钢轨表面宽带激光淬火工艺及其疲劳磨损性能
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摘要
针对目前钢轨强化采用的欠速淬火方法存在强化层硬度偏低、耐磨性难以满足重载线路使用要求的问题,使用3种不同光斑宽度的激光,研究了U71Mn材质钢轨的激光淬火强化工艺,获得了不同扫描速度下的临界功率和淬火层深,并测试了淬火层在滚动接触条件下的磨损与接触疲劳性能。结果表明:在临界熔化的激光能量密度下,光斑宽度由6mm增加到20mm时,淬火层深度提高了38%,或在获得相同的淬火层深度情况下,处理效率提高6.8倍;淬火层组织为针状马氏体,硬度从原来的300HV提高到800HV以上;20万周次的磨损试验后,激光淬火试样的磨损量只有未处理试样磨损量的25%,未处理试样以表面接触疲劳剥落和塑性变形为主,激光淬火试样仅有轻微的疲劳磨损,耐磨性和抗接触疲劳性能优异。
Nowadays,online slack quenching technique was widely used for the hardening of steel rails,but the hardness of hardened layers was relatively low and was insufficient to meet the wear resistance demands of heavy-haul railways.Laser hardening process was carried out on U71 Mn rail surfaces by utilizing rectangle laser beam size with three different widths.The critical laser powers and hardened layer depths at different scanning velocities were obtained for the three different laser beam sizes.Furthermore,the wear and rolling contact fatigue property of laser-hardened layers were also investigated.Results show that under the same critical laser powers,the increase of laser beam widths from 6mm to 20 mm results in a significant increase in hardened depths(about 38%)or productivity(about 6.8times);the microstructures of the laser-hardened layers are composed of acicular martensite and have a much higher microhardness of 800 HV in comparison with that of the original steel rails(about 300HV);the weight losses of laser-hardened specimens are only 25%of the untreated ones after200 thousand cycle RCF tests;the damaged surfaces display severe contact fatigue spalling and plastic deformations for the untreated specimens but only slight fatigue wear for the laser-hardened specimens,which indicate the outstanding wear and RCF resistances for the laser-hardened rails.
Nowadays,online slack quenching technique was widely used for the hardening of steel rails,but the hardness of hardened layers was relatively low and was insufficient to meet the wear resistance demands of heavy-haul railways.Laser hardening process was carried out on U71 Mn rail surfaces by utilizing rectangle laser beam size with three different widths.The critical laser powers and hardened layer depths at different scanning velocities were obtained for the three different laser beam sizes.Furthermore,the wear and rolling contact fatigue property of laser-hardened layers were also investigated.Results show that under the same critical laser powers,the increase of laser beam widths from 6mm to 20 mm results in a significant increase in hardened depths(about 38%)or productivity(about 6.8times);the microstructures of the laser-hardened layers are composed of acicular martensite and have a much higher microhardness of 800 HV in comparison with that of the original steel rails(about 300HV);the weight losses of laser-hardened specimens are only 25%of the untreated ones after200 thousand cycle RCF tests;the damaged surfaces display severe contact fatigue spalling and plastic deformations for the untreated specimens but only slight fatigue wear for the laser-hardened specimens,which indicate the outstanding wear and RCF resistances for the laser-hardened rails.
引文
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[16] SEO J,KWON S,JUN H,et al.Fatigue Crack Growth Behavior of Surface Crack in Rails[J].Procedia Engineering,2010,2(1):865-872.
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[18] ZHONG W,HU J J,SHEN P,et al.Experimental Investigation between Rolling Contact Fatigue and Wear of High-speed and Heavy-haul Railway and Selection of Rail Material[J].Wear,2011,271(9):2485-2493.
[19] FU Z K,DING H H,WANG W J,et al.Investigation on Microstructure and Wear Characteristic of Laser Cladding Fe-based Alloy on Wheel/Rail Materials[J].Wear,2015,330/331:592-599.
[2]王文健,郭俊,刘启跃.重载钢轨磨耗损伤与预防措施研究[C]//全国青年表面工程论坛.宁波,2012:247.WANG Wenjian,GUO Jun,LIU Qiyue.Study onWear Damage Behavior of Preventive Measures of Heavy-haul Rail[C].National Youth Forum on Surface Engineering.Ningbo,2012:247.
[3]丁昊昊,王文健,郭俊,等.轴重对轮轨材料滚动磨损与损伤行为影响[J].材料工程,2015,43(10):35-41.DING Haohao,WANG Wenjian,GUO Jun,et al.Effect of Axle-load on Rolling Wear and Damage Behaviors of Wheel and Rail Materials[J].Journal of Materials Engineering,2015,43(10):35-41.
[4] ALDAJAH S H,AJAYI O O,FENSKE G R.Full Scale Friction and Durability Testing of Laser Glazed Rail[C]//STLE/ASME 2006International Joint Tribology Conference.San Antonio,2006:1109-1144.
[5] ALDAJAH S H.Effect of Laser Glazing Process on Rail Contact Fatigue Life[J].Emirates Journal for Engineering Research,2009,14(1):1-8.
[6] ALDAJAH S H,AJAYI O O,FENSKE G R.Laser Glazing Process Development and Optimization for Railroad Applications[C]//STLE/ASME 2006International Joint Tribology Conference.San Antonio,2006:1081-1107.
[7] REIFF R.In-track Demonstration of Laser-treated Rail to Reduce Friction and Wear[R].Washington:U.S.Department of Transportation,2007.
[8]曾东方,鲁连涛,李正阳,等.激光离散处理车轮钢-钢轨钢摩擦副的摩擦学性能研究[J].摩擦学学报,2014,34(1):79-86.ZENG Dongfang,LU Liantao,LI Zhengyang,et al.Tribological Properties of Laser Dispersed Treated Wheel Steel-rail Steel Tribopairs[J].Tribology,2014,34(1):79-86.
[9]曹熙,王文健,刘启跃,等.激光离散淬火对轮轨材料磨损与损伤性能的影响[J].中国表面工程,2016,29(5):72-79.CAO Xi,WANG Wenjian,LIU Qiyue,et al.Effect of Laser Dispersed Quenching on Wear and Damage Performances of Wheel/Rail Materials[J].China Surface Engineering,2016,29(5):72-79.
[10]王宝安,蔡宝春,杨兵,等.激光离散熔凝对小滑差率接触疲劳性能的影响[J].应用激光,2014,34(6):518-523.WANG Baoan,CAI Baochun,YANG Bing,et al.Effect of Laser Dispersed Melting on Contact Fatigue with Low Slip Ratio[J].Applied Laser,2014,34(6):518-523.
[11] LI Z Y,XING X H,YANG M J,et al.Investigation on Rolling Sliding Wear Behavior of Wheel Steel by Laser Dispersed Treatment[J].Wear,2014,314(1/2):236-240.
[12] LI X,ZHONG M.Research on Laser Strengthening Rail Steel and Its Wear and Friction Properties[C]//Proceedings of SPIE:the International Society for Optical Engineering.Beijing,2005:32-38.
[13] DIMELFI R J,SANDERS P G,HUNTER B,et al.Mitigation of Subsurface Crack Propagation in Railroad Rails by Laser Surface Modification 1[J].Surface&Coatings Technology,1997,106(1):30-43.
[14]孔德军,张垒,宋仁国,等.激光淬火对40CrNiMo高强度钢疲劳性能与断口形貌的影响[J].中国激光,2013,40(11):101-107.KONG Dejun,ZHANG Lei,SONG Renguo,et al.Effect of Laser Quenching on Fatigue Properties and Fracture Morphologies of 40CrNiMo High Strength Steel[J].Chinese Journal of Lasers,2013,40(11):101-107.
[15]王文健,刘启跃.车轮踏面剥离机理研究[J].机械,2004,31(6):12-15.WANG Wenjian,LIU Qiyue.Research Review on Wheel Tread Spalling[J].Machinery,2004,31(6):12-15.
[16] SEO J,KWON S,JUN H,et al.Fatigue Crack Growth Behavior of Surface Crack in Rails[J].Procedia Engineering,2010,2(1):865-872.
[17]王彩芸.钢轨磨损特性实验研究与数值分析[D].成都:西南交通大学,2013.WANG Caiyun.Experimental and Numerical Study on Rail Wear Characteristic[D].Chengdu:Southwest Jiaotong University,2013.
[18] ZHONG W,HU J J,SHEN P,et al.Experimental Investigation between Rolling Contact Fatigue and Wear of High-speed and Heavy-haul Railway and Selection of Rail Material[J].Wear,2011,271(9):2485-2493.
[19] FU Z K,DING H H,WANG W J,et al.Investigation on Microstructure and Wear Characteristic of Laser Cladding Fe-based Alloy on Wheel/Rail Materials[J].Wear,2015,330/331:592-599.