Influence of nitrogen-bearing gaseous environment on physical and mechanical properties of niobium

Mechanical and physical properties of niobium are studied as affected by gaseous atmospheres (N2+5% O2 and nitrogen-hydrogen mixture) at different holding time within the temperature range of 300-900 deg C. It is found that the ultimate strength of the metal grows during interaction of the nitrohydrogeneous mixture with niobium specimens an increase of their holding fime in gaseous atmospheres as against specimens tested in vacuum at the same temperatures. But in the N2+5% O2 medium the mechanical strength falls. Microhardness of niobium specimens tested in the nitrohydrogeneous mixture at the temperature of 900 deg C increases. The X-ray diffraction analysis showed existence of NbN and Nb2N nitrides after treatment in the nitrohydrogeneous mixture; NbO and NbO2 are additionally found in niobium treated in the N2+5% O2 medium