Investigation Of Laser Shock Peening On Corrosion Fatigue Resistance Of 2Cr13 Stainless Steel

Nowadays,lots of key components are prone to fracture under corrosive conditions with being limited by complex service environments in the industrial production.It makes a huge economic loss.One of the core scientific problems in modern mechanical component remanufacturing is how to use advanced surface treatment technologies to strengthen key components in order to extend service life and improve the use reliability.Laser shock peening(LSP)is a novel surface strengthening technology which uses high-energy laser pulse to induce shock wave pressure.Besides,it can make high strain rate of plastic deformation on the material surface in a very short time and also effectively improve the stress distribution of metal materials.What’s more,LSP optimize the surface microstructure observably so as to impede the corrosion fatigue crack formation,improve the service life of components.In allusion to the problems mentioned above,in this dissertation,the samples of 2Cr13 martensitic stainless steel are regarded as the study subjects treated by laser shock peening to investigate the characteristics of corrosion fatigue crack growth.Then the effects of different LSP parameters on the corrosion fatigue properties have been further discussed with experimental analysis,the enhancement mechanism has been described in detail with macrostate and microtopography.And the corresponding numerical simulation of residual stress field has been completed.Some important conclusions and achievements of this work are listed as follows.(1)The digital analysis based on ABAQUS has been established and the residual stress distribution has been obtained visually.Combined with the data of the simulation analysis,the suppression of corrosion fatigue crack growth has been studied by digital rule analysis.The simulation results are in good agreement with the experimental results,which can be used to effectively study the characteristics under the residual stress field induced by laser shock peening.The stress state of model changes obviously.In addition,the residual stress field of section shows a symmetrical distribution.(2)The effect of laser shock peening on corrosion fatigue life and crack growth has been investigated by experimental study,including influences of different LSP impacts and corrosive medium concentration.The experimental data have been analyzed and summarized,a law of crack growth has been revealed quantitatively by curves.The corrosion fatigue life of samples increase and the crack growth rates decrease with increasing LSP impacts.The corrosion fatigue life is shortened with increasing concentration which makes material fracture easily.Based on the Paris formula,the changing law of material constants has been obtained.Last but not least,the gain mechanism of laser shock peening on corrosion fatigue life has been summarized.(3)The morphological characteristics of fatigue fracture strengthened by LSP are also deeply analyzed with macroscopic morphology and micro-strengthening mechanism.The differences of crack sources make localized plastic deformation which leads to the irregular fracture surface.The fracture surface of untreated samples are smoothed while the fracture surface of LSPed samples are rough and uneven with cleavage steps,river patterns and tearing ridges.The path of crack growth becomes much more tortuous,which consumes plentiful strain energy,hinders crack growth and reduces the crack growth rate.The degree of corrosion has been reduced by LSP with comparing the changes of main elements in the fracture.(4)The surface integrity and mechanical properties of 2Cr13 stainless steel have been studied.The results show that the amount of plastic deformation on surface increases with increasing LSP impacts.In other words,it means that the resistance to plastic deformation has been strengthened.The influence of LSP on residual stress has been analyzed.The results show that the compressive stress increases with increasing LSP impacts.Crack initiation is restrained availably and crack growth rate is reduced by compressive stress.The corrosion fatigue resistance of material improved by forming crack growth resistance.In summary,a new way for how to improve the corrosion fatigue resistance of key components has been provided in this dissertation.It helps to deepening understand the improvement of 2Cr13 stainless steel mechanical properties,which provides theoretical and experimental basis for the plastic deformation strengthening mechanism.