Effect of simulated earth reentry exposure on mechanical properties of several oxide dispersion strengthened and superalloy sheet materials

The effects of simulated multiple reentry into the Earth’s atmosphere on the mechanical properties of several high temperature metallic sheet materials were evaluated. The materials included five thin gage (nominally 0.025 or 0.037 cm) oxide dispersion strengthened (ODS) alloys and two thin gage (nominally 0.037 cm) superalloys. Multiple reentry conditions were simulated through cyclic Plasma Arc Tunnel (PAT) exposure. PAT exposure generally consisted of 100 cycles of 600 s duration at 1255, 1366, or 1477 K in a Mach 4.6 airstream with an impact pressure of nominally 800 N/m². PAT exposure generally produced a uniform oxide scale, oxide pits or intergranular oxidation, Kirdendall porosity, and alloy depletion zones except for the aluminum containing ODS alloys. Only a uniform oxide scale was formed on the aluminum containing ODS alloys. In some cases, the oxide scales contained copper, apparently from the PAT electrodes, thus PAT exposure may not be truly representative of reentry. Within the limits of the PAT exposures evaluated in this study, PAT exposure did not significantly affect the mechanical properties of the thin gage alloys evaluated. Thus, it appears that the microstructural changes produced by Plasma Arc Tunnel exposure have little influence on mechanical properties. He is currently on leave of absence from the Lewis Research Center and is at Der Deutschen Forschung-und Versuchsanstalt für Luft-und Raumfahnt (DFVLR) Cologne, West Germany.