316不锈钢的超细微粒及复合强化喷丸研究OA

This study systematically investigates the effects of ultrafine particle shot peening(UFSP)and composite shot peening(CSP)on the surface integrity,mechanical properties,and corrosion resistance of 316 stainless steel,so as to address the significant research gap in the application of sub-10 µm particles and multi-step peening sequences.The originality of this work lies in the direct comparison of single peening using 80 µm(micro)and 10 µm(ultrafine)particles with a novel composite process(80 µm followed by 10 µm),under controlled pressures(0.2 MPa and 0.4 MPa),coupled with a post-peening tempering treatment(300℃for 30 min)to assess thermal stability.The experimental methodology involves preparing 15 mm3 specimens from commercial 316 stainless steel under six distinct peening conditions:Micro-0.2,Micro-0.4,Ultrafine-0.2,Ultrafine-0.4,Composite-0.2,and Composite-0.4.A comprehensive characterization suite is employed:surface morphology and roughness(Ra)via profilometry,microstructure analysis by Scanning Electron Microscopy(SEM)and Transmission Electron Microscopy(TEM),surface residual stress via X-ray diffraction(XRD),microhardness profiling from the surface to the interior,and electrochemical polarization curves to evaluate corrosion behavior.Crucially,TEM is used to analyze dislocation structures before and after tempering.Key findings reveal distinct advantages for each process.UFSP produces the superior surface finish,with the lowest average roughness(Ra=1.03-1.06 µm),attributable to the fine,shallow,and densely distributed craters observed by SEM.This results in the best corrosion performance,evidenced by the highest corrosion potential and lowest current density in polarization tests,as the minimal impact energy preserves the protective passive film.However,UFSP induces a relatively shallow hardening layer(30 µm depth,max hardness 300HV)and exhibits the most significant stress relaxation after tempering(residual stress reduction>50%),indicating lower microstructural stability.Conversely,the novel CSP strategy yields the most favorable combination of properties.It achieves a high surface residual compressive stress of ‒993 MPa and the highest surface microhardness,nearly doubling the base material's hardness to 500HV,with a substantial hardening depth of 70 µm.SEM images confirm that the secondary UFSP step partially smoothes the craters formed by the initial micro-peening,resulting in a surface roughness intermediate between the two single-step processes.Notably,CSP samples demonstrate superior resistance to stress relaxation during tempering compared with UFSP,suggesting a more stable deformed layer.TEM analysis of the subsurface(15 µm depth)reveals high-density dislocation tangles and strain-induced martensite formation,particularly prominent in Micro and CSP samples.The CSP process facilitates the formation of a gradient nanostructured layer,enhancing mechanical stability.The study establishes that output pressure positively influences residual stress and hardness,with 0.4 MPa conditions generally outperforming 0.2 MPa.The significant stress relaxation in UFSP samples upon tempering is linked to the lower stability of its dislocation structures and finer deformation layer.In conclusion,this research demonstrates that UFSP is optimal for applications demanding exceptional surface smoothness and corrosion resistance.In contrast,the innovative CSP process offers a superior solution for components requiring a synergistic combination of high compressive residual stress,significant surface hardening,considerable hardening depth,improved surface finish compared with conventional peening,and enhanced thermal stability.These findings provide critical insights for selecting and optimizing peening parameters for 316 stainless steel in high-precision fields such as medical devices and aerospace components.