| 304L stainless steel is widely used as an engineering material in mechanical engineering,coastal equipment and construction.Coarse grained 304L stainless steel has limited its application in related fields due to its relatively low strength.Ultrafine grains can effectively improve the strength of the metallic material,the introduction of lamellar structure can significantly improve the ducility of the metallic material,which has been applied in the heterogeneous lamellar Ti,so whether the combination of ultrafine lamellar grained structure can improve the strength and ducility of 304L stainless steel to be studied in depth.When304L stainless steel is used as a mechanical component,it also faces the problem of frictional wear or pitting resistance,so it is of great importance to study the preparation and properties of ultrafine lamellar grained 304L stainless steel.In this paper,we select industrial 304L stainless steel as the object of study,using cold rolling and multi-directional hot forging preparation means,analysis of the preparation process on the influence of microstructure,to explore the microstructure changes on its microhardness,tensile properties,friction wear and other mechanical properties and pitting resistance of the evolution of the law,and then analyse the friction wear properties and pitting resistance of the formation mechanism.The main findings of the study are as follows.（1）The cold rolling and multidirectional hot forging processes were used to prepare 304L stainless steel with ultrafine lamella grain,and the microstructure of the stainless steel was analyzed using XRD,SEM,EBSD and TEM and other related equipment.The results show that both the cold rolling process with 70%rolled volume and the multidirectional hot forging process can prepare ultrafine lamella grain304L stainless steel with layer thickness of 200-400 nm,while the organization of 304L stainless steel after multidirectional hot forging is almost the same as the original coarse grain,which consists of a single austenite,while the 70%cold rolled sample consists of martensite.（2）By comparing the microhardness and tensile properties of the preparation process,the results show that the microhardness of ultrafine lamella grain 304L stainless steel prepared by the multidirectional hot forging process is～312 HV,while it has a good strength-ducility match（yield strength of～750 MPa,uniform elongation of～39%）,the effect of grain refinement and dislocation strengthening significantly increases the yield strength,while the strain The strain-induced martensitic transformation increases tensile plasticity and has a good ability to inhibit crack extension,with a ductile fracture mechanism.In dry conditions,the wear mechanism is more slightly oxidative and more moderate adhesive wear mechanisms;in high humidity conditions,the wear mechanism is oxidative and slightly adhesive wear mechanisms.In high humidity wetting conditions,the surface of the abrasion marks exhibits only slight plastic deformation.（3）The conventional three-electrode electrochemical test system was used to select ultrafine lamella grain 304L stainless steel,and the corrosion behavior and pitting mechanism of pristine coarse crystalline and ultrafine lamella grain 304L stainless steel in 3.5wt.%NaCl solution at room temperature were revealed by comparing the corrosion behavior of the surface and cross-section of the pristine coarse crystalline and ultrafine lamella grain 304L stainless steel.The study shows that the ultrafine laminated cross-section samples have better pitting resistance with a maximum breakdown potential Epof 293 mV,a corrosion point of-117 mV and a corrosion current of 1.0×10-7A/cm2.The enhanced pitting resistance of the ultrafine laminated cross-section samples is mainly due to the high density grain boundaries in the ultrafine laminated cross-section that can promote the diffusion of Cr to the corrosion surface,increase the diffusion of Cr rate and promote the ability of Cr-rich passivation film regeneration. |
