Low temperature hot corrosionThe reaction of Co-Cr, Ni-Cr, Co-Cr-Al, and Ni-Cr-Al alloys with Na2SO4 in the presence of SO3 at temperatures between 700 and 750 C leads to the formation of liquid CoSO4-Na2SO4 or NiSO4-Na2SO4 deposits on the alloy surface. The formation of Cr2O3 and/or Al2O3 below this deposit results in a locally low P(O2) and a higher P(S2) and P(SO2). It is noted that these conditions can prevent protective oxide formation either by sulfide formation in the alloy, which localizes the Cr and/or Al in discrete particles, or by acid fluxing involving a reaction between Al2O3 or Cr2O3 and SO2 to form a salt-soluble species and subsequent reprecipitation as porous oxides in regions of higher P(O2). These processes may occur simultaneously, although a given alloy generally exhibits features of predominantly one type. Here, the Ni-Cr and Ni-Cr-Al alloys, and to some extent the Co-Cr alloys, exhibit features indicative of the sulfidation mechanism, whereas the morphology for the Co-Cr-Al alloy is more consistent with a predominant acid fluxing mechanism.
Document ID
19830061034
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Chiang, K. T. (Pittsburgh Univ. Pittsburgh, PA, United States)
Pettit, F. S. (Pittsburgh Univ. Pittsburgh, PA, United States)
Meier, G. H. (Pittsburgh, University Pittsburgh, PA, United States)
Date Acquired
August 11, 2013
Publication Date
January 1, 1983
Subject Category
Metallic Materials
Meeting Information
Meeting: High temperature corrosion; International Conference