IJIRST –International Journal for Innovative Research in Science & Technology| Volume 4 | Issue 9 | February 2018 ISSN (online): 2349-6010 All rights reserved by www.ijirst.org 107 Enhancement of Insulation Properties of RAFM Steel Surface by Development of Thin Film Coating of Aluminium Oxide by Laser Technique S. P. Chakraborty N. K. Chakraborty Scientific Officer Scientific Assistant Materials Group/ Bhabha Atomic Research Centre Trombay, Mumbai-400085 Materials Group/ Bhabha Atomic Research Centre Trombay, Mumbai-400085 Madan Gopal Krishnan Associate Director Materials Group/ Bhabha Atomic Research Centre Trombay, Mumbai-400085 Abstract Reduced activation Ferritic/Martensitic steel (RAFMS) is a potential candidate material for structural applications specially as coolant channels in the Indian Test Blanket Module System (TBM) for International Thermonuclear Experimental Reactor (ITER). In order to prevent any pressure drop effect during the flow of metallic coolant of Pb-Li liquid through the RAFMS cooling channels due to magneto-hydrodynamic effect (MHD), surface coating with high electrical insulating properties is required prior to use. Hence, in the present study, investigations were carried out to develop coating of alumina (Al2O3) on RAFM steel substrate by pulse laser deposition (PLD) technique as alumina has unique properties of high electrical insulation properties. Moreover, by laser technique, it was possible to obtain defect free surface with impervious layer of thin film coating of alumina which is responsible to render high electrical insulation property. Laser pulse transformed the meta-stable Al-O (γ) phase present in the alumina target into thermodynamically stable Al-O (α) phase in the coating. Maximum coating thickness of 2 μm was achieved having uniform and defect free surface. High electrical insulation property in terms of electrical resistivity was achieved (electrical resistivity value: 2.14 x 10 6 ohm.cm). The alumina coating further showed very high hardness of value of 400 VHN and high adhesive strength of the order of 15 MPa. Keywords: Laser, Deposition, Alumina, Coating, RAFMS, Characterization _______________________________________________________________________________________________________ I. INTRODUCTION The surface engineering plays an important role for the enhancement/modification of the surface properties of various engineering components to combat against adverse environment in which the parts are subjected. The choice of a surface material with appropriate thermal, electrical and magnetic properties and having adequate resistance to wear, corrosion and degradation is crucial for its functionality. Continuous efforts to enhance the surface properties of various engineering components has resulted in the development of various surface coating techniques such as chemical Vapour Deposition (CVD), Magnetron Sputtering (MS), Pulsed Laser Deposition (PLD) processes etc.. Laser surface modification is an emerging field, wherein lasers are used for imparting superior surface properties on engineering components. In this regard, PLD based excimer laser method is extensively used in microelectronics, biomedical and surface engineering applications to produce functional protective coating films. PLD is a physical vapor deposition (PVD) technique in which a short laser pulse (10 to 30 ns) is focused onto a solid target. The laser rapidly raises the surface temperature of a small portion of the target beyond the vaporization temperature. A plume of evaporated material is ejected from the target is collected and transferred on a nearby substrate to depose high quality coating onto the substrate [1-3]. Alumina (Al2O3) on account of its excellent chemical, dielectric, optical, tribological and biomedical properties, alumina films are widely used in biomedical and tribological applications due to higher chemical inertness, excellent wear resistance; hardness and better surface finish. Moreover, aluminum oxide has an excellent chemical compatibility, high electrical resistivity and capability to provide impervious layer of coating against any leakage. Therefore, it has attracted significant attention for a wide range of applications including oxidation and hot corrosion resistance, wear resistance, heat and thermal shock resistance and electrical insulation [4]. Reduced activation Ferritic / Martensitic steel is a potential candidate material for structural applications for Indian Test Blanket Module system for International Thermonuclear Experimental Reactor (ITER) system. However, high electrically insulating coating on RAFM steel is an essential prerequisite prior to use as cooling channels in the blanket system to prevent any pressure