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U* 1. There was no corrosion or erosion of the graphite by the flowing salt. 2. There was very little permeation of the graphite by the salt, and the permeation that occurred was uniform throughout the graphite rods. 3 . The various INOR-8 loop components exposed to the salt were not carburized. 4 . The INOR-8 components exposed to the salt and graphite were negligibly attacked. 5. With the possible exception of oxygen contamination, the salt appeared to have undergone no chemical changes as a result of exposure to the graphite test specimens. Oxidation Resistance of INOR-8 The oxidation resistance of nickel-molybdenum alloys depends on the service temperature, the temperature cycle, the molybdenum content, and the chromium content. The oxidation rate of the binary nickel-molybdenum alloy passes through a maxim for the alloy containing 15$ Mo, and the scale formed by the oxidation is NiMoO4 and NiO. Upon thermal cycling from above 1400째F to below 660"F, the NiMoO4 undergoes a phase transformation which causes the protective scale on the oxidized metal to spall. Subsequent temperature cycles then result in an accelerated oxidation rate. Similarly, the oxidation rate of nickel-molybdenum alloys containing chromium passes through a maximum for alloys containing between 2 and 646 Cr. Alloys containing more than 6$ Cr are insensitive to thermal cycling and to the molybdenum content because the oxide scale is predominantly stable CrzO3. An abrupt decrease (by a factor of about 40) in the oxidation rate at 1800째F is observed; then the chromium content is increased from 5.9% to 6.246. The oxidation resistance of INOR-8 is excellent, and continuous operation at temperatures up to 1800째F is feasible. Intermittent use at temperatures as high as 1900'F could be tolerated. For temperatures up to 1200"F, the oxidation rate is not measurable; it is essentially zero after 1000 hr of exposure in static air, as well as in nitrogen containing small quantities of air (the MSRE cell environment). It is estimated that oxidation of 0.001 to 0.002 in. would occur in 100,000 hr of operation at 1200째F. The effect of temperature on the oxidation rate of the alloy is shown in Fig. 8. Mechanical Properties of INOR-8 Mechanical properties tests were performed on eight commercial-size heats of INOR-8. Tests were conducted at ORNL,~ the Haynes Stellite Company,6 the Battelle Memorial Institute,7 and the University of Alabama.8 Results indicated that the strength of INOR-8 compares favorably with austenitic stainless steels.

i

ORNL-3708  

http://www.energyfromthorium.com/pdf/ORNL-3708.pdf

ORNL-3708  

http://www.energyfromthorium.com/pdf/ORNL-3708.pdf

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