The oxidation behavior of tungsten and germanium alloyed molybdenum disilicide coatings

Conference · Fri Nov 01 00:00:00 EST 1991

OSTI ID:10122274

Mueller, A; Wang, Ge; Rapp, R A ^[1]; Courtright, E L ^[2]; Kircher, T ^[3]

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1. Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering
2. Pacific Northwest Lab., Richland, WA (United States)
3. Naval Air Development Center, Warminster, PA (United States). Aerospace Materials Div.

A two-step coating process was used to produce a (Mo,W)(Si,Ge){sub 2} coating on niobium. After exposure to high temperatures, a lower silicide layer forms underneath and is effective in arresting cracks. The oxidation weight-gain kinetics are parabolic following an initial transient period. Test coupons coated with (Mo,W)(Si,Ge){sub 2} passed 200 one-hour cycles at 1370{degree}C and 60 one-hour cycles at 1540{degree}C. These results, along with evidence of a thick protective glass layer, suggest that the germanium additions help cyclic oxidation resistance. The beneficial effects of the tungsten include the formation of microvoids, which provides a lower effective elastic modulus, and mechanical strengthening. No accelerated low temperature or ``pest`` oxidation was observed in the temperature range between 500--700{degree}C. Thus, a (Mo,W)(Si,Ge) multicomponent silicide coating offers significant promise for the protection of Nb-base alloys exposed to cyclic oxidizing environments over a broad range of temperatures.

• Research Organization: Pacific Northwest Lab., Richland, WA (United States)
• Sponsoring Organization: Department of Defense, Washington, DC (United States)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 10122274
• Report Number(s): PNL-SA-20049; CONF-9111115-3; ON: DE92006509
• Resource Relation: Conference: High temperature structural silicides workshop,Gaithersburg, MD (United States),4-6 Nov 1991; Other Information: PBD: Nov 1991
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MOLYBDENUM SILICIDES
OXIDATION
NIOBIUM
DIFFUSION COATINGS
TUNGSTEN
GERMANIUM
LAYERS
X-RAY DIFFRACTION
MICROSTRUCTURE
360205
360105
CORROSION AND EROSION