Production of niobium vacuum-arc coating on a TiNi-based alloy

Abstract

The aim of this work is to produce a niobium coating by vacuum-arc deposition on a TiNi-based alloy. This method has not been studied in relation to titanium nickelide base alloys and is promising for the production of corrosion and wear resistant coatings for medical and technical applications. The niobium coating is deposited on the semi-finished products (wire and cylindrical specimens) made of titanium nickelide base alloy of composition Ti49.4 Ni50.6 (at pct) and the surface subjected to mechanical grinding. It is stated that the obtained coating with a thickness of about 1 μm possesses drawbacks, such as ‘inherited’ surface profile formed by mechanical grinding of semi-finished products, and the drop phase, which is a typical unavoidable defect for this type of deposition method. At the same time, the surface layer of the alloy with a niobium coating exhibits a significantly higher microhardness (two times more) than the initial alloy. The effect of the revealed defects on the corrosion properties and wear resistance of the alloy requires further study. Bending deformation is used to study the mechanical behavior of the wire in the initial state and after coating deposition; it is stated that the coated wire exhibits superelastic behavior in bending identical to the initial wire. At the same time, deposition of the coating causes the formation of internal stress fields near the wire surface, and the effects of these fields lead to the elimination of non-recoverable deformation in the unloaded wire accumulated in the subsurface layers under loading.