During the industrial turbine engine operation of the W501F, Row3 Vanes, cracks develop as a result of thermal fatigue. Other damage found is pitting and dents resulting from corrosion/oxidation and FOD (foreign object damage) respectively. Erosion damage is also commonly found on the airfoils. Finally there is downstream deflection of the inner buttress/seal areas, as a result of axial creep. This paper describes the vacuum LPDB (liquid phase diffusion bond) repair process used to repair all of the above-mentioned damage, including LPDB build up and machining of the hook fit areas.
As a means of qualifying the high temperature diffusion bond process, both metallurgical and mechanical property evaluations were carried out. The metallurgical evaluation consisted of optical and scanning electron microscopy. The wide gap diffusion bonded area consisted of a fine-grained structure with carbide and boride phases dispersed both intergranularly and intragranularly. An EDAX analysis was also conducted and the results are reported.
The chemistry of the repaired area is similar to the base metal which may explain why mechanical tests revealed properties equivalent to that of the base metal. The mechanical evaluations undertaken were tensile tests at room temperature and elevated temperature, as well as stress rupture tests. These results were equivalent to mechanical properties of the X-45 Co-based superalloy, which is the base metal of the vane.