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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 39204 (07)
- University: Sharif University of Technology
- Department: Material Science and Engineering
- Advisor(s): Kokabi, Amir Hossein
- Abstract:
- IC221M is a cast Ni3AI-based intermetallic alloy which chemical composition bases on Ni- 8Al-8Cr-1.5Mo-1Zr-O.OIB %wt. Because of high strength, good high temperature oxidation, carburization and creep resistance as mechanical and physical properties, IC221M has got good attention in aeronautical, military and steel production industries nowadays. The best service temperature range is 600-800°C and melting starts at II 70°C. Since 1993 according to broad range of researches and applications, ASTM standardized it at Al002-99 and from that time researchers try to replace steel with IC221M. %80 volume of microstructure in this alloy consisted of brittle y' and remain are y and low melting point eutectic Ni5Zr phase. IC221M is the only nickel base aluminide alloy which is weldable.Welding of!C221M is very difficult due to the solidification cracking. Weldability of this alloy very susceptible to chemical composition and at the certain welding parameters of current density and welding speed, sound welds will be produced. According to the studies, the solution is increasing the Zr content in the composition. Zirconium with increasing the amount of Ni5Zr the final solidifying phase, back fill the emptied spaces due to solidification shrinkage which is the main cause of cracking. For that reason, cast IC221 W based on Ni-8Al-8Cr-1.5Mo-3Zr-O.OIB %wt produced. IC221M and IC221Win three type samples and different parameters welded with autogenous GTAW to access optimum range of parameters and weld metal composition. Results showed, weldmetal consists of 2.5-3 o/owt of Zr will be sound. In the second section of this project, Weldability of dissimilar joints ofiC221M and 301 stainless steel discussed and the optimum parameters extracted. Optical and scanning electron microscopy (SEM) utilized with X-ray energy dispersive spectroscopy (EDX) techniques used to study the microstructure and different phases composition. X-ray diffraction used to explore phases and probability of new phases formation in weldrnetals. hardness, micro hardness, tensioJ;J. and impact tests as mechanical testing utilized to compare weldments with base alloys. Finally, fracture behavior of tension and impact specimens investigated with SEM. There is a expectation that the results will be useful to suitable filler metals for IC221M welding.
- Keywords:
- Microstructure ; Mechanical Properties ; Intermetallic Compounds ; Gas Tungsten Arc Welding (GTAW) ; Nicle Aluminide Base Alloy ; Dissimilar Joint
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