Development of Coating on the Surface of Reduced Activation Ferritic Martensitic Steel (RAFMS) Substrate Using Hot Dip Aluminization and Heat Treatment

Abstract

This study deals with a facile strategy to coat the surface of reduced activation ferritic/martensitic steel (RAFMS) substrate with alumina and aluminide layer. The coating on the surface of the substrate was obtained by using hot dip aluminization technique followed by heat treatment. The thickness, phases, and composition of the coating were analyzed using optical microscopy, XRD, and scanning electron microscopy–EDS studies. Optical microscopy images of the dipped sample revealed the presence of two distinguished layers: an outer thick layer (thickness about 32 µm) and an inner thin layer (thickness about 18 µm). Similarly, optical microscopy images of heat-treated samples indicated the presence of two layers but with increased thickness: outer layer (thickness about 120 µm) and inner layer (thickness about 80 µm). The XRD pattern of dipped sample revealed the presence of Al and Si on the surface of the coating while that of heat-treated sample indicated the presence of Fe₂Al₅, α-Al₂O₃, and θ-Al₂O₃. Scanning electron microscopy–EDS studies revealed the presence of three distinct layers in dipped samples: outer layer consisting of Al and Si having thickness 33 µm, middle finger-like layer having thickness 12 µm and inner layer having thickness of 6 µm. Likewise, for heat-treated sample, three layers were observed but with increased thickness.