Surface modifications and the mechanical properties of carbon steels implanted with nitrogen

Abstract

Discusses the relationships between the surface composition and the mechanical properties of carbon steels implanted with nitrogen. Conversion electron and X-ray Mossbauer spectroscopy (CEMS and CXMS) were used to investigate the surface modifications of the implanted samples. Thermal annealing was performed in high vacuum, at temperatures between 250 and 500 degrees C, in order to simulate the temperature increase in real tribological processes. It is shown that the improved performance of nitrogen-implanted carbon steels against wear and fatigue is mainly due to the action of finely dispersed iron carbonitrides ( theta - and epsilon -Fe3(C,N)). It is shown also that the persistence of the protective action at greater depths is associated with the in-diffusion of nitrogen released by thermal decomposition of the compounds formed at the surface.