Mechanical properties and corrosion behavior of the nitriding surface layer of Ti-6Al-7Nb using large pulsed electron beam (LPEB)

Abstract

Large pulsed electron beam (LPEB) irradiation was used as a single surface finishing process for Ti-Al-7Nb. Nitrogen plasma gas and cathodic apparatus have been adopted to induce nitriding effect of Ti-6Al-7Nb during the electron beam irradiation. The atomic concentration of nitrogen atoms at the re-solidified layer could be achieved up to ∼18% by LPEB nitriding. Nano-hardness in the re-solidified layer was improved by ∼75% following the irradiation process, as a result of a phase transformation and the formation of TiN. The re-solidified layer induced by the LPEB nitriding, consisted of TiN, TiO2, and TiOxNy, indicated significantly modified corrosion resistance showing a nobler corrosion potential, decreased corrosion current density, and improved charge transfer resistance. The increasing fraction of TiN at the re-solidified layer, induced by LPEB nitriding, was suggested as being responsible for remarkable improvement of mechanical properties and corrosion resistance, embedding uniformly noble and stable characteristics at the top surface. The corrosion-resistant surface layer with superior mechanical properties on Ti-6Al-7Nb has been successfully demonstrated by LPEB nitriding technique.