4 Int. J. Microstructure and Materials Properties, Vol. 8, Nos. 1/2, 2013 Copyright © 2013 Inderscience Enterprises Ltd. Multilayer laser-assisted deposition on single crystal superalloy substrates R. Vilar* and A. Almeida Department of Chemical Engineering and ICEMS, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal Fax: +351-218418120 E-mail: rui.vilar@ist.utl.pt E-mail: amelia.almeida@ist.utl.pt *Corresponding author E. Costa Santos Department of Mechanical Engineering, Kyushu University, Motooka 744, Nishi-ku, Fukuoka-ken 819-0395, Japan Fax: + 81-928023063 E-mail: edson.costasantos@gmail.com Abstract: Laser powder deposition is a promising method for repairing single crystal Ni-based superalloy components used in the hot section of gas turbine engines. In this paper, recent results on multilayer deposits of NiCrAlY and René N4 on (100) single crystal substrates of SRR99- and CMSX-4 Ni-based superalloys are summarised. The deposited material presents a columnar dendritic microstructure consisting of arrays of similarly oriented dendrites forming a mosaic single crystal. Since solidification is epitaxial, the deposits inherit the orientation of the substrate. After aging, the ′-Ni3Al precipitates do not present the cuboid shape required for high-temperature strength owing to chemical segregation within the dendrite arms resulting from solidification solute partition. Heat treatments capable of creating the proper particle microstructures were devised. Keywords: laser powder deposition; laser cladding; single crystal repair; superalloys; turbine blades. Reference to this paper should be made as follows: Vilar, R., Almeida, A. and Santos, E.C. (2013) ‘Multilayer laser-assisted deposition on single crystal superalloy substrates’, Int. J. Microstructure and Materials Properties, Vol. 8, Nos. 1/2, pp.4–16. Biographical notes: Rui Vilar is a Full Professor in the Department of Chemical Engineering of Instituto Superior Tecnico, Technical University of Lisbon, Portugal. He has a degree in Metallurgical Engineer and a PhD in Physical Metallurgy from the University of Paris Sud, Orsay, France. He is the Head of LaserMat – Materials Processing and Design Group of IST and has more than 30 years of experience in research and teaching and has worked