M50 steel,commonly utilized in aircraft engine bearings,is susceptible to friction-induced failures,particularly in high-temperature service conditions.To address this issue,various strategies have been proposed,with ...M50 steel,commonly utilized in aircraft engine bearings,is susceptible to friction-induced failures,particularly in high-temperature service conditions.To address this issue,various strategies have been proposed,with laser shock peening(LSP)garnering significant attention due to its deeper residual stress penetration and excellent surface integrity,whereas the underlying strengthening mechanisms have not yet been fully elucidated.In this study,we systematically investigate the impact of LSP treatment on the tribological properties of M50 steel at temperatures of 25 and 300℃,alongside elucidating the relevant micro-mechanisms.Microstructural analysis reveals that laser impact strengthening primarily arises from dislocation proliferation,resulting in a surface hardness increase of approximately 14%and the formation of a substantial compressive stress layer reaching a maximum value of about 1200 MPa,with a depth of around 2 mm.Friction test results demonstrate reduced coefficients of friction and wear rates following LSP treatment at both temperatures.Notably,a more pronounced reduction is observed at 300℃,with values decreasing by 41.4%and 55.8%,respectively.The enhanced performance is attributed to the synergistic interplay of compressive residual stresses,work-hardening layers,increased density of dislocations,and substantial microstructure refinement.展开更多
【目的】M50钢作为当前主流的航发轴承套圈材料,在淬回火处理前往往对其进行冷环轧处理以实现套圈的成形。然而,M50常温下变形抗力较大,传统冷环轧工艺在大变形量下极易产生微纳损伤,影响其晶粒细化程度,进而限制了其在淬回火过程中的...【目的】M50钢作为当前主流的航发轴承套圈材料,在淬回火处理前往往对其进行冷环轧处理以实现套圈的成形。然而,M50常温下变形抗力较大,传统冷环轧工艺在大变形量下极易产生微纳损伤,影响其晶粒细化程度,进而限制了其在淬回火过程中的微观组织遗传效果,导致其力学性能提升有限。因此,提出了一种在相同冷环轧参数下通过电脉冲辅助进一步提升M50钢的晶粒细化程度的方法,进而提升M50钢在淬回火过程中的微观组织遗传效果。【方法】采取电脉冲辅助M50冷环轧-淬回火(Electric Pulse-assisted Cold Ring Rolling-Quenching and Tempering,EPCRR-QT)处理,通过在冷环轧过程中对M50钢同步施加脉冲电流,进一步优化了微观组织,并分析了其在淬回火处理时的微观组织演变规律。【结果】结果表明,相较于传统冷环轧-淬回火试样,电脉冲辅助M50冷环轧-淬回火试样的原奥氏体晶粒尺寸细化了15.2%,残余奥氏体含量、碳化物Mo2C含量、小角度晶界占比同样有所降低,淬火态、回火态的维氏硬度分别提升了4.7%、4.4%。展开更多
M50轴承钢中主要的碳化物类型为MC、M_(2)C和M_(23)C_(6)。扫描电子显微镜(Scanning Electron Microscopy,SEM)下,3种碳化物的形状、尺寸和在材料中的分布存在明显的区别。有些碳化物的尺寸较大且分布不均匀。轴承受载过程中,这些碳化...M50轴承钢中主要的碳化物类型为MC、M_(2)C和M_(23)C_(6)。扫描电子显微镜(Scanning Electron Microscopy,SEM)下,3种碳化物的形状、尺寸和在材料中的分布存在明显的区别。有些碳化物的尺寸较大且分布不均匀。轴承受载过程中,这些碳化物会成为应力集中的区域,对轴承疲劳性能产生负面影响。为了高效地获得材料中的碳化物信息,提出一种改进的掩膜基于区域的卷积神经网络(Mask Region-based Convolutional Neural Network,Mask R-CNN)模型,可批量鉴别SEM图像中3种碳化物的种类,确定其尺寸大小及分布。网络模型输出的图像和数值结果显示,M50轴承钢中M_(2)C型碳化物尺寸大且分布不均匀,但总体尺寸最大的MC型碳化物和尺寸最小的M_(23)C_(6)型碳化物分布相对均匀。展开更多
Electroshocking treatment(EST),an efficient and rapid material treatment method,promotes microstructure evolution and improves mechanical properties.This study incorporates EST into the conventional cold rolling-quenc...Electroshocking treatment(EST),an efficient and rapid material treatment method,promotes microstructure evolution and improves mechanical properties.This study incorporates EST into the conventional cold rolling-quenching tempering process of M50 steel and investigates the influence and mechanism of applying EST at different stages of the process on the microstructure and mechanical properties.Scanning electron microscope(SEM),transmission electron microscope(TEM),and X-ray diffraction(XRD)were used to characterize the effect of EST on microstructure.The results show that EST can refine the grains of M50(average reduction of 10.1%in grain size),homogenize the grain size distribution,reduce the dislocation density(20.9%in average),promote the dissolution of carbides in the matrix and distribute them more uniformly along the grain boundaries,resulting in the improvement of mechanical properties.The mechanical properties of the specimen with the process flow of rolling-quenching-tempering-electroshocking showed excellent performance,with an increase in hardness of 1.4%,tensile strength of 17.7%,and elongation at break of 24.3%as compared to the specimen without EST.The tensile properties of the specimen with the process flow of rolling electroshocking-quenching-tempering showed the best performance,with an increase in tensile strength of 30.0%and elongation at break of 30.7%as compared to the specimen without EST.展开更多
The use of an alternative magnetic field during vacuum arc remelting(VAR)can have significant effects on the primary carbide and mechanical properties of M50-bearing steel.The solidification structure and the primary ...The use of an alternative magnetic field during vacuum arc remelting(VAR)can have significant effects on the primary carbide and mechanical properties of M50-bearing steel.The solidification structure and the primary carbide morphology of the VAR ingot were analyzed by optical microscopy and scanning electron microscopy.Characterization and analysis of the growth direction of primary carbides were conducted using high-resolution rapid electron backscatter diffraction.Solute elements segregation was analyzed using an electron probe microanalyzer.FLUENT was utilized to conduct numerical simulations to validate the experimental findings and elucidate the underlying mechanism.Compared to traditional VAR,magnetic-controlled VAR generates a horizontal circulation,which makes a shallower and flatter molten pool and a more even temperature distribution.In the time dimension,the local solidification time is shortened,and the concentration of solute elements will be alleviated.In the spatial dimension,the secondary dendrite arm spacing decreases,alleviating the degree of inter-dendritic segregation.Consequently,the possibility of forming a segregation diminishes.Both aspects promote the even distribution of solute atoms,resulting in less segregation and hindering the development of primary carbide.This leads to the refinement of primary carbide size and its uniform distribution.The magnetic-controlled vacuum arc melting not only refines the dendritic structure in the M50 ingot,causing it to expand more axially along the ingot,but also refines primary carbides and improves tensile and wear-resistant mechanical properties.展开更多
基金supported by the National Science and Technology Major Project of China(No.2017-VII-0003-0096)the National Natural Science Foundation of China(Grant Nos.52205240 and 52201140)+2 种基金the Young Elite Scientist Sponsorship Program by CAST(Grant No.YESS20200321)the Natural Science Foundation for Youths of Shaanxi Province(No.2023-JC-QN-0521)the China Postdoctoral Science Foundation(Grant No.2022M723874).
文摘M50 steel,commonly utilized in aircraft engine bearings,is susceptible to friction-induced failures,particularly in high-temperature service conditions.To address this issue,various strategies have been proposed,with laser shock peening(LSP)garnering significant attention due to its deeper residual stress penetration and excellent surface integrity,whereas the underlying strengthening mechanisms have not yet been fully elucidated.In this study,we systematically investigate the impact of LSP treatment on the tribological properties of M50 steel at temperatures of 25 and 300℃,alongside elucidating the relevant micro-mechanisms.Microstructural analysis reveals that laser impact strengthening primarily arises from dislocation proliferation,resulting in a surface hardness increase of approximately 14%and the formation of a substantial compressive stress layer reaching a maximum value of about 1200 MPa,with a depth of around 2 mm.Friction test results demonstrate reduced coefficients of friction and wear rates following LSP treatment at both temperatures.Notably,a more pronounced reduction is observed at 300℃,with values decreasing by 41.4%and 55.8%,respectively.The enhanced performance is attributed to the synergistic interplay of compressive residual stresses,work-hardening layers,increased density of dislocations,and substantial microstructure refinement.
文摘【目的】M50钢作为当前主流的航发轴承套圈材料,在淬回火处理前往往对其进行冷环轧处理以实现套圈的成形。然而,M50常温下变形抗力较大,传统冷环轧工艺在大变形量下极易产生微纳损伤,影响其晶粒细化程度,进而限制了其在淬回火过程中的微观组织遗传效果,导致其力学性能提升有限。因此,提出了一种在相同冷环轧参数下通过电脉冲辅助进一步提升M50钢的晶粒细化程度的方法,进而提升M50钢在淬回火过程中的微观组织遗传效果。【方法】采取电脉冲辅助M50冷环轧-淬回火(Electric Pulse-assisted Cold Ring Rolling-Quenching and Tempering,EPCRR-QT)处理,通过在冷环轧过程中对M50钢同步施加脉冲电流,进一步优化了微观组织,并分析了其在淬回火处理时的微观组织演变规律。【结果】结果表明,相较于传统冷环轧-淬回火试样,电脉冲辅助M50冷环轧-淬回火试样的原奥氏体晶粒尺寸细化了15.2%,残余奥氏体含量、碳化物Mo2C含量、小角度晶界占比同样有所降低,淬火态、回火态的维氏硬度分别提升了4.7%、4.4%。
基金Project(G202403)supported by the Open Foundation of The State Key Laboratory of Refractories and Metallurgy,ChinaProject(2022CFB378)supported by the Natural Science Foundation of Hubei Province,China+2 种基金Project(B 17034)supported by 111 Project,ChinaProject(IRT_17R83)supported by the Innovative Research Team Development Program of Ministry of Education of ChinaProject(P2024-026)supported by the Open Foundation of The State Key Laboratory of Materials Processing and Die&Mould Technology,China。
文摘Electroshocking treatment(EST),an efficient and rapid material treatment method,promotes microstructure evolution and improves mechanical properties.This study incorporates EST into the conventional cold rolling-quenching tempering process of M50 steel and investigates the influence and mechanism of applying EST at different stages of the process on the microstructure and mechanical properties.Scanning electron microscope(SEM),transmission electron microscope(TEM),and X-ray diffraction(XRD)were used to characterize the effect of EST on microstructure.The results show that EST can refine the grains of M50(average reduction of 10.1%in grain size),homogenize the grain size distribution,reduce the dislocation density(20.9%in average),promote the dissolution of carbides in the matrix and distribute them more uniformly along the grain boundaries,resulting in the improvement of mechanical properties.The mechanical properties of the specimen with the process flow of rolling-quenching-tempering-electroshocking showed excellent performance,with an increase in hardness of 1.4%,tensile strength of 17.7%,and elongation at break of 24.3%as compared to the specimen without EST.The tensile properties of the specimen with the process flow of rolling electroshocking-quenching-tempering showed the best performance,with an increase in tensile strength of 30.0%and elongation at break of 30.7%as compared to the specimen without EST.
基金supported by the National Natural Science Foundation of China(Grant numbers 52204347,52274385,52004156,51904184,and 52204392)the National Key Research and Development Program of China(Grant number 2022YFC2904900)+1 种基金the Science and Technology Commission of Shanghai Municipality(13JC14025000,15520711000)the Shi Changxu Innovation Center for Advanced Materials(SCXKFJJ202204).
文摘The use of an alternative magnetic field during vacuum arc remelting(VAR)can have significant effects on the primary carbide and mechanical properties of M50-bearing steel.The solidification structure and the primary carbide morphology of the VAR ingot were analyzed by optical microscopy and scanning electron microscopy.Characterization and analysis of the growth direction of primary carbides were conducted using high-resolution rapid electron backscatter diffraction.Solute elements segregation was analyzed using an electron probe microanalyzer.FLUENT was utilized to conduct numerical simulations to validate the experimental findings and elucidate the underlying mechanism.Compared to traditional VAR,magnetic-controlled VAR generates a horizontal circulation,which makes a shallower and flatter molten pool and a more even temperature distribution.In the time dimension,the local solidification time is shortened,and the concentration of solute elements will be alleviated.In the spatial dimension,the secondary dendrite arm spacing decreases,alleviating the degree of inter-dendritic segregation.Consequently,the possibility of forming a segregation diminishes.Both aspects promote the even distribution of solute atoms,resulting in less segregation and hindering the development of primary carbide.This leads to the refinement of primary carbide size and its uniform distribution.The magnetic-controlled vacuum arc melting not only refines the dendritic structure in the M50 ingot,causing it to expand more axially along the ingot,but also refines primary carbides and improves tensile and wear-resistant mechanical properties.
