3439.    TRILLAT, J. J., AND OKETANI, S.  [Electron-Diffraction Study of the Cementation of Iron.  I.  Action of Pure Carbon Monoxide.]  Compt. rend., vol. 230, 1950, pp. 2,203-2,205; Chem. Abs., vol. 44, 1950, p. 10,631.

        Extremely thin polycrystalline films were prepared by vaporizing from pure Fe or mild steel onto the surface of freshly cleaved rock salt; the salt was then dissolved in H2O and the metallic film collected on a Ni grill.  This was submitted to cementation in the presence of pure CO and then examined by electron diffraction.  After cementation at 540, orthohombic crystals of cementite are present.  Below 500 none is formed.  At 540, if the preparations are not exposed constantly to fresh CO2, decomposition takes place forming Fe3O4.  As the temperature is raised, graphite is deposited on the surface, and above 820 the diagrams of Fe and Fe3C are masked.