Studies On Microstructure And Properties Of Crack Tip In Remanufacturing Blank With Electropulsing

Remanufacturing can minimize the negative impact of manufacturing on the environment, and make use of raw materials and energy efficiency the highest. Member of cracks appearing in the national economy development and labor accident prevention have played a significant impediment. For some large mechanical components containing cracks, in order to prevent the protection of resources, waste of energy and the environment, only to repair cracks can ensure the smooth progress of the follow-up process of remanufacturing, cracks repair plays a vital role in the remanufacturing process.In this paper, using high energy pulse current impacting device to process 316 austenitic stainless steel which containing prefabricated unilateral fatigue crack. Using metallographic microscope, X-ray diffraction, electron backscattered diffraction (EBSD), transmission electron microscope (TEM), and other modern testing means to study the influence of high density pulse electric current to the microstructure in crack tip regions, to analysis the process of evolution of melting and heat treatment.The study found that the current flow occurred concentration phenomenon around the crack tip after the pulse current processing, so that the crack tip melted to form a melt hole, with the increase of the input voltage or the capacitance, the melt hole size larger, reduced the stress concentration phenomenon of the crack tip.The phase of the crack tip has not changed after the pulse current handling. The instantaneity of pulse current makes the crack tip organizations gradient occur, including the columnar grain zone, equiaxed recrystallization region and the substrate region. Plastic deformation occurred in the pre-cracking process made the samples stored a certain amount of energy so as to provide a driving force for the pulse current process recrystallization, deformation of the original sample was recrystallized grains gradually substituted grains, the characteristics of rapid heating and rapid cooling of pulse current suppress recrystallization grain growth to achieve the purpose of grain refinement to improve the mechanical properties of the material.The dislocation density of the crack tip region reduced and the dislocation tends to parallel distribution to shift from complex tangled untreated ago after the pulse current handling. Pulse current promoted the dislocation motion, made the dislocation density gradient increased, reduced the recrystallization temperature, and is conducive to the recrystallization process.The tensile strength and elongation of two material samples varying degrees have been improved after the pulse current handling, of which the highest tensile strength of austenitic stainless steel 316L increased 6.06%, the elongation increased 18.76%, the tensile strength of incone1625 nickel-based superalloy increased 21.10%, the highest elongation increased 13.51%.