Compatibility of molybdenum with high temperature hydrogen

Abstract

Arc-cast Molybdenum samples were exposed to a high temperature (2200–2630 K) hydrogen (H2) environment at ∼1 atm to evaluate their chemical compatibility under extreme temperature conditions; this compatibility information is useful to examining the potential application of Mo-matrix cermets for nuclear thermal propulsion applications. Subscale samples were exposed to 1–2 L/min of flowing H2 with hold times of 80 min at temperature (2200–2630 K). The measured mass loss was observed to be slightly lower than that predicted by vapor pressure calculations, which indicates minimal chemical corrosion reactions between Mo and H2 up to temperatures in excess of 90% of the melting temperature of Mo. Grain size dramatically increases across the temperature range. Parallel surface ledges within grains are frequently observed across the sample surface following high temperature hydrogen exposure and in general are related to the orientation of the grain. The observed mass loss is sufficiently low to consider Mo cermets as a candidate fuel for NTP applications.