Comparison of Recuperator Alloy Degradation in Laboratory and Engine Testing

In order to increase the efficiency of advanced microturbines, durable alloy foils are needed for their recuperators to operate at $650–700°C$⁠. Prior work has demonstrated that water vapor in the exhaust gas causes more rapid consumption of Cr from austenitic alloys, leading to a reduction in lifetime for the thin-walled components in this application. New commercial alloy foils are being tested in both laboratory tests in humid air and in the exhaust gas of a modified $60kW$ microturbine. Initial results are presented for a commercial batch of $80μm$ alloy 120 foil. The Cr consumption rates in laboratory testing were similar to those observed in previous testing. The initial results from the microturbine indicate a faster Cr consumption rate compared to the laboratory test, but longer term results are needed to quantify the difference. These results will help to verify a Cr consumption model for predicting lifetimes in this environment based on classical gas transport theory.