Abstract
A diffusion-barrier coating layer (DBC) was formed on a Ni–22Cr–19Fe–9Mo alloy by Al-pack cementation at 1000°C followed by heat treatment at 1100°C. The thermal cyclic oxidation behavior of the DBC system was then investigated. The thermal cycle oxidation tests were conducted at 1100°C in air for 45 min, each followed by 15 min at room temperature. Electron probe micro-analysis (EPMA) was performed to determine the microstructure and concentration profile of each element between the substrate and the coating layer.
The DBC system showed good thermal cycle oxidation property. The layer structure between the substrate and the coating layer after thermal oxidation cycling is discussed with respect to the composition paths plotted in the Ni–Cr–Fe and Ni–Cr–Al phase diagrams. The coating layer structure after 100 cycles of 45 min at 1100°C consisted of the γ- and α-phases of the Ni–Cr–Fe system and the β-phase of the Ni–Cr–Al system. The coating layer structure after 400 cycles of 45 min at 1100°C consisted of the γ-phase of the Ni–Cr–Fe system and the β-phase of the Ni–Cr–Al system. In contrast, the coating layer structure after 900 cycles of 45 min at 1100°C consisted of the γ-phase of the Ni–Cr–Fe system.
This Paper was Originally Published in J. Japan Inst. Met. Mater. 83 (2019) 372–377.
Fig. 3 Mass gain as a function of the square root of the cycle number for the uncoated and coated specimens during thermal oxidation cycling at 1100°C.
Fullsize Image
