Structure and phase composition of Nb/Ti system subjected to compression plasma flow impact

The results of structure, phase composition and mechanical properties of titanium alloyed with niobium atoms by means of compression plasma flow (CPF) impact on the “Nb coating (2.5 μm)/Ti substrate” system are presented. The CPF treatment with the pulse duration of 100 μs was carried out at the absorbed energy density of 13 J/cm2 which is sufficient for melting of both niobium coating and some part of titanium substrate. The cross-section analysis by means of scanning electron microscopy revealed the formation of the alloyed layer with the thickness of 14 μm and relatively uniform distribution of Nb along the depth (Nb concentration obtained by means of the EDX analysis was about 17 at.%). Alloying of titanium with Nb atoms resulted in stabilization of a high-temperature β-Ti phase as a β-Ti(Nb) solid solution. In the near surface layer the niobium interacted with impurity atoms (N and C) providing carbonitride (Nb(C,N) and carbide and Nb2C) possible formation. Phase transformation in the surface layer of titanium led to microhardness increase up to 4.7 GPa.