Correlation between Microstructural Change and Irradiation Hardening Behavior of He-Irradiated V–Cr–Ti Alloys with Low Ti Addition

V–4Cr–xTi (x = 0 to 4) alloys were used to investigate the additional effect of Cr, Ti and interstitial impurities on the microstructural evolution in He-irradiated V–Cr–Ti alloys to minimize radioactivity after fusion neutron irradiation. Transmission electron microscopy and atom probe tomography were carried out to the He-irradiated specimens at 500 °C with 0.5 dpa at peak damage. A flash electro-polishing method for the FIB-extracted specimen was established for the ion-irradiated vanadium alloys. The microstructural evolution of the irradiation-induced titanium-oxycarbonitride, Ti(CON) precipitates was observed and was influenced by the effect of Ti addition on the Ti(CON) precipitation. Apparent Ti(CON) precipitates formed in V-4Cr-xTi with 2% addition of Ti. In the V-4Cr-1Ti alloy, a high density Ti enriched cluster was formed. The origin of the irradiation hardening increase resulted from the size distribution of Ti(CON) precipitation from the dispersed barrier-hardening theory.

Microstructure and electrochemical properties of the vanadium alloys after low-temperature nitrogen plasma treatment

Purpose: The proposed research aims to determine the expediency of surface treatment of vanadium alloys of V-Cr and V-Ti systems due to irradiation of their surfaces with low- temperature nitrogen plasma using plasma torch NO-01. Design/methodology/approach: The investigation of microstructure and X-ray fluorescence analysis (XRF) of the samples were performed using an electron microscope TESCAN Vega3. The microhardness (Vickers hardness) of the samples was measured before and after surface treatment. The study of corrosive properties of the surface layers was performed by an electrochemical impedance spectroscopy (EIS) method. Corrosion damages were identified using impedance dependences. Findings: The microstructure of the surface layers of the V-8Ti, V-15Cr, and V-35Cr alloys in the initial state and after plasma treatment have been investigated. The chemical composition of the surface layers is determined and comparative measurements of the microhardness of these alloys are carried out. Corrosion-electrochemical properties (corrosion potentials, electrochemical impedance spectroscopy and constructed potential-dynamic polarization curves) of investigated alloys after treatment with nitrogen plasma are evaluated. Research limitations/implications: The results obtained using laboratory samples should be checked at the conditions of power equipment operation. Practical implications: This treatment has advantages over other methods of surface engineering since it provides strong surface plastic deformation and the possibility of formation of secondary phases resulting in increases in surface hardness and corrosion resistance. Originality/value: Vanadium alloys have significant advantages over other structural materials due to their high thermal conductivity and swelling resistance, high strength and plasticity up to temperatures of 700-800°C, and good weldability.