-base alloys. These alloys are designed to have good strength at elevated temperature and would likely find use in a range if power generating systems including concentrating solar power, nuclear and fossil systems.

Selected Fe- and Ni-based alloys and superalloys have been exposed in 99.995% supercritical carbon dioxide for 500 hours at 750°C and 200 bar. Post exposure examination provided information on corrosion rates, microstructural evolution and the carbon concentration in the exposed materials. Studies show relatively low corrosion rates in almost all alloys studied after 500 h of exposure but an apparent increase in carbon content even in nickel-base alloys.

INTRODUCTION

Supercritical carbon dioxide (sCO2) as a heat transfer medium offers the potential of a significant improvement in efficiency in many energy-related applications including advanced turbomachinery.1-7

This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow other to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

However, the possibility of severe oxidation and corrosion of metallic alloys in sCO2 is a concern, particularly at the elevated temperatures where it is proposed these systems would operate to achieve higher efficiencies. This study was conducted to extend the data base for materials that would be considered for turbine, compressor and high-pressure housing applications, with particular emphasis on nickel-base alloys.

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