Abstract
The presence of surface and subsurface residual stresses in steel components has a significant influence on fatigue resistance. In the present work, surface modification of AISI 9254 steel coil springs by heat treatment and multiple shot-peening procedures was investigated. Samples were characterized in the as-coiled, quenched, quenched and tempered, as well as submitted to single and double shot peening treatments. Depth resolved residual stress profiles were determined by X-ray diffraction combined with electrolytic dissolution of the steel. Fracture analysis was performed subsequent to fatigue tests by scanning electron microscopy. It was possible to show that double shot peening led to an increase in compressive stresses in the immediate sub-surface region, which improved fatigue resistance relative to the other tested conditions.
Highlights
In automotive suspension systems, the springs perform the important tasks of supporting vehicle weight and absorbing kinetic energy transmitted from the track to the automobile in the form of elastic strain
The depth resolved variation of residual stresses for samples in the As Coiled (AC), Q, Quenched and Tempered (QT), Single Shot Peening (SSP) and Dual Shot Peening (DSP) conditions are presented in Fig. 2(a) and 2(b)
The elevated tensile stresses present at the surface and sub-surface regions in the Q condition occur because the volumetric expansion caused by the martensitic transformation at the surface outweighs the thermal contraction experienced at the center of the springs during cooling in oil [21]
Summary
The springs perform the important tasks of supporting vehicle weight and absorbing kinetic energy transmitted from the track to the automobile in the form of elastic strain. Given the nature of their operation, automotive springs require excellent fatigue resistance, which is strongly influenced by material surface conditions since fatigue cracks usually nucleate and grow in surface or sub-surface regions. For this reason, various surface treatments are currently applied in the automotive industry with the objective of improving component life or reducing weight by increase in performance [2, 3]. The material undergoes strain-hardening, which increases yield strength at the surface, and the imposition of compressive residual stresses [4] which hinder crack nucleation and growth increasing fatigue resistance, as attested by numerous researchers [5,6,7,8,9,10,11]. Shot peening is a highly flexible process that can be applied to components with various geometries and increases resistance to stress corrosion cracking, fretting and erosion [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
