Microstructural Investigation of Fe-Ni-Mn-Mo-V-C-N Ferritic Steels by Neutron Diffraction

摘要

The design of alloys, that economize strategic element as chromium requires detailed physical investigations of their structure and phase composition. In the search for new materials in the last two decades a new class of Fe alloys was composed - the so-called nitrogen steels. The contemporary achievements in the casting technology – the use of nitrogen under high preasure above the melt – made possible the production of Fe alloys with nitrogen concentration even above 0.4 wt %. The wide application of investigated alloy system is connected with creation of alloys without presence of strong carbides-forming elements. The microstructure and phase formation of these new materials are insufficiently studied. The aim of this work is to characterize the microstructure and phase composition of two series Fe-alloys casted with and without nitrogen pressure above the melt. The so cast steels appear as experimental ones and they are directed to demonstrate the possibility for nitrogen doping of steels without presence of Chromium in them. The latter is technologically difficult to fulfil at usual conditions. Six samples [with lower nitrogen, N=0.0111 wt %] are cast at normal pressure, and six samples [with higher nitrogen, N=0.2121 wt %] are cast at pressure of 10.106 Pa. The results of Rietveld structure analysis of Time-Of-Flight neutron diffraction data show that studied steels consist of purely ferritic crystal phase (Body Centered Cubic crystal lattice).