In this paper, NaCl-induced corrosion behavior in Nb-bearing ferritic stainless steels and the effects of Cr, Si and Mo on it were clarified. The following results were obtained: 1) NaCl-induced hot corrosion was caused by oxidation. Since the grain boundary acted as a path of oxygen diffusion, the corrosion was promoted extremely by the existence of Na(+). 2) Cr2O3 formed at the surface of steels and the grain boundary by oxidation at elevated temperature reacted with Na(+) and changed to aqueous Na2CrO4. As Na2CrO4 dissolved in water at room temperatire, a Cr-depleted zone formed closely to the oxide was exposed and oxidized again. With the repetition of this process the corrosion proceeded. 3) The NaCl-induced hot corrosion property was improved by the addition of Mo. Mo, as well as Nb, precipitaed as Laves phase at elevated temperature, and the amount of Laves phase increased by the addition of Mo. Laves phase precipitated not only within the grains but also at the grain boundaries which acted as a diffusion path of O. Therefore, the corrosion property was improved by the suppression of intergranular oxidation.
Effects of alloying elements on NaCl-induced hot corrosion resistance of stainless steels
Einflüsse von Legierungselementen auf NaCl-bewirkten Heißkorrosionswiderstand von rostfreien Stählen
Review of Automotive Engineering (JSAE) ; 28 , 3 ; 417-421
2007
5 Seiten, 10 Bilder, 1 Tabelle, 12 Quellen
Article (Journal)
English
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