High temperature stress-rupture characteristics of mo and some mo alloys

Abstract

The stress-rupture characteristics of unalloyed molybdenum at 2200°C were experimentally determined to be dependent on whether it is arc-cast or wrought sintered material. Three vendor sources of arc-cast molybdenum gave identical results whereas two sources of wrought sintered molybdenum gave results which were different from each other and different from the results for arc-cast molybdenum. The differences are attributed to the differences in grain size. The arc-cast material has huge grains (500^ to 900/x) whereas the wrought sintered material has relatively fine grains (25/z to 50/i) even after 100 hours at 2200°C. Stress-rupture curves for arc-cast molybdenum from 1600° to 2400 °C are presented as well as a plot of stress vs the Larson-Miller parameter. The constant in the L-M expression is determined to be 13.4. Also presented are the stress-rupture data for arc-cast molybdenum TZM at 2000° and 2200°C. The data indicate that the increased rupture life of TZM over unalloyed molybdenum is negligible at 2200°C. The stress-rupture data for wrought sintered Mo-50Re show it to have a rupture life approximately one order of magnitude greater than that for unalloyed molybdenum at both 1600° and 2200°C.