Abstract
The effects of surface softening on fatigue behavior of AISI 316L stainless steel were investigated. Using cold-rolling and electromagnetic induction heating treatment, a gradient structure was fabricated on AISI 316L stainless steel within which the grain size decreased exponentially from micrometers to nanometers to mimic the surface softening. Stress-controlled fatigue tests were applied to both the gradient and homogeneous structures. Compared with the homogeneous sample, surface softening had no evident effect on fatigue behavior when the stress amplitude was greater than 400 MPa, but significantly deteriorated the fatigue behavior at stress amplitude ≤400 MPa. At high-stress amplitude, fatigue behavior is dominated by crack propagation. When the stress amplitude is lowered, strength reduction and stress concentration caused by surface softening accelerate crack initiation and propagation, resulting in an inferior fatigue behavior.
Highlights
Softening on the this section, the effects of surface the fatigue was behavior were analyzed in In various stress amplitudes, insurface terms of crack initiation fatigue behavior were analyzed in various stress amplitudes, in terms of crack initiation amplitudes, terms of crack initiation and propagation, cyclic deformation behaviors, and residual stress
The results showed that the showed that the surface softening layer underwent significant work hardening during surface softening layer underwent significant work hardening during fatigue, and work fatigue, and work hardening helped restrain growth of fatigue cracks
By using a gradient structure, the effect of surface softening on fatigue performance was studied
Summary
Optimization of the surface structure and properties may effectively enhance the global behavior of a material and its service lifetime [3,4,5]. Surface strengthening technology such as shot peening [6,7,8], surface mechanical attrition treatment [1,9,10,11], surface mechanical rolling treatment [2,12,13], and surface mechanical grinding treatment [14,15,16]. Grain coarsening is common in nanograined metals under tension [15], compression [19], or cyclic loading [14,20,21,22]
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