Crystallographic structure of vanadium carbide precipitates in a model Fe-C-V steel

Abstract

The crystallographic structure of vanadium carbide precipitates in iron is investigated using High Resolution Transmission Electron Microscopy (HRTEM) and conventional Selected Area Diffraction (SAD) analysis. After a two-step precipitation treatment (10 hours at 700°C and 10 days at 800°C) and different annealing treatments (from 870 to 920°C) performed on an ultra-pure Fe–V–C model alloy, carbides exhibit unambiguously the ordered monoclinic form V6C5. The often reported V4C3 structure, that refers to the pioneering work by Baker and Nutting is not encountered in the present investigation. Reasons for this contradiction are discussed, and the conclusion is drawn that no literature data are available to unambiguously support the existence of precipitates with the V4C3 structure.