The corrosion of Nb-modified Ti{sub 3}Al in a combustion gas with and without Na{sub 2}SO{sub 4}-NaCl deposits at 600-800{degrees}C
- Corrosion Science Lab., Shenyang (China)
- Instituto di Chimica, Genova (Italy); and others
The corrosion behavior of a Nb-modified Ti{sub 3}Al intermetallic compound containing 11 at.% Nb in a simulated combustion gas with and without deposits of a Na{sub 2}SO{sub 4}-NaCl mixture was examined at 600-800{degrees}C for times up to four days. In the absence of salt deposits the corrosion rates were rather low and increased only slightly with temperature, producing very thin scales of mixed oxides of Ti, Al, and Nb without sulfides. The presence of the salt deposits produced higher weight gains during an initial stage of one to two days at 600 and 700{degrees}C, after which the reaction stopped. A more important and long-lasting effect was observed instead at 800{degrees}C, when the kinetics of hot corrosion became nearly linear. The scales formed by hot corrosion were complex mixtures of various corrosion products at all temperatures and showed a porous outer region containing a mixture of unreacted salts with oxides (mainly TiO{sub 2}), an intermediate region of a mixture of variable composition of oxides of three metals, and a TiO{sub 2}-rich layer beneath it. At 800{degrees}C the scales tended to form a thin, discontinuous Al{sub 2}O{sub 3}-rich layer in the middle and contained an additional innermost region presenting a large concentration of sulfur, very likely as Nb and Ti sulfides. The high rate of hot corrosion at 800{degrees}C is attributed to the appearance of sulfides in the inner region of the scale and to a more efficient scale fluxing.
- OSTI ID:
- 96436
- Journal Information:
- Oxidation of Metals, Journal Name: Oxidation of Metals Journal Issue: 5-6 Vol. 42; ISSN OXMEAF; ISSN 0030-770X
- Country of Publication:
- United States
- Language:
- English
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