Life enhancement of NASA’s space shuttle main engine-main combustion chamber liner by high energy beams

Abstract

Microstructure of wrought, laser and electron beams processed NARloy-Z (Cu-3 wt. % Ag-0.5 wt. % Zr) was investigated for thermal stability at elevated temperatures (539 - 760°C) for exposures up to 94 hours. Optical, scanning electron microscopy and electron probe microanalysis were employed for studying microstructural evolution and kinetics of precipitation. Grain boundary precipitation and precipitate free zones (PFZ’s) were observed in the wrought alloy after exposure to temperatures above 605 °C. The fine-grained microstructure observed in the laser and electron beam processed NARloy-Z was more stable at elevated temperatures. Microstructural changes correlated well with hardness measurements and mechanical properties.Microstructure of wrought, laser and electron beams processed NARloy-Z (Cu-3 wt. % Ag-0.5 wt. % Zr) was investigated for thermal stability at elevated temperatures (539 - 760°C) for exposures up to 94 hours. Optical, scanning electron microscopy and electron probe microanalysis were employed for studying microstructural evolution and kinetics of precipitation. Grain boundary precipitation and precipitate free zones (PFZ’s) were observed in the wrought alloy after exposure to temperatures above 605 °C. The fine-grained microstructure observed in the laser and electron beam processed NARloy-Z was more stable at elevated temperatures. Microstructural changes correlated well with hardness measurements and mechanical properties.