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 60 kW microturbine. Initial results are presented for a commercial batch of 80 μm 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.