The influence of carbon on nitrogen substitution in iron ε-phases

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. The lower number of electrons contributed to the iron 3d-orbitals by C atoms than by N atoms is considered the cause of the above phenomenon. The variation of other hyperfine parameters with composition is also discussed.