Enhanced Creep Resistance of an Ultrafine‐Grained Ti–6Al–4V Alloy with Modified Surface by Ion Implantation and (Ti + V)N Coating

Abstract

This research examines the creep behavior of an ultrafine‐grained (UFG) Ti−6Al−4V alloy processed by equal‐channel angular pressing followed by extrusion. It is shown that modifying the surface of the UFG alloy with nitrogen ions and then applying of a coating of (Ti + V)N inhibits the softening of the UFG alloy at temperatures up to 700 K due to a barrier effect in which the coating hinders the release of dislocations onto the surface. The differences in the mechanisms of crack initiation and failure of UFG samples are also examined both with and without a coating. The prospects of the proposed approach to the improving of titanium alloys are discussed, including the formation of an UFG structure in the bulk of the material and subsequent modification by ion‐plasma methods for the manufacture of highly loaded parts operating at elevated operating temperatures.

Architecture and Increased Adhesive Strength of Vacuum‐Plasma Coating on Ultrafine‐Grained Titanium Alloy

“…Recently, a similar dependence was observed on vacuum-plasma coatings deposited on UFG CP Ti as well as UFG titanium alloy Ti-6Al-4V. [5,6] It is obvious that the influence of the UFG structure on the hardness and adhesive strength of the coating is of common consistency. This effect can be due to the increase in the crystallization rate of the coating material and its vacuum-plasma deposition on the UFG substrate, resulting in the decrease in the grain/crystal size in the coating.…”

“…In addition to the technical regimes of the coating deposition, one of the main factors affecting the quality of the coating may be the structural state of the substrate material. [5,6] The study of the properties of a TiVN vacuum-plasma coating with vanadium layers on the samples of titanium alloy VT8M-1 conducted in this work demonstrated that substrate grain refinement directly influences the adhesive strength as well as physicomechanical properties of the coating.…”

“…The same coating architecture was made on a sample of a CG alloy as well. [5] Figure 2c shows the diagram of changes of elemental composition on the coating thickness obtained using local X-ray spectral analysis in SEM. The obtained data confirm the coating architecture acquired during deposition.…”

“…At the same time, there are currently only a few studies on the properties of vacuum-plasma coatings deposited on the surface of UFG metals and alloys, and it is of particular interest to investigate this problem for the industrial titanium alloy VT8M-1 (Ti-5.7Al-3.8 Mo-1.2Zr-1.3Sn) applied in aircraft engine manufacturing. [4][5][6][7] The aim of this article is the study of the adhesion strength of TiVN protective coating on the selected alloy after the formation of UFG structure in it, using the famous known SPD technique-rotary swaging (RS). [8,9] The titanium alloy VT8M-1 used in this investigation was provided by VSMPO-AVISMA Corporation (Verkhnaya Salda, Russia) with the following composition wt%: Ti-5.7Al-3.8 Mo-1.2Zr-1.3Sn.…”

“…Then, TiVN vacuum-plasma coating was deposited onto the surface of all samples in accordance with the procedure described in earlier works. [3,5] The choice of its architecture (chemical composition, number of layers, and their thickness) was based on earlier erosion resistance studies, where the coating demonstrated a minimum erosion rate on the samples of Ti-6Al-4V titanium alloy. [3] The erosion rate was found to be reduced by 10 times by application of the TiVN coating.…”