Research On Pressurized Electrochemical Nitriding Technology Of 316L Stainless Steel

316L stainless steel has excellent corrosion resistance and excellent overall mechanical properties,but with the development of industry,the service environment it faces is becoming more and more complicated,especially in the marine environment,the corrosion of stainless steel has caused extremely Large economic loss,and at the same time there are great hidden dangers in industrial production,so it is urgent to improve the corrosion performance of stainless steel without reducing its mechanical properties.At present,it is one of the main methods to improve the comprehensive performance of stainless steel by adding N element to steel,but limited by the diffusion of N atoms,the traditional nitriding method has the disadvantages of large energy consumption,low production efficiency and long process cycle.And the dependence on the device also limits its large-scale promotion and use.The development of new nitriding treatment process to improve nitriding efficiency and reduce energy consumption has become the current development direction of stainless steel nitriding technology.Based on the traditional nitriding process,this paper proposes a process to achieve low temperature nitriding of 316L stainless steel.By referring to the treatment methods of electrochemical modification technology and introducing pressure factors into the electrochemical modification technology process,a systematic study The feasibility of this treatment method to achieve low temperature nitriding.Using potentiodynamic polarization test methods,the effects of pressure,processing time and pulse voltage on the corrosion resistance of 316L stainless steel treated by pressurized electrochemical nitriding technology were studied;with the help of scanning electron microscope(SEM)and field Transmission electron microscopy(TEM)and three-dimensional atomic probe(3 DAP)and other methods were used to characterize the morphology and structural composition of the surface layer of 316L stainless steel after surface pressure electrochemical nitriding;in addition,friction and wear experiments and surface hardness were used Test,analyze and study the effect of the treated pattern on its surface properties.The main conclusions are obtained as follows:The effects of different factors on the corrosion resistance of 316L stainless steel during pressurized electrochemical nitriding,including pressure,treatment time and pulse voltage,were studied.The analysis results show that,compared with the treatment method under normal pressure,the treatment under high pressure can greatly increase the pitting potential of 316L stainless steel,indicating that the nitriding layer on the surface of stainless steel can be formed by pressing to improve passivation Stability of the membrane;316L stainless steel was subjected to pressurized electrochemical nitriding treatment at different times,and it was found that only the corrosion resistance of the pattern with a treatment time of 11 cycles was improved.The analysis believes that under the action of a long-term alternating electric field It has a destructive effect on the protective film formed;in addition,in the process of studying the effect of different pulse voltages on pressurized electrochemical nitriding,it was found that the treatment method of applying the cathode voltage alone and the alternating open cycle can also make the 316L stainless steel The pitting potential is significantly increased.It is believed that the cathode voltage in the electric field contributes to the generation of N atoms in the reaction system and accelerates its diffusion to the stainless steel surface,promoting the formation of stable compounds such as Cr2O3 and MoO2 in the passivation film,thus Suppresses the destruction of the passive film by aggressive ions and improves the corrosion resistance of 316L stainless steel.Microstructure analysis showed that 316L stainless steel sample surface subjected to surface pressurized electrochemical nitriding will form a nano-amorphous film layer with a thickness in the range of about 300 nm,and the film thickness is uneven.The results of the three-dimensional atom probe(3DAP)are The higher content of N element in the film layer,where the average N content can reach 0.15%in the thickness range of 0-350 nm,indicating that the pressurized electrochemical nitriding treatment can promote the enrichment of N in the stainless steel film layer and diffuse to the substrate.The friction and wear test results show that the friction coefficient and wear weight of the stainless steel model after pressurized electrochemical nitriding treatment are improved compared with the untreated model,and the tribological performance has been improved.The hardness test also proves this,and the surface hardness of the pattern after pressure electrochemical nitriding treatment has been significantly improved.