Braze repair of MA754 aero gas turbine engine nozzles

Abstract

MA754, an oxide-dispersion strengthened nickel-base superalloy, is the vane material being used in the High Pressure Turbine (HPT) Nozzle of the 11404-400 turbofan engine. Thermal fatigue cracks are known to develop in the nozzle vanes during service and the component replacement costs can, in general, be very high. Attempts to demonstrate the feasiblity for braze repair of MA794 have thus far yielded little success. An experimental program aimed at developing a braze repair procedure for healing cracks in MA74 HPT nozzles is described. Thirteen different braze compositions, using two different brazing times and gap widths, are evaluated. Fxperimental results are described detailing the microstructure, degree of oxide agglomeration and porosity in the region of the brazed joints. The feasibility of applying a braze repair procedure to the nozzle component is discussed.