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Abstract

The broad range applications of Ultra-Fine Grained metals is substantially limited by the lack of a welding method that allows them to be joined without losing the strong refinement of structure. From this point of view, the solid state welding processes are privileged. Friction welding tests were carried out on UFG 316L stainless steel. A joining process at high temperature activates the recrystallization, therefore the friction welding parameters were selected according to the criterion of the lowest degree of weakness due to recrystallization in the heat affected zone. In order to characterize the structure of basic material and selected areas of the obtained joint, were performed SEM, TEM and metallographic examinations in terms of hardness and range of softening of the material and tensile test. Despite the short time and relatively low welding temperature, results of the test by scanning electron microscopy and transmission electron microscopy confirmed the loss of the primary ultrafine structure in the Heat Affected Zone of welded joint.
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Abstract

Inconel 713C precision castings are used as aircraft engine components exposed to high temperatures and the aggressive exhaust gas environment. Industrial experience has shown that precision-cast components of such complexity contain casting defects like microshrinkage, porosity, and cracks. This necessitates the development of repair technologies for castings of this type. This paper presents the results of metallographic examinations of melted areas and clad welds on the Inconel 713C nickel-based superalloy, made by TIG, plasma arc, and laser. The cladding process was carried out on model test plates in order to determine the technological and materialrelated problems connected with the weldability of Inconel 713C. The studies included analyses of the macro- and microstructure of the clad welds, the base materials, and the heat-affected zones. The results of the structural analyses of the clad welds indicate that Inconel 713C should be classified as a low-weldability material. In the clad welds made by laser, cracks were identified mainly in the heat-affected zone and at the melted zone interface, crystals were formed on partially-melted grains. Cracks of this type were not identified in the clad welds made using the plasma-arc method. It has been concluded that due to the possibility of manual cladding and the absence of welding imperfections, the technology having the greatest potential for application is plasma-arc cladding.
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