Improving Repair Quality of Turbine Nozzles Using SA650 Braze Alloy

Abstract

Due to competitive pressures, airlines are requesting that engine manufacturers reduce cost of ownership for their products. Developing repairs instead of replacement, and enhancing repairs already available, are key methods to do this. Airfoil components of high pressure and low pressure turbines are subject to wear and replacement due to thermal fatigue and oxidation. These are the highest cost items for maintenance and replacement and thus repairs for these components were among the first to be developed. Initially these parts were repaired by Gas Tungsten Arc (GTAW) welding, however, yields were low and part performance was degraded by the metallurgical degradation of the weld heat affected zone. The next improvement in repair was the development of the brazing process known as Activated Diffusion Healing (ADH). By cleaning and brazing the cracked areas, many parts were successfully repaired and returned to service. Now, GE Engine Services has developed a more advanced brazing alloy, SA650, which is a significant improvement in strength over older brazing alloys while offering superb resistance to high temperature oxidation. This provides higher tensile and creep strength in the repaired component, allowing improved performance and increased time on wing before cracking reoccurs and repair again becomes necessary. This is an example of the overall strategy of GE Engine Services to expand the number and quality of repairs offered to its customers.