Vol.:(0123456789) 1 3 Metallography, Microstructure, and Analysis https://doi.org/10.1007/s13632-018-0509-3 Development of Coating on the Surface of Reduced Activation Ferritic Martensitic Steel (RAFMS) Substrate Using Hot Dip Aluminization and Heat Treatment Japinder Kaur 1  · Kulwant Singh 2  · Bhaskar Paul 3  · M. R. Gonal 4 Received: 15 May 2018 / Revised: 12 September 2018 / Accepted: 18 November 2018 © Springer Science+Business Media, LLC, part of Springer Nature and ASM International 2018 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 Fe 2 Al 5 , α-Al 2 O 3 , and θ-Al 2 O 3 . 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 fnger-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. Keywords Aluminum · Heat treatment · Steel Introduction For Indian test blanket module (TBM), reduced activation ferritic/martensitic steel (RAFMS) is being used as structural material. Surface of RAFMS needs to be protected against corrosion from fowing liquid breeder at 325–480 °C. Per- meation of tritium from Pb-17Li into steel also needs to be prevented. Apart from these issues, electrical insulation for reduction of drag by magnetohydrodynamic efect produced due to the fowing Pb-17Li in conducting channels needs to be considered [1]. In this context, Al-based protective coatings on the surface of RAFMS are gaining immense importance and are considered to be a suitable candidate to mitigate the above-mentioned issues [2, 3]. The present study deals with the coating of RAFMS sub- strate with alumina and aluminide layer by using hot dip aluminization technique followed by heat treatment. Out of various available techniques, hot dip aluminization tech- nique is considered to be a facile and relatively economical method for the coating of substrate [4]. In this technique, the substrate to be coated is treated in an aluminum molten bath. This technique is gaining importance among the researchers because this technique is suitable for the coatings of com- plex geometries. An important parameter which determines the perfor- mance of coating on the substrate for TBM is its thickness. For displaying good results, coatings of less thickness are desirable. For this, a small amount of Si is added to the Al * Japinder Kaur jap.chawla@gmail.com; japinder.kaur@gnkhalsa.edu.in Kulwant Singh singhkw@barc.gov.in 1 Department of Chemistry, G. N. Khalsa College, Matunga, Mumbai 400019, India 2 MSD, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India 3 MP & CED, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India 4 G & AMD, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India