Iron-Aluminide-Alumina Coating on Reduced Activation Ferritic Martensitic Steel for Nuclear Fusion Reactor Applications
摘要
Reduced Activation Ferritic Martensitic Steel (RAFMS) is a promising structural material for fusion reactors. However, enhancing its performance through effective coatings is crucial. This study investigates Iron-Aluminide-Alumina coatings on RAFMS, applied via hot-dip aluminizing in an Al-10 wt.% Si bath at 750 °C, followed by heat treatment at 950 –1150 °C for 23 –180 minutes. The coatings were characterized using optical microscopy, SEM, EDX, and XRD. Mechanical properties were evaluated through Knoop microhardness and scratch tests. A uniform coating of approximately 120 µm thickness was achieved after 3 minutes of dipping, followed by heat treatment at 950 °C for 45 minutes. XRD analysis revealed the presence of Al and Si phases on the coated surface. The coatings exhibited a two-layer structure, with inward diffusion of Al and Si and outward diffusion of Fe and Cr. Longer heat treatment durations led to increased Fe concentration and a gradual elemental distribution. Porous bands were observed in coatings treated above 1000 °C. Scratch tests at 5N load indicated a tough outer layer, while cracks in the inner layer were observed in coatings heat-treated at 950 °C for shorter durations but disappeared after 180 min. Hardness ranged from 700 –1200 HK, significantly higher than the substrate (<300 HK). Optimal coatings, heat-treated at 950 °C and 1000 °C for 180 min, were crack-free, tough, and rich in α-Al2O3 and θ-Al2O3 phases, making them suitable for fusion applications.
Graphical Abstract