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dc.contributor.supervisor Ojo, Olanrewaju (Mechanical and Manufacturing Engineering) en_US
dc.contributor.author Osoba, Lawrence
dc.date.accessioned 2012-08-09T22:09:37Z
dc.date.available 2012-08-09T22:09:37Z
dc.date.issued 2012 en_US
dc.date.issued 2012 en_US
dc.identifier.citation L.O. Osoba, R.G. Ding and O.A. Ojo, “Microstructural Analysis of laser weld fusion zone in Haynes 282 superalloy” en_US
dc.identifier.citation L.O. Osoba and O.A. Ojo, “Influence of laser welding heat input on HAZ cracking in newly developed Haynes 282 superalloy” en_US
dc.identifier.uri http://hdl.handle.net/1993/8156
dc.description.abstract Haynes alloy 282 is a new gamma prime (γ’) precipitation strengthened nickel-base superalloy developed for high temperature applications in land-based and aero turbine engines. Joining is a crucial process both during the manufacturing of new components and repair of service-damaged turbine parts. Unfortunately, the new superalloy cracks during laser beam welding (LBW), which is an attractive technique for joining superalloys components due to its low heat input characteristic that preclude the geometrical distortion of welded components. This research is therefore initiated with the goal of studying and developing an effective approach for preventing or minimizing cracking during LBW of the new superalloy Haynes 282. Careful and detailed electron microscopy and spectroscopy study reveal, for the first time, the formation of sub-micron grain boundary M5B3 particles, in the material. Microstructural study of welded specimens coupled with Gleeble thermo-mechanical physical simulations shows that the primary cause of weld heat affected zone (HAZ) cracking in the alloy is the sub-solidus liquation reaction of intergranular M5B3 borides in the material. Further weldability study showed that the HAZ liquation cracking problem worsens with reduction in welding heat input, which is normally necessary to produce the desired weld geometry with minimum distortion. In order to minimize the HAZ cracking during low heat input laser welding, microstructural modification of the alloy by heat treatment at 1080 - 1100oC has been developed. The pre-weld heat treatment minimizes cracking in the alloy by reducing the volume fraction of the newly identified M5B3 borides, while also minimizing non-equilibrium grain boundary segregation of boron liberated during dissociation of the boride particles. Further improvement in resistance to cracking was produced by subjecting the material to thermo-mechanically induced grain refinement coupled with a pre-weld heat treatment at 1080oC. This approach produces, for the first time, crack-free welds in this superalloy, and the benefit of this procedure in preventing weld cracking in the new material is preserved after post-weld heat treatment (PWHT), as additional cracking was not observed in welded specimens subjected to PWHT. en_US
dc.publisher Material Characterization Vol. 65(2012), p. 93 - 99 en_US
dc.publisher Material Science and Technology, Vol. 28, No. 4 (2012), p. 431- 436 en_US
dc.rights info:eu-repo/semantics/openAccess
dc.subject Nickel base alloy en_US
dc.subject Laser beam welding en_US
dc.subject Microstructure en_US
dc.subject Heat affected zone en_US
dc.subject Fusion zone en_US
dc.subject Borides en_US
dc.title A study on laser weldability improvement of newly developed Haynes 282 superalloy en_US
dc.type info:eu-repo/semantics/doctoralThesis
dc.degree.discipline Mechanical and Manufacturing Engineering en_US
dc.contributor.examiningcommittee Cahoon, John (Mechanical and Manufacturing Engineering) El-Salakawy, Ehab (Civil Engineering) Cao, Xinjin (Institute for Aerospace Research National Research Council Canada) en_US
dc.degree.level Doctor of Philosophy (Ph.D.) en_US
dc.description.note October 2012 en_US


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