Crystallographic, Microstructural, and Mechanical Characterization of Dynamically Processed EP741NP Superalloy
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EP741NP alloy is a high-performance Ni-based superalloy that has unique applications in the areas where high temperature and corrosion resistance are the pre-requisite. EP741NP superalloy exhibits excellent mechanical strength and good structural stability at elevated temperatures.[1,2] The structural components made of this superalloy are used in aerospace industry, cryogenic storage, gas turbines, jet engines, rocket motors, and nuclear reactors.[3] The superalloy is synthesized in powder form and thereafter consolidated as a solid monolith for the industrial use.[4] The normal fabrication route for obtaining monoliths from particulate material has two important aspects: the elimination of pores and creation of bonds between the particles.[5,6] Preferred bonding mechanisms are mechanical welding and interlocking of particle surfaces. The first requires plastic flow in order to break down the surface oxides; the
A.D. SHARMA, Assistant Professor, is with the Department of Physics, MLSM College, Sundernagar, India. A.K. SHARMA, Scientist-G, is with the Snow and Avalanche Study Establishment, Chandigarh, India. N. THAKUR, Professor is with the Department of Physics, Himachal Pradesh University, Shimla, India. Contact e-mail: [email protected] Manuscript submitted December 27, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
second depends on the irregular surface geometry. Hard, smooth, and spherical particles (as in the present case) do not permit either of these mechanisms because after compaction, they simply fall apart again. Such powders must be contained in a capsule and after compaction must be bonded by sintering or hot-pressing. The consolidation of powders using traditional metallurgical methods faces number of difficulties due to high capital investment, long processing time, formation of inter-metallic compounds, etc. Prolonged high temperature exposure destroys the rapidly solidified fine microstructure and thereafter leads to grain growth as such dynamic powder consolidation is a promising approach to overcome these difficulties and is of particular interest to the material scientists and engineers.[7] Explosive shock wave produces quasiadiabatic heating on the surfaces of particles without superfluous heat input that might jeopardize the meta stable structure in the interior of the particles thus maintaining a relatively cool temperature at the particle interior.[8] This process is a thermo-mechanical treatment and therefore post-deformation sintering is not required.[9] This is a single-stage processing technique with scale-up advantage.[10] When shock wave traverses through the powder, it causes interparticle friction, jetting, and particle deformation resulting into bonding. This is a rapid fast technique to obtain monoliths of a particulate material and offers no time for grain
growth.[11] The major advantage of explosive shock wave compaction is its controlled detonation pressure that could enhance the efficiency of final product and facilitate grain refinement.[12] A lot of experimental work has been d
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