Research On Rolling Wear Properties Of Laminar Plasma Spot Quenched Wheel/Rail Materials

Nowadays,with the rapid development of social science and technology,the railway transportation industry has been is also developing in the direction of high speed and heavy load with overwhelming demands from industries and passengers.However,due to the complex operating environment and rigorous operating conditions of high-speed trains,the wear and contact fatigue between the train wheels and the rail has become one of the key factors affecting the operation stability,and safety of trains as well as the service life of train wheels.In this paper,a new surface treatment method for high-speed wheel/rail materials is adopted to improve the wear resistance: laminar plasma spot quenching technology.The spot quenching treatment of the ER8 wheel steel and U71 Mn G rail was carried out by plasma generator.A series of regular hardening zones were formed on the surface of the material.The regions were heated to the austenitizing temperature at a very fast rate and cooled quickly,and the phase transformation strengthening occurred,thereby increasing the hardness in order to strengthen the surface of the wheel and rail materials.With testing using the MJP-30 rolling contact wear tester,the effect of laminar plasma quenching distance and treatment area ratio of laminar plasma quenching on the surface friction and wear properties of wheel/rail specimens was studied.The wear mechanism of wheel-rail materials was investigated via microscopic morphology observation,profile damage observation,hardness detection,SEM and other technologies.On the basis of the above research,the optimized quenching process parameters are finally formed,which provides new engineering solutions and options for effectively improving the wear resistance of high-speed train wheel/rail materials.The main research conclusions of this paper are as follows:Laminar plasma spot quenching treatment can significantly improve the wear resistance of high-speed wheel/rail materials.After quenching,dense martensite structure is formed on the surface of the material.The microhardness is increased by more than 2 times,and the total wear rate can be reduced by more than 80% under the condition of 5% slip rate.Moreover,the laminar plasma surface spot quenching can improve the damage form of wheel and rail materials.The crescent hardening zone formed after quenching has good coordination and bonding force with the substrate,which can resist the plastic deformation and crack propagation of the material.The impacts of quenching distance and surface quenching area ratio on the wear properties of wheel/rail materials have significant differences.Under the condition of avoiding overburning of the samples,the wear resistance of wheel/rail material decreases with the increase of quenching distance,at the same time,a low quenching area ratio is not enough to achieve the best wear resistance.However,if the quenching area ratio is too large,it will be crushed due to the large hardened area,which will increase the possibility of surface damage and peeling.In order to obtain the best comprehensive wear resistance,under the conditions of quenching power 6.5 k W,quenching time 0.7s and gas flow 5.5L/min,the spot quenching process with the quenching distance of 10 mm and the quenching area ratio of 30% is the optimized process parameter.