Surface hardening of TiZrNbHfTa high entropy alloy via oxidation. (June 2023)

• Record Type: Journal Article
• Authors: Dickes, Daniel; Öztürk, Beyza; Baier, Felix; Berger, Pascal; George, Easo P.; Völkl, Rainer; Galetz, Mathias C.; Glatzel, Uwe
• Is Part Of: Corrosion science. Volume 217(2023)
• Publication Date: 2023-06
• Subjects: Alloy -- High temperature corrosion -- Oxidation -- Internal oxidation -- Kinetic parameters -- Hardening; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2023.111159
• Languages: English
• ISSNs: 0010-938X

Abstract

Abstract: We investigate the oxidation of TiZrNbHfTa high entropy alloy between 550 °C and 650 °C as a surface hardening method. Coarse-grained specimens with grain boundaries perpendicular to the surface exhibit catastrophic oxidation, while ultrafine-grained, cold-rolled specimens show a continuous mass gain and the formation of an adherent, µm-sized, vitreous oxide layer. Underneath, TiZrNbHfTa decomposes into a bcc- and an hcp-phase, while selective internal oxidation of hafnium and zirconium occurs upon oxygen inward diffusion. Oxygen concentration- and microhardness-depth profiles confirm an increase in oxygen concentration and hardness at the surface, raising the initial hardness by four times to 1522 ± 64 HV0.5. Graphical Abstract: ga1 Highlights: Microstructure has a significant impact on the oxidation behavior of TiZrNbHfTa. A coarse-grained microstructure causes catastrophic oxidation. An adherent oxide layer only forms on ultafine-grained, cold-rolled specimens. Oxidation of cold-rolled TiZrNbHfTa increased the surface hardness by four times.