Tantalum coatings formed on titanium by electrospark deposition with computer numerical control in a controlled gas environment

Abstract

Tantalum coatings were obtained on commercially pure titanium by electrospark deposition (ESD) at normal (760 Torr) and reduced (380 Torr) pressure in air or argon atmosphere. A monolayer of ESD tantalum coating with the thickness from 3.6 to 6.5 to 13.2–22.0 μm was applied at the working current of 0.5–2.0 A and constant speed of movement of the tool electrode equal to 60 mm/min along the trajectory, which was set using a complex with computer numerical control (CNC). The width of the deposited tracks in air atmosphere varied from 0.27 to 0.49 to 0.41–0.89 mm and in argon the track width stabilized in the range of 0.73–0.85 mm at an operating current of 1.0–2.0 A. The coatings formed in air were characterized by a high oxygen content from 17.36 to 19.38 to 40.81–47.15 at.% and nitrogen from 2.07 to 2.61 to 3.73–4.17 at.%, an average splat value from 72.6 to 74.4 to 118.1–202.4 μm, and microhardness from 5.4 to 7.7 to 12.1–12.3 GPa. The use of an argon environment allowed limiting the oxygen content in the range of 17.99–41.00 at.%, lowering the nitrogen content to 1.65–2.20 at.%, stabilization of the average splat size in the range of 89.0–121.9 μm, and reduction in the microhardness to 5.3–9.0 GPa.