OXIDATION BEHAVIOR AND PROTECTIVE COATINGS FOR COLUMBIUM AND COLUMBIUM-BASE ALLOYS
Available information on the oxidation behavior of and protective coatings for Nb and Nb-base alloys is summarized and discussed. Unalloyed Nb forms a tarnish film and reacts parabolically with air or oxygen up to about 450 deg C. In this temperature range the protective film blisters and unprotective, white Nb/sub 2/O/sub 5/ forms. Oxidation behavior is linear after formation of Nb/sub 2/O/sub 5/, the rate increasing appreciably with increasing temperature. NbO/sub 5/ is solid to 1500 deg C. Binary additions which improve the oxidation resistance include Ti, Zr, Mo, W, Cr, and V. Ti and Zr also improve the contamination resistance of Nb. Ternary and higher alloying produces further significant improvements in oxidation behavior by promoting formation of complex oxide scales. Several of the best systems are Nb-Cr-Al, Nb- Fe-Al, Nb-Mo-Al, Nb- Ti-Al, and Nb-Ti-Cr, improvements up to 1000-fold over unalloyed Nb are possible, but the most oxidation-resistant alloys are unfabricable. lnformation on protective coatings for Nb is limited. The best coatings to date appear to be a duplex LM-5 coating and a modified Ni-C coating. (auth) The corrosion behavior of 75A titanium in water-diluted and undiluted mixtures of reagent-strength nitric and hydrochloric acids has been investigated. These tests were at boiling temperatures in the immersed and vapor phases, The possibilities of hydrogen embrittlement and stress corrosion under test conditions were also investigated, Titanium weld studies were included. These tests were duplicated with Nichrome V present in the solution. (auth)
- Research Organization:
- Battelle Memorial Inst. Defense Metals Information Center, Columbus, Ohio
- NSA Number:
- NSA-14-011926
- OSTI ID:
- 4172746
- Report Number(s):
- DMIC-123; PB-151080
- Country of Publication:
- United States
- Language:
- English
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