PetroMat

IRON-CHROMIUM ALLOYS PLATES WERE HEATED AT 840 K IN FUSED SALT BATHS WITH HIGH ALKALINE CYANATE CONTENTS. LONG-TERM HEAT TREATMENT UNDER THESE CONDITIONS LED TO THE FORMATION OF A(FE,CR) (C,O,N) PHASE ON THE SURFACE OF THE SPECIMEN. THE CHARACTERISTICS OF THE PHASE WERE INVESTIGATED BY X-RAY DIFFRACTION ANALYSIS, MICROPROBE DETERMINATION AND CHEMICAL ANALYSIS. THE PHASE HAS A CUBIC (NACL TYPE) UNIT CELL WITH A LATTICE PARAMETER INTERMEDIATE BETWEEN THOSE OF CRN AND WUSTITE.AS IN THE CASE OF WUSTITE, THE STRUCTURE IS IRON-DEFICIENT AND BECOMES MUCH MORE SO AS OXYGEN IS ADDED.

Mössbauer spectroscopy of nitrided and carbonitrided iron powders and plates with total interstitial atom contents of between 24 and 33 at% has allowed the variation with composition of the hyperfine magnetic fields of metal atoms with 2 or 3 close interstitial atoms to be determined. Fe atoms with three non-metal nearest neighbours and paramagnetic behaviour have also been detected. Only when the content of non-metal atoms goes beyond 30 at%, do Fe atoms in ε-carbonitrides display higher magnetic fields than in the corresponding ε-nitrides.