Failure Investigation on Inducer Blades of Locomotive Turbocharger
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TECHNICAL ARTICLE—PEER-REVIEWED
Failure Investigation on Inducer Blades of Locomotive Turbocharger Zhi-wei Yu • Xiao-lei Xu
Submitted: 20 September 2009 / in revised form: 16 October 2009 / Published online: 2 December 2009 Ó ASM International 2009
Abstract Damage to varying degrees including fracture, cracking, and scraping occurred on inducer blades used in a locomotive turbocharger which had run for 3626 km. The blade fracture was formed by the propagation of axial and radial cracks forming an L-shape. Fractography investigation indicates that the axial fracture mode of the blade was by fatigue. The radial fracture was formed by one instantaneous crack. A strike dent was present on the leading edge of the fractured blade and this dent became the initiation site of fatigue crack. Failure of other blades was subsequent to the original fracture. Keywords Inducer blades Multiple origins fatigue fracture Strike dent Failure analysis
surface damage analysis were performed to determine the cause of failure.
Experimental Methods The chemical composition of the failed inducer material was determined by spectroscopic chemical analysis method and the microstructure of blade material was determined by optical microscopy (OPM). The fracture surfaces and damage morphology on blade surfaces were analyzed by visual observations and scanning electron microscopy (SEM).
Results and Discussion Introduction The inducer blades used in a locomotive turbocharger were damaged to varying degrees when a failure occurred after the engine had run for 3926 km before failure. It was reported that a major repair had been conducted on the turbocharger once and the inducer was re-assembled after being repaired. The repaired turbocharger was then sandblasted using Al2O3 grit. The failed inducer blade is made from an LD5 Al-base alloy. The specified mechanical properties are rb C 380 MPa, rs C 275 MPa, d C 10% and HB C 110. In this paper, fractographic investigation and
Z. Yu X. Xu (&) Electromechanics and Material Engineering College, Dalian Maritime University, Dalian 116026, P.R. China e-mail: [email protected]
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The failed inducer contained 10 wide blades and 10 narrow blades distributed alternately as shown in Fig. 1. The wide blades were labeled as illustrated. Fracture, cracking, scraping, and strike marks occurred on the wide blades. No severe damage was found on the narrow blades. Examination of the remains of the failed inducer showed that blade A was fractured completely at airfoil and bending-fracture occurred at the blade-tips of blades B, C, and D (Fig. 1). The fracture of blade A exhibits L-shape crack (Fig. 2), which means that the fracture surface formed by propagation of the axial crack (A1) and the radial crack (A2). The surface of fracture A1 is relatively smooth, but the shear tearing traces were found on the fracture A2 close to the convex side. The color of fracture A1 close to the leading edge is dark, but the color of the low portion of fracture A1 and fracture A2 is light, suggesting that crack A2 occu
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