Reason for tooth breakage of the gear shaft end gear disc of the compressor

During the service of a certain compressor, the gear shaft end gear disc on the 5th stage impeller side experienced tooth breakage. The cause of the fracture of the shaft end teeth was analyzed using macroscopic observation, chemical composition analysis, mechanical property testing, scanning electron microscopy and energy spectrum analysis, metallographic examination. The results show that the fracture property of the shaft end teeth was fretting fatigue fracture. During service, insufficient pre tightening force during assembly caused the center pull rod to relax, resulting in fretting wear of the tooth surface. Cracks originated from the pits formed by micro motion wear. Under the action of alternating loads, stress concentration occurred at the pits, led to the initiation and propagation of fatigue cracks, ultimately resulted in the fracture of the shaft end teeth.