Study On The Corrosion Resistance Influencing Factors Of 17-4PH Aviation Fasteners

In the modern aerospace industry,17-4PH stainless steel is widely used in fastener materials due to its excellent properties.Stainless steel fasteners are highly susceptible to corrosion and fractures due to the influence of the marine atmospheric environment,posing a major safety hazard to flight safety.Therefore,this paper starts from the manufacturing process of 17-4PH aviation fasteners,based on the heat treatment system,defect scale removal method and surface post-treatment method to explore the influence of different processes on its corrosion resistance,which has important reference value for improving the corrosion resistance of 17-4PH aviation fasteners.Firstly,this paper changes the microstructure of the 17-4PH aviation fasteners by optimizing the heat treatment system to improve the corrosion resistance:(1)The effects of different aging treatment temperatures of 480?-560°C on the corrosion resistance and hardness of stainless steel were investigated.The results show that the corrosion resistance is the best and the hardness is the highest when the aging temperature is 480°C.(2)Introducing adjustment treatment between solid solution and aging treatment,and investigating the effect of different adjustment treatment temperatures on the corrosion resistance and hardness of 17-4PH stainless steel at785?-845°C.The results show that the introduction of the adjustment treatment greatly improves the corrosion resistance of 17-4PH stainless steel,but the hardness of the material is reduced.The corrosion resistance is optimal when the treatment temperature is adjusted to 845°C.Secondly,for the removal method of the defect scale:(1)The necessity of removing the original defect scale by some means was verified by SEM and EDS;(2)For the specific removal method of defect scale,the optimum process parameters of electrolytic pickling were determined by experiment:current density 8A/dm~2,electrolyte temperature 75°C,electrolyte concentration 15%;(3)Investigating the effect of different ultrasonic cleaning synergistic electrolytic pickling methods on surface defect scale removal efficiency.Moreover,the ultrasonic electrolysis alternately treatment at 35°C can completely replace the electrolysis treatment at75°C.Finally,in this chapter,different blasting conditions,oxidation temperature and holding time were used to prepare dense scale on the surface of 17-4PH stainless steel.The corrosion resistance was investigated by electrochemical experiments and neutral salt spray experiments,microscopic and phase analysis were performed by SEM and XRD.It is concluded that:as the oxidation temperature increases and the holding time is prolonged,the corrosion resistance of the scale is improved.In addition,the corrosion resistance of the scale prepared after dry blasting pretreatment is further improved than which without dry blasting.