Effect of deformation with subsequent nitriding on the properties of niobium alloys

Conclusions

• 1. Nitriding leads to the formation of a nitride zone and a zone of internal nitriding on the surface of niobium alloys; the thickness of these zones increases with rising temperature and with increasing saturation time, and it changes extremally in dependence on the preliminary plastic deformation in rolling. The zone of internal nitriding is thickest in specimens subjected to a degree of deformation up to 50%; the thickness of the nitride zone is then minimal. The formation of a more developed sublayer ensures greater hardness at greater depth.

• 2. Nitriding of niobium alloys in the recrystallized state leads to better strength properties and lower ductile properties. Nitriding of niobium alloys in the deformed state leads to a noticeable decrease of strength, apparently because of strong embrittlement. With the degree of deformation increasing to 50%, the strength of niobium alloys after nitriding increases, and when the degree of deformation increases further to 75 and 90%, it decreases.

• 3. Niobium alloys deformed before nitriding to a low degree (up to 50%) have the highest creep limit and the lowest wear resistance.