چكيده به لاتين
In this study, repair welding on the nickel-based superalloy Inconel 939 was investigated and evaluated using three filler metals: IN625, IN617, and C-263, through the tungsten inert gas (TIG) welding method. The project's objectives were initially to determine the optimal welding parameters, followed by examining the effect of the filler metal, and finally assessing the impact of post-weld heat treatment. The innovations in this research include determining the maximum necessary heat input with the least amount of defects formed in various welding regions, as well as investigating the effects of post-weld heat treatment cycles on samples welded with IN617 and C-263 filler metals. The results obtained in this report were evaluated using optical microscopy, scanning electron microscopy, EDS analysis, high-temperature and ambient temperature tensile tests, and Vickers hardness tests to assess microstructure, elemental distribution, and mechanical performance. At the beginning, the superalloy Inconel 939 was considered for 100,000 hours of operation for the base alloy. To improve the microstructure and weldability of the alloy, the workpiece underwent pre-welding heat treatment. To determine the optimal heat input, welding was conducted with IN625 filler metal under four different heat input conditions, revealing that using a current of 60 amps and a heat input of 0.30 kJ/mm prevented the formation of insufficient fusion defects and reduced the number of hot cracks in the heat-affected zone. Subsequently, to investigate the effect of the filler metal, welding was performed with all three filler metals. It was observed that the welded samples with C-263, IN617, and IN625 filler metals exhibited fewer defects and hot cracks in the heat-affected zones, respectively. Finally, to enhance the microstructure and mechanical properties of different regions of the welded alloys, post-weld heat treatment was conducted on the samples in four different cycles, and their properties were compared. Considering the number of formed cracks, the presence of carbides at grain boundaries, variations in hardness profiles in the weld regions, the accumulation of carbide-rich alloying elements, and the size and geometry of γ′ particles in the heat-affected zones, the welded sample with C-263 filler metal subjected to the second type of heat treatment cycle was identified as the optimal sample.
