Abstract
The results of a study of structure, phase, and chemical compositions of nanostructured (Ti,Zr)N coatings formed by vacuum arc deposition on Ti0.16Pd (wt.%) alloy substrates are reported. The coating composition was varied depending on the quasi-binary system δ—TiN—δ—ZrN. The coatings were formed in two modes: without (mode 1) and with (mode 2) rotation of the substrates in a plasma flow. It was shown that irrespective of the deposition regime, the coatings have a single-phase nanograined (grain size ≤ 20 nm) structure of δ-nitrides TiN, (Ti,Zr)N, and ZrN. It is found out that the coatings deposited in accordance with modes 1 and 2 significantly differ in their microstructure. It is demonstrated that in the case of electrolytic hydrogenation in a physiological saline solution (0.9% NaCl), the barrier properties of the coatings deposited via mode 2 are substantially better than those deposited via mode 1 (irrespective of the chemical coating compositions). In the coatings with a regular columnar structure (mode 1), there is a high concentration of hydrogen homogeneously distributed over the coating thickness. In the coatings formed via mode 2 (without columnar microstructure), a high concentration of hydrogen was observed in the subsurface area only. It is found out that there is no hydrogen diffusion into the substrate of these coating both immediately after hydrogenation and after storing for 430 h at room temperature. It was shown that the highest barrier properties were exhibited by the (Ti,Zr)N coatings with the least correlation of spatial distribution of nanograins and Zr/Ti ≤ 1. The hydrogen absorption in the coating based on zirconium nitride increases by a factor of 2.
Highlights
High corrosion resistance, biocompatibility, and high specific strength ensure titanium and its alloys in different engineering applications and as materials for medicine
The coatings with different Zr/Ti ratios, which were deposited via mode 2, had qualitatively similar microstructures
Similar single-phase nanostructure coatings with a chemical composition close to the quasi-binary titanium nitride (TiN)—ZrN system have been formed on the Ti0.16Pd alloy substrates with microcrystalline and SMC structures by the method of vacuum arc deposition from separated plasma flows
Summary
Biocompatibility, and high specific strength ensure titanium and its alloys in different engineering applications and as materials for medicine. The formation of SMC and ultrafinegrained (UFG) structures is a promising trend reducing the tendency of titanium alloys towards developing so-called hydrogen embrittlement in the practical use of these materials. Titanium-based alloys (including Ti0.2Pd) in prolonged contact with hydrogencontaining media can absorb many hydrogen atoms [9,10,11,12]. This gives rise to the formation of hydride phases, a decrease in plasticity, the tendency to cracking and fracture. In the alloys with microcrystalline, SMC, and UFG structures, an increase in the grain-boundary density (the effective centers of trapping of diffusing hydrogen atoms) results in the formation of microcrystalline or nanosized globular hybrid phases, which do not effectively concentrate the stresses initiating cracking and fracture
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
