Failure investigation on failed inducer blades used in locomotive turbocharger

Inducer blades used in a locomotive turbocharger were found damaged to varying extents servicing for 1000 km. The damages were in the form of fracture, crack and scrape. The fractures show L-shape, which were formed by propagation of axial crack and radial crack. Fractography investigation indicates the multiple origins fatigue is the main failure mechanism of the fractured and cracked blades. Fatigue crack origins are at the blade root with the coarse axial machining marks. The blade root thickness is over-small, which makes the average stress lever at blade root increase. Presence of the coarse axial machining marks at the blade root and over-small thickness of the blade root are responsible for the fatigue failure of the blades. Blades opposite the fractured blades were touched by the worm-shell outside the inducer due to swinging eccentrically of the inducer and the friction between them was operated so that the serious circumferential scrape took place at the edges of the blade-tips.