Study On The Impact Fretting Wear Behavior Of 304 Stainless Steel And 690 Alloy Thin Wall Tubes

When a nuclear power plant is in operation,the heat transfer tubes in the steam generator are servicing in extremely complex environments.The Flow-Induced Vibration(FIV)within the steam generator system is unavoidable,and there are many modes of friction and wear in heat transfer tubes during service.For example,impact wear,tangential wear,and various compound wear.If the heat tube in the steam generator seriously damaged,it will cause nuclear leakage and contamination of the coolant,which will seriously shorten the service life of the nuclear power plant and lead to serious economic losses.The focus of this article was that the heat transfer tube was subject to slight impact wear and used a new impact wear tester.The effects of parameters such as the support angle of the anti-vibration bar,the pre-compression stress,the tube length,the cycles and the initial velocity on the impact wear behavior of the heat transfer tube are studied.In addition,the 690 alloy was subjected to ultrasonic nano-surface rolling treatment to compare the damage behavior of the nano-surface and the original surface under impact.During the test,contact mechanics response,energy dissipation,etc.are analyzed during the impact process.After the test,the microscopic appearance of the wear scar is analyzed by using optical microscope,SEM electron microscope and matched EDX,EBSD,and Contour GT.Systematic studying on failure mechanism of heat transfer tube impact wear.The main conclusions can be draw as following:(1)Studying the effect of different supporting angles on impact wear of 304 stainless steel thin-walled pipe.As the support angle increases,the deformation and impact contact time of the 304 stainless steel tube increase.However,the peak contact force and energy absorption reduced.Through the microscopic analysis of wear scars,it founded that when the support angle increases,the degree of wear of the material decreases,which found that the wear mechanism of the 304 stainless steel tube was fatigue spalling.(2)Analyzing the effect of compressive stress on the impact wear behavior of 690 alloy thin-walled pipe.it found that the magnitude of pre-stress has a greater impact on the dynamic response and wear of the material.As the pre-stress increases,the impact deformation of the pipe decreases,but the impact contact force peak and wear scar area increase.The study found that the energy absorption rate decreases with the increase of pre-stress.When the preload reached 1000 N,the energy absorption rate no longer decreases,and reached a balance.The impact abrasion mechanism of the Inconel 690 thin-wall tube was mainly fatigue exfoliation and oxidation wear.(3)Ultrasonic surface rolling processing(USRP)was used to nanometerize the surface of the 690 alloy thin-walled tube sample for impact abrasion test,and compared with the untreated surface.Hardness tests performed along the depth direction of the untreated sample and the nanometer sample cross-section.The results showed that the thickness of the hardened layer was approximately between 300μm and 400μm,and compared with the original material,under the same impact wear parameters,the peak contact force increases,the deformation variable decreases,and the wear resistance of the material increases.This was because the nano-hardened layer helps to improve the local hardness and structural rigidity of the material surface,and directly reduces the energy used for material wear,thereby reducing the degree of wear of the nano-sized sample.The surface nanocrystallization of the material can improve the microhardness and anti-contact fatigue properties of the material surface,which can effectively improve the surface wear resistance,and reduce the occurrence of fatigue cracks.