ISSN:
1573-4889
Keywords:
Nb-modified Ti3Al
;
combustion gas
;
hot corrosion
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The corrosion behavior of a Nb-modified Ti3Al intermetallic compound containing 11 at.% Nb in a simulated combustion gas with and without deposits of a Na2SO4−NaCl mixture was examined at 600–800°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°C, after which the reaction stopped. A more important and longlasting effect was observed instead at 800°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 TiO2), an intermediate region of a mixture of variable composition of oxides of the three metals, and a TiO2-rich layer beneath it. At 800°C the scales tended to form a thin, discontinuous Al2O3-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°C is attributed to the appearance of sulfides in the inner region of the scale and to a more efficient scale fluxing.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01046757
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