(Power Generation Materials Group, Korea Electric Power Research Institute)
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Gas turbine blades serviced for a period are usually repaired for reuse via "rejuvenation processes" including fluoride ion cleaning, brazing or welding, and recoating. Among these processes, the welding process is applied to rebuilt damaged parts of the blade in which welding materials being mostly Ni base superalloy are supplied in the form of powder or wire. When powder is used in the welding process, the uniform supply of powder is a very important factor for the uniformity of welding. According to our experience, the uniformity was very poor with the powder supply system only utilizing pressurized air flow. A new powder supply system was developed in which powder is supplied via air flow and simultaneously mechanically. The welding uniformity was much improved with this new system. In this study, the microstructure and mechanical properties of welded parts obtained from several kinds of powder using the new powder supply system were characterized.