A New Iron Boro-carbide

Abstract

DURING a current investigation of the phase relations in the iron–carbon–boron system, X-ray diffraction has revealed the existence of a new boro-carbide which appears to have the structure of the complex cubic carbide reported by Westgren¹ in the chromium–carbon system. He showed that the idealized unit cell contains 92 Cr atoms and 24 C atoms, thus corresponding to the composition Cr₂₃C₆; moreover, about 25 per cent of the chromium may be replaced by iron in this carbide. Westgren also reported carbides of similar structure in the iron–molybdenum–carbon and iron–tungsten–carbon systems, in particular in high-speed steels; these carbides, which have been designated ‘kappa’ by Goldschmidt², correspond, at least approximately, to the compositions Fe₂₁Mo₂C₆ and Fe₂₁W₂C₆. Comparison of the diffraction data for the present boro-carbide with that for the complex cubic chromium carbide as described by Goldschmidt³ is presented in Table 1. The lattice parameter of the boro-carbide is found to be 10.62 + or 0.02 A.