Research On Tribological Properties Of FeCrAl Alloy In Dry Environment

In nuclear power plant reactor,the service condition of fuel rod cladding tube is very harsh and complex.It operates in the environment of high temperature,high pressure and strong neutron irradiation.In addition,it is also affected by fluid-induced vibration,alternating load and difference in internal and external pressure.The fluid-induced vibration will cause fretting wear between the fuel rod cladding tube and the positioning frame,which will increase the safety hidden trouble of reactor operation over time.In this paper,the tribological properties of FeCrAl under various motion modes were investigated by setting different parameters and different temperatures in dry environment.New tangential fretting wear equipment,energy control impact wear equipment and energy control impact-shear wear equipment are used in this paper.The tribological properties of FeCrAl alloy under three motion modes were investigated.In addition,the wear profile and wear amount of the wear trace were also measured.The wear mechanism of Fec Cr Al alloy was revealed by comprehensive analysis of the above characterization test results,and the following conclusions were drawn:1.In the study of tangential fretting wear of FeCrAl alloy:(1)Study on the influence of displacement amplitude:When the displacement amplitude is 25?m and 50?m,the F-D curve is linear,and the fretting is in the partial slip zone.The wear form is adhesive wear,and the main damage feature of the sample surface is plastic deformation;when the displacement amplitude is 100?m and 150?m,the F-D curve is parallelogram,the fretting is in the slip zone,and the wear form is abrasive wear.The main damage feature of the sample surface is the furrow.Under the action of large displacement amplitude,the oxidation degree of the sample surface is more serious.(2)Research on the influence of temperature:temperature does not change the fretting state of FeCrAl alloy,but temperature will change the tangential stiffness of FeCrAl alloy during fretting.Except when the displacement amplitude is 100?m,under other parameters,the tangential stiffness at room temperature is greater than that at high temperature.In addition,temperature will change the tangential force during wear.The tangential force at room temperature is greater than the tangential force at high temperature.The wear test results show that the wear of the FeCrAl alloy at high temperature is less than that at room temperature.The reason is that the high temperature causes the Al element to segregate to the surface of the FeCrAl alloy to form a dense oxide film,thereby reducing the wear.(3)Research on the influence of the number of cycles:The jog operation condition does not change with the change of the cycle number,but the load will change the jog operation condition.When the load is 20 N,the fretting is in the slip zone;when the load is 30 N,the fretting is in the partial slip zone.As the number of cycles increases,the amount of wear increases.In addition,the amount of wear at a load of30 N is smaller than that at a load of 20 N,because the increase in load hinders tangential movement.2.In the impact wear study of FeCrAl alloy:(1)Study on the impact of impact energy:FeCrAl alloy exhibits different dynamic responses under different impact energy.The greater the impact energy,the higher the energy absorption rate and the greater the deformation of the contact interface.When the impact energy is 0.27 m J and 0.75 m J,from the results of the three-dimensional morphology,the wear scar is shallow,the circumference of the wear scar is relatively flat,and there are gullies inside the wear scar.When the impact energy is 1.47m J and 2.43 m J,the wear scar area is large,there is a large pit in the center of the wear scar,and the edge of the wear scar is convex,which may be caused by plastic deformation.In the process of impact wear on the grinding pair and the sample,the surface of the material is oxidized and the content of O on the surface increases.In addition,after impact and wear,plastic deformation,pits and peeling occur on the surface of the material.The spalling leads to a reduction in the content of material elements.(2)Research on the influence of the number of cycles:With the increase of the number of cycles,the energy absorption and absorption rate of FeCrAl alloy decrease,the peak impact force increases,and the interface deformation decreases.The reason is that in the process of impact and wear of the material,the surface hardens to reduce wear.In the process of impact wear on the grinding pair and the FeCrAl alloy,the contact interface is continuously oxidized,so the content of O at the wear scar of the FeCrAl alloy increases with the increase in the number of cycles.3.In the study of the impact-sliding wear of FeCrAl alloy:(1)Study on the influence of impact energy:FeCrAl alloy exhibits different dynamic responses in the normal and tangential directions under different impact energy.The greater the impact energy,FeCrAl alloy has higher energy absorption rate in the normal direction,and the greater the interface deformation,the main damage characteristics of the surface are plastic deformation,pits and cracks;the friction coefficient in the tangential direction is reduced;the main damage characteristics of the surface are furrows,Dimples and peeling,etc.In the microscopic morphology of the cross-section,it is found that there is Al₂O₃wear debris accumulation on the surface.(2)The influence of the number of cycles:As the number of cycles increases,the impact force,energy absorption,deformation and friction coefficient fluctuate in a smaller range.FeCrAl alloy wear scar characterization results show that when the number of cycles is 5×10³,the degree of oxidation of the wear scar is the least and no obvious furrow features appear on the surface;when the number of cycles is 10⁴,furrow features appear in the center of the wear scar;the number of cycles is 1.5×10⁴,the center of the wear scar becomes more oxidized.