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Plasma transferred arc welding (PTA) has been considered a promising process to restore worn areas of land-based gas turbine blades and vanes.The objective of this investigation was to study the effect of PTA welding on the repairing of IN-738LC superalloy components. Tensile tests were conducted on specimens welded with various combinations of parameters. Room temperature, 760 ~ and 980 ~ were selected as tensile test temperatures. High-temperature phase transformed, during solidification, were identified by differential thermal analysis (DTA). The weld-pool shapes and microstructures of welded specimens prepared by various welding parameters were evaluated by optical metallography (OM), a scanning electron microscope (SEM) equipped with energy dispersive x-ray spectrometer (EDS), and microhardness testing.Results of this study showed that PTA welded specimens exhibited 96% nominal tensile strength of IN-738LC base materials. Specimen failure was observed predominantly in the base materials instead of in the heat-affected zone (HAZ) for gas tungsten are weld (GTAW) repair weldments. IN-738LC is considered susceptible to weld cracking during fusion welding; however, using a low-input heat repair welding process (PTA), cracking susceptibility could be minimized by the optimized welding parameters.i

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Duplex Zr02-8 wt % Y2O3/Ni-22Cr-1OAI-1Y thermal barrier coatings (TBCs) on Mar-M247 superalloy were tested under different operating conditions within the temperature range 1000" to 1150°C. Results of experiments in this study show that oxidation of bond coatings is the dominant TBC degradation mechanism whereas the operationally induced stresses exert a conjugate effect. The mechanisms of sintering and phase transformation of top coatings do not contribute to failure of TBCs within the temperature range studied. NiO and Ni(Cr,Al)204 grown on the surfaces of the bond coatings seem to accelerate spalling of the top coatings along a top coating/ bond coating out-grown oxide interface. However, it is also concluded that the lifetime of TBCs is not directly related to a critical specific weight gain under thermal cycling conditions. [