Characterization of oxide scales to evaluate high temperature oxidation behavior of Ti(C,N)-based cermets in static air

• Published in: Journal of alloys and compounds 2010-09, Vol.506 (1), p.461-467
• Main Authors: Yang, Qingqing, Xiong, Weihao, Li, Shiqi, Dai, Hongxia, Li, Jun
• Format: Article
• Language: English
• Subjects: Binders; Cermets; Chromium; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; High temperature; Materials science; Nickel; Other materials; Oxidation; Oxidation behavior; Oxide scales; Oxides; Physics; Scale (corrosion); Specific materials; Ti(C,N)-based cermets; Titanium dioxide; Transition layers
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2010.07.031

▶ Oxide scales formed consisted of NiO outerlayer, NiTiO 3 interlayer and TiO 2-based innerlayer. ▶ Transition layers formed consisted of Ti-, Ni- and Mo-based oxides. ▶ Oxidation process was mainly controlled by O inward thermodynamic activity. ▶ Cermet with Ni–20Cr binder exhibited better oxidation resistance, due to the richness of Cr in binder and rim phases. ▶ Cr was completely and incompletely oxidized to form Cr 0.17Mo 0.83O 2 and Cr-rich Ti-based oxides, respectively, thus decreasing O inward thermodynamic activity. Two Ti(C,N)-based cermets with Ni and Ni–20Cr metallic binder were oxidized at 800 °C and 1000 °C for up to 100 h in static air, and the oxide scales and the transition layers formed on both the cermets were characterized to evaluate their high temperature oxidation behavior in static air using XRD, SEM and EDS. The oxide scales formed on both the cermets at 800 °C and 1000 °C were not dense, and were multi-layered, consisting of NiO outerlayer, NiTiO 3 interlayer and TiO 2-based innerlayer. The transition layers were present between the oxide scales and the substrates with increasing oxidation time, which consisted of Ti-based, Ni-based and Mo-based oxides. Oxidation process of both the cermets was mainly controlled by O inward thermodynamic activity, and oxidation at 1000 °C was faster than that at 800 °C. However, cermet with Ni–20Cr metallic binder was oxidized slower than cermet with Ni metallic binder, due to the richness of Cr in Ni-based binder phase and the rim phase of Ti(C,N) ceramic grains. Cr was completely oxidized to form Cr 0.17Mo 0.83O 2, and was incompletely oxidized to Cr-rich Ti-based oxides, leading to the decrease of O inward thermodynamic activity.