ASPECTS CONCERNING THE CRYSTAL LATTICE BEHAVIOR OF AUSTENITIC STEEL AT LOW TEMPERATURE
Abstract
Two austenitic stainless steels for investigation under cryogenic condition were considered. Both X8CrNi18-12 and X12CrNi25-21 were investigated by X-ray diffraction at several cryogenic temperatures of 298 K, 223 K, 173 K, and 123 K. The crystal parameter and thermal linear expansion coefficient were calculated from the X-ray diffraction pattern. The major observation was the increasing of diffraction angles as temperature decreases. The X8CrNi18-12 crystal parameter presents a significant decreasing related to the same condition applied to X12CrNi25-21. We observe the same tendency for thermal linear expansion coefficient variation which means that X8CrNi18-12 becomes harder and more brittle than X12CrNi25-21 in the same cryogenic condition. Finally the X8CrNi18-12 proves to be useful for cryogenic applications which need high hardness instead of a good toughness and X12CrNi25-21 prove to be useful for cryogenic applications which need a better toughness.
Key words: X-ray diffraction, austenitic stainless steels, elementary cellFull Text:
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