Failure analysis towards reliable performance of aeroengines

Abstract

Aero-engines are critical components whose reliable performance decides the primary safety of an aircrafthelicopter. This is met by rigorous maintenance schedule with periodic inspection/nondestructive testing of various engine components. In spite of these measures, failure of areo-engines do occur rather frequently in comparison to failure of other components. Systematic failure analysis helps one to identify root cause of the failure, thus enabling remedial measures to prevent recurrence of such failures. Turbine blades made of nickel or cobalt-based alloys are used in aero-engines. These blades are subjected to complex loading conditions at elevated temperatures. The main causes of failure of blades are attributed to creep, thermal fatigue and hot corrosion. Premature failure of blades in the combustion zone was reported in one of the aero-engines. The engine had both the compressor and the free-turbine in a common shaft. Detailed failure analysis revealed the presence of creep voids in the blades that failed. Failure of turbine blades was also detected in another aero-engine operating in a coastal environment. In this failure, the protective coating on the blades was cracked at many locations. Grain boundary spikes were observed on these locations. The primary cause of this failure was the hot corrosion followed by creep damage.