Failure of the J79 Engine Compressor Blade Due to Stall

Abstract

The fractured and damaged compressor rotor blades of a J79 engine have been examined. Optical, stereoscopic, microhardness testing, and SEM examinations were carried out to find out the causes of the fracture. The material of the blades was STS403 and blades were used without coating. From the 15th through the 17th compressor stages the rotor blades, stator vanes, combustion, and turbine sections were damaged. The fractured surface of the 17th blade show multiple origins, secondary cracking in the blade's convex surface, and extensive propagation before separation and rougher surfaces. The metallographic analysis of the microstructure suggested work hardening. Based on the results, the cause of the fractured blade was highamplitude fatigue, due to severe stall. After normal engine usage of 5 months, the blade fractured and blade fragments hit the other compressor blades, stators, and casing, and caused damage in both combustion and turbine sections.