Failure analysis of a passenger car coil spring

Investigation on the premature failure of suspension coil spring of a passenger car, which failed within few months after being put into service, has been carried out. Besides visual examination, other experimental techniques used for the investigation were (a) microstructural analysis and fractography by scanning electron microscopy (SEM), (b) inclusion rating by optical microscopy, (c) hardness testing, (d) residual stress measurement by X-Ray diffraction (XRD) and (e) instrumental chemical analysis. Inherent material defect in association with deficient processing led to the failure of the spring.