MOLYBDENUM-NITROGEN AND MOLYBDENUM-CARBON COMPLEX FORMATION IN STEELS

Abstract
The austenitic phase of four nitrogen containing duplex austenitic-ferritic stainless steels was studied by microhardness measurements and atom probe analysis. The hardness increased with nitrogen content, and atom probe analysis showed that a large fraction of the nitrogen atoms appeared as MoN molecular ions. It is argued that the observation of such molecular ions is due to the presence of Mo-N complexes in the austenite. Few CrN ions were observed, but the existence of Cr-N complexes cannot be ruled out. Comparison with earlier data from the martensitic and ferritic matrices of high speed steels suggest that also in these a complex formation may occur : ions of the type MoC were sometimes observed although to a much lesser extent than MoN in austenite. In the latter case, between 70 and 100% of the least abundant of Mo and N was observed as MoN.