Study On Impact-sliding Wear Mechanism Of Several Typical Metal Materials In Nuclear Power Plants

At present,China's nuclear industry is in a rapidly developing stage now.During the "Thirteenth Five-Year Plan" period,the country's nuclear power was put into operation at about 30 million kilowatts,and projects now under construction will be reached more than30 million kilowatts,the installed capacity in 2020 will more than sixty million kilowatts.Steam generators as one of the critical component of nuclear power plants,can not only directly affect the efficient at generating electricity,but also hinder the diffusion of radioactive substances,which is very important for the safe and efficient operation of nuclear power plants.However,due to flow-induced vibration,neutron radiation,temperature differential,and fluid pressure,various complex friction and wear behaviors can potentially occur among the tube and its support plate.Over time,the local thinning and even rupture will occurs in tubes which greatly increase the number of potential safety problems in nuclear power plants.Therefore,through investigation and analysis the wear behavior and damage mechanism of steam generator tubes under different working conditions can provide theoretical support and reference values for the anti-wear design of nuclear power components,and is of great significance for improving the efficiency and safety of nuclear power plants.At present the study of wear behavior of nuclear materials at home and abroad mainly focus on the forms of sliding wear,there are few reports on the radial impact or impact-sliding wear.Mainly due to the impact-sliding wear process is more complicated than others,including the dynamic mechanical behavior,energy dissipation,interface deformation and others.In this paper,based on the self-made impact-sliding wear test device,the effect of impact velocity,sliding velocity,mass of impact block on the impact-sliding wear behaviors of several typical nuclear materials are systematically studied.Dig deep into the changes of mechanical response,interface deformation,energy dissipation,wear mechanism among each experimental.All of this works can offer scientific basis and methodological support for effectively solving the wear problems that occur during the service life of nuclear materials.The main work and conclusions of this paper are as follows:(1)A novel impact-sliding wear test rig was developed,which provides an experimental basis for studying the impact-sliding wear behaviors of nuclear materials.This research breaks the traditional design ideas of friction-wear testers,introduces many innovative design and technology to develop a novel impact-sliding wear test rig.The motion state of test sample and friction pair can be controlled individually.Various experimental results can be obtained,and all test results are of good comparability and reproducibility.(2)Impact-sliding wear response of 2.25Cr1 Mo steel and 304 SS under ball-plane contact modeThe self-made impact-sliding wear test rig was used to investigate the wear behavior of these two steels in ball / plane contact mode.The effects of different impact and sliding velocities on the dynamic mechanical response and damage mechanism of these two steels are detailed analysis.The increase of impact velocity will cause the deformation of the contact interface,the normal impact force and the tangential friction force.The higher the sliding speed,the more frictional dissipation energy and wear degree will be.(3)Systematic study the impact-sliding wear behavior and damage mechanism of2.25Cr1 Mo tube.The self-made impact-sliding wear test rig was applied to investigate the dynamic wear behavior and damage mechanism of 2.25Cr1 Mo tube in the column / tube contact mode.How the mass and initial velocity of the impact block,the sliding velocity of the tube influence the normal force,compression displacement,tangential friction force,and response time are analyzed.The results show that the increase of the initial velocity of the impact block or its mass will lead to the increase of the impact force,compression displacement amplitude and friction force during the wear process;the increase of the tube's sliding velocity will increase the friction force;the contact response time increases with the mass of the impact block,but decreases with the increase of its initial velocity,regardless of the tangential velocity of the tube sample.The wear degree of test samples is different under each experimental parameter,the damage mechanism is mainly represented by fatigue wear,oxidative wear and delamination of the surface.The improved semi-analytical finite element method was applied to establish the elastoplastic impact-sliding contact model.The model was used to simulate the impact-sliding wear test under different parameters.The contact stress,wear depth and wear area were calculated.All numerical results are in good agreement with the corresponding experimental results.(4)Effect of USRP on the impact-sliding wear behavior of Inconel 690 alloy tubeThe surface of Inconel 690 alloy tube was treated by USRP technology.The changes of the surface morphology,microstructure,and mechanical properties were analyzed.The results showed that the surface roughness is significantly reduced after treated,the surface Micro-hardness and residual compressive stress are greatly improved,and the surface grain is obviously refined.All these can be attributed to the combined effect of complex stress state and strong plastic deformation induced the grain dislocation and movement more frequently,t which will lead to the formation of sub grains,and these grains grow into new grains,thereby refining the grains.The impact-sliding wear behaviors of the USRP treated and untreated Inconel 690 alloy tube were investigated by the self-made wear test rig.All results show that the wear resistance of the USRP treated sample is significantly improved.