Pulsed-Current Electrochemical Codeposition and Heat Treatment of Ti-Dispersed Ni-Matrix Layers
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ELECTROCHEMICAL codeposition is a technique for a particle-dispersed metal-matrix composite coating by electroplating a cathode in an electrolyte solution in which particles are stably suspended.[1,2] The mechanical and chemical properties of the composite coatings may be enhanced by the types of dispersed particles. Hard and inert particles, e.g., Al2O3,[3–6] TiO2,[7] SiC,[8–10] and WC,[11,12] were codeposited with metal-matrix coatings to improve hardness and wear resistance. Electrochemical codeposition has also been employed to produce intermetallic alloy coatings via a two-stage process that includes codeposition of a metallic particle composite coating and a subsequent heat treatment process for alloy homogenization.[13–16] For example, a layer of PATHOMPONG JANETAISONG, formerly Graduate Student with the Department of Materials Engineering, Faculty of Engineering, Kasetsart University, 50 Ngamwongwan Rd., Chatuchak, Bangkok 10900, Thailand, is now Research Assistant with the National Metal and Materials Technology Center (MTEC), Pathum Thani, Thailand. YUTTANANT BOONYONGMANEERAT, Associate Professor, is with the Metallurgy and Materials Science Research Institute, Chulalongkorn University, Soi Chula 12, Phayathai Rd., Pathumwan, Bangkok 10330, Thailand. RATCHATEE TECHAPIESANCHAROENKIJ, Assistant Professor and Director of Materials Innovation Center, is with the Department of Materials Engineering, Faculty of Engineering, Kasetsart University, 50 Ngamwongwan Rd., Chatuchak, Bangkok 10900, Thailand, and also with the Materials Innovation Center, Faculty of Engineering, Kasetsart University, 50 Ngamwongwan Rd., Chatuchak, Bangkok 10900, Thailand. Contact e-mail: [email protected] Manuscript submitted January 23, 2016. Article published online May 23, 2016. 2222—VOLUME 47B, AUGUST 2016
Ni-Ni3Al intermetallic alloy was successfully produced by codepositing an Al-dispersed Ni-matrix composite coating and subsequently annealing the coating under a vacuum at 823 K to 1073 K (550 °C to 800 °C) for 2 hours to form the Ni3Al compound.[14] In comparison with other coating processes, such as hot spray coating, the electrochemical codeposition is a process of interest due to its flexibility and economical advantages.[1] Nickel-Titanium alloy (NiTi), an intermetallic alloy system that exhibits superelasticity and shape memory properties, is one of the alloy systems in which the codeposition could potentially be applied as its alternative processing method.[15–17] Typically, a NiTi film is fabricated on a substrate by the physical vapor deposition (PVD) methods with an ability to fabricate nano-sized film at high-dimensional and composition precision.[18–21] However, the process requires expensive setups and yields low deposition rates with limitation of maximum sizes and shapes.[19–21] For faster production and lower manufacturing costs, NiTi alloys may be alternatively manufactured by a powder metallurgy process;[22–24] yet, the powder process has a limitation of potential minimum size, which is limited to sub-millimeter
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