Titanium nickelide-based alloys: Surface modification with ion beams, plasma flows, and chemical treatment

The effects of the parameters of ion modification of the surface and ion nitriding of TiNi-based alloys on the elemental composition, structural and phase states of the modified layers, and corrosion properties of these alloys have been investigated. It is shown that the most important effects of ion-beam action on the surface of TiNi-based alloys are (1) the saturation of their outer surface layers up to 30 nm thick with oxygen and (2) a change in the elemental composition of the target with the formation of a nickel-free and a following nickel-depleted layer, so that the total thickness of the layer with a low Ni content reaches 60 nm. With the TiNi alloy as an example, we demonstrated the potential of using ion nitriding for obtaining graded alloys with a shape-memory effect that possess a protective hardening nitride layer with a lower (by a factor of about 5) content of nickel at its surface and a multizone structure of the diffusion zone adjacent to the nitride layer.