Accession Number : AD0011700


Title :   CHROMIUM-NITROGEN AND CHROMIUM-OXYGEN EQUILIBRIUM SYSTEMS


Descriptive Note : Interim rept. no. 1, 1 Jul-31 Dec 1952


Corporate Author : RENSSELAER POLYTECHNIC INST TROY NY


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/011700.pdf


Report Date : 31 Dec 1952


Pagination or Media Count : 55


Abstract : Apparatus for the preparation of Cr-O alloys below the dissociation pressure of Cr2O3 was improved to produce a range of compositions in the single phase alpha-Cr region of the constitution diagram. By using a vacuum-fusion method to analyze the alloys for O, the solubility limit of O at 940 deg C was tentatively set at 0.45 to 0.49 wt-%. Experiments with atmospheres of high O content indicated that only Cr2O3 was formed. Attempts to establish the dissociation pressure vs temperature curve for Cr2O3 by bracketing the temperature at various partial pressures were insensitive. The high N-containing alloys obtained with NH3-He atmospheres established the boundary of the Cr2N phase at about 11 wt-% N at 900 deg C, which agreed with the stoichiometric ratio. N-He atmospheres produced low N alloys; data were insufficient to establish a point on the diagram. The dissociation pressures of the CrN and Cr2N phases at 900 deg C appeared to be close to each other. The structure and dimensions of the Cr2N phase were similar to those of hexagonal Cr reported in the literature. Nitriding solid Cr produced a very hard and corrosion-resistant case. Studies of weight changes during nitriding indicated the insensitivity of this method as a means of locating phase boundaries.


Descriptors :   *ALLOYS , RATIOS , TEMPERATURE , BOUNDARIES , LIMITATIONS , PRESSURE , SOLUBILITY , STOICHIOMETRY , PARTIAL PRESSURE , DIAGRAMS , DISSOCIATION , NITRIDING , WEIGHT , CORROSION RESISTANCE , GRAPHS , SOLIDS


Subject Categories : Metallurgy and Metallography


Distribution Statement : APPROVED FOR PUBLIC RELEASE