A Coupled Thermal, Fluid Flow, and Solidification Model for the Processing of Single-Crystal Alloy CMSX-4 Through Scanni
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rder to improve the efficiency of gas turbine engines through higher operating temperatures, investment cast equiaxed turbine component parts are now increasingly being replaced by components that have either directionally solidified (DS) or single-crystal (SX) columnar microstructure. During operation, these SX
RANADIP ACHARYA, Ph.D. Candidate, is with the George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Dr., Atlanta, GA 30332-0405. ROHAN BANSAL, formerly a Graduate Student with the George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, is now Ph.D. with the Chart Industries, Buffalo, NY. JUSTIN J. GAMBONE, formerly a Graduate Student with the George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, is now M.S. with GE Global Research, Niskayuna, NY. SUMAN DAS, Professor and Morris M. Bryan, Jr. Chair, is with the George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, and also with the School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Dr. NW, Atlanta, GA 30332-0405. Contact e-mail: [email protected] Manuscript submitted January 20, 2014. Article published online July 15, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
components undergo damage and wear which limits their lifetime, necessitating the replacement of numerous components within the engines. The result is high maintenance, repair, and overhaul costs. For instance, within each engine containing several hundred turbine blades, the total cost to replace every damaged airfoil can reach hundreds of thousands to millions of dollars. Therefore, a process that can restore SX components back to parent metallurgy and microstructure at the damage location and allow hot-section components to be reused rather than scrapped is of great interest. Hot-section turbine component repairs were first attempted using processes such as tungsten inert gas welding and laser melting using a defocused beam.[1,2] These processes either could not create SX deposits, could not be applied to complex geometries, or suffered from crack formation.[3] Laser engineered net shaping, laser cladding, and epitaxial laser metal forming (ELMF) have more recently attempted to restore SX airfoils to working condition.[4–6] However, crack formation, CET, oriented-to-misoriented transition (OMT), and stray grain formation hinder the applicability of all of the above processes in highreliability repair of single-crystal hot-section turbine components.[3,7–10] VOLUME 45B, DECEMBER 2014—2247
Scanning laser epitaxy (SLE) is a laser-based additive manufacturing process for the creation of structures in equiaxed, DS, and SX nickel superalloys through the layerwise selective melting and re-solidification of superalloy powders placed on superalloy substrates. In SLE, a tightly focused laser beam is guided by high-speed galvanometer scanners allowing for tight control over the amount of energy being applied to the top of the preplaced powde
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