Abstract
Alloy 903 (FeNiCo+Nb) is currently used for certain
components in industrial gas turbines for low coefficient of
thermal expansion applications. A variance in creep behavior
for material quality control evaluations suggested a possible
effect of moisture level on stress rupture properties. To
investigate the role of water vapor on the creep properties of
alloy 903, controlled laboratory experiments were conducted
at 650°C with 0 to 100% relative humidity. The water content
was controlled by flowing dry air through a water bath at a
constant temperature. A significant decrease of lifetime was
observed in the presence of water vapor, which is likely related
to grain boundary embrittlement by the inward diffusion of
hydrogen. The increase of the microstructure grain aspect
ratio by different forging processes generally improved the
rupture lifetime and elongation in air. However, all
specimens had reduced lifetime in the presence of water vapor
despite the microstructure grain aspect ratios.
