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Optimizing Scale Adhesion on Single Crystal SuperalloysTo improve scale adhesion, single crystal superalloys have been desulfurized to levels below 1 ppmw by hydrogen annealing. A transition to fully adherent behavior has been shown to occur at a sulfur level of about 0.2 ppmw, as demonstrated for PWA 1480, PWA 1484, and Rene N5 single crystal superalloys in 1100-1150 C cyclic oxidation tests up to 2000 h. Small additions of yttrium (15 ppmw) also have been effective in producing adhesion for sulfur contents of about 5 ppmw. Thus the critical Y/S ratio required for adhesion was on the order of 3-to-1 by weight (1-to-1 atomic), in agreement with values estimated from solubility products for yttrium sulfides. While hydrogen annealing greatly improved an undoped alloy, yielding <= 0.01 ppmw S, it also produced benefits for Y-doped alloys without measurably reducing the sulfur content.
Document ID
20000120450
Acquisition Source
Glenn Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Smialek, James L. (NASA Glenn Research Center Cleveland, OH United States)
Pint, Bruce A. (Oak Ridge National Lab. TN United States)
Date Acquired
September 7, 2013
Publication Date
August 1, 2000
Subject Category
Metals And Metallic Materials
Report/Patent Number
NAS 1.15:210362
NASA/TM-2000-210362
E-12411
Meeting Information
Meeting: High Temperature Corrosion and Protection of Materials
Location: Les Embiez
Country: France
Start Date: May 22, 2000
End Date: May 26, 2000
Sponsors: European Federation of Corrosion
Funding Number(s)
PROJECT: RTOP 523-31-13
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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