Interfacial phenomena between alumina substrate and nickel containing low-alloy steel

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A comprehensive description of the phenomena at the low-alloy Fe-C-O-Ni steel/corundum interface at elevated temperatures up to 1600 °C was performed using the sessile drop method, Differential Thermal Analysis (DTA), 3D Differential Scanning Calorimetry (3D DSC) as well as several supporting methods, namely Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD) analyses and Scanning Electron Microscopy (SEM). Steel samples with different carbon (0.04–1.56 wt%) and nickel (1.08–4.48 wt%) contents were selected to assess the effect of temperature and chemical composition on the related quantities, namely density, surface and interfacial tension, wetting angles, and the work of adhesion. While increased nickel content caused a decrease in wetting angle, and surface and interfacial tension values, the increased carbon content had the opposite effect. Two distinctly different modes of high-temperature interaction at the phase interface were also described. Little interaction was observed between the steel with lower carbon content (<0.1 wt%) and the corundum substrate. On the contrary, a more substantial interaction occurred in steel with higher carbon content and thus lower liquidus temperature. There was significant disruption of the corundum substrate at the surface and in depth up to 140 µm. The original corundum structure was replaced by new structural phases, particularly hibonite, grossite and gehlenite. In addition, when a higher chromium content was present in the steel, chromium-doped corundum was formed.