连铸和模铸轴承钢性能的比较

检验了连铸和模铸轴承钢棒材的低倍组织,非金属夹杂物级别,碳化物形状和分布及疲劳寿命。结果表明,模铸材的氧化物夹杂的含量、平均尺寸和最大尺寸均小于连铸材,模铸材的碳化物均匀性和接触疲劳寿命也优于连铸材,但其生产成本高于连铸材。     

残留奥氏体含量对GCr15轴承钢摩擦磨损性能的影响

首先对GCr15轴承钢进行了不同温度的淬火和回火处理及淬火+深冷+回火处理,获得了残留奥氏体含量分别为6.2、11.2、17.5和26.4 vol%的GCr15轴承钢试样,随后采用重载往复摩擦磨损实验仪在干摩擦和油润滑条件下对试样进行摩擦磨损实验,研究了残留奥氏体含量对GCr15轴承钢滑动摩擦磨损性能的影响;利用X射线衍射仪(XRD)、扫描电镜(SEM)、X射线残余应力分析仪和洛氏硬度计等分析了GCr15轴承钢试样在不同状态下的组织、表面形貌和力学性能。结果表明：经不同工艺热处理后,GCr15轴承钢的组织都是由马氏体、残留奥氏体和碳化物组成;随着残留奥氏体含量增加,GCr15轴承钢的表面硬度逐渐减小,残余压应力逐渐减小并趋于稳定;在干摩擦条件下,深冷处理试样的平均摩擦系数最小;在油润滑条件下,4组试样的平均摩擦系数相差不大且都低于0.08,在干摩擦和油润滑条件下,随着残留奥氏体含量升高,GCr15轴承钢的磨损率都是先升高再降低,在淬火温度为865℃时磨损率达到最大;经过深冷处理的试样的残留奥氏体含量最小,为6.2 vol%,其磨损率也最小,说明深冷处理能提高GCr15轴承钢的摩擦磨损性...     

深层滚压加工对高碳铬轴承钢超长寿命疲劳行为的影响

深层滚压加工对高碳铬轴承钢超长寿命疲劳行为的研究表明：与深层滚压加工前相同,在高应力幅短寿命区,疲劳裂纹萌生于试样表面;由于表面压缩残余应力的影响,疲劳强度有所提高．在低应力幅长寿命区,疲劳裂纹萌生位置从未经深层滚压加工试样的次表面向深层滚压加工试样内部没有压缩残余应力和硬化层的位置转移;因弯曲应力梯度的影响,疲劳强度有了较大的提高．深层滚压加工可以提高高碳铬轴承钢在超长寿命区的旋转弯曲疲劳强度．     

GCr15轴承钢接触疲劳次表面裂纹的跟踪观察SCIEI

本文在对轴承钢接触疲劳剥落过程进行连续追踪观测的基础上,推导了次表面裂纹扩展的估算公式。理论分析和试验结果表明,接触疲劳寿命与次表面裂纹扩展角之间存在着明显的对应关系。并对残余压应力和残余奥氏体可以提高接触疲劳寿命的原因提出了新的解释。     

回火温度对GCr15轴承钢组织和性能的影响

GCr15钢在轴承中广泛使用,其回火温度对轴承使用性能有重要影响。研究了不同回火温度对GCr15轴承钢的硬度、残余奥氏体含量、表面残余应力的影响。结果表明：当GCr15的回火温度为165~300℃时,随着回火温度的升高,硬度HRC由61.7降到56.2,残余奥氏体含量由9.88%下降到3.26%,表面残余应力由706.8 MPa下降至382.2 MPa;其显微组织主要为针状马氏体、颗粒碳化物和少量的亚稳定相残余奥氏体,随着回火温度的提高,碳化物逐渐聚集并不断长大。该研究为GCr15钢低温回火工艺的制定提供参考。     

国产与进口轴承钢组织结构与性能分析

用光镜、扫描电镜和X射线衍射仪对比分析了国产轴承钢与进口轴承钢的马氏体含量与尺寸、残余奥氏体含量、碳化物含量与尺寸以及尺寸分布情况,并测定各试样的力学性能.找出进口轴承钢性能优异的原因和国产轴承钢的不足,并对国产轴承钢提出了改进建议.结果表明,进口轴承对轴柱与轴套马氏体数量分别控制在不同范围,与国产轴承钢相比,进口轴承中碳化物细小、分布均匀,残余奥氏体含量低,有些甚至完全消除残余奥氏体.进口轴承耐磨性能优于国产轴承.     

改善轴承钢接触疲劳寿命的冶炼工艺技术进展

本文主要评述国外依托冶炼技术进步来进一步提高轴承零件的接触疲劳寿命。     

轴承钢残留奥氏体含量的测定方法及其应用

将测量相转变的"比容差法"应用至轴承钢材料的残留奥氏体含量的精确测定。由轴承钢体积定量的测量,以标准的X射线衍射法进行校验,建立了轴承钢残留奥氏体含量-比容的关系线,由此根据比容差法来定量测量残留奥氏体相的含量。对GCr15轴承钢的测量实例表明:该方法可对轴承钢冷处理后的奥氏体转变量进行精确测量,建立的工作曲线表明,GCr15钢的残留奥氏体含量与比容之间可用线性关系表示。与X射线衍射法校验的测量结果相比较,两测量结果的偏差小于8%。     

Role of the cyclic stability of retained austenite in fatigue performance of carburized 14NiCr11 steel

The role of retained austenite in the fatigue strength of carburized 14NiCr11 steel was studied by considering two gas-carburizing treatments leading to two maximum retained austenite fractions of 20 and 40%. These states led to endurance limit improvements evaluated at 40 and 10%, respectively, compared with the untreated state. These improvements were explained by the evolution of retained austenite during the cyclic loading using the dispersive x-ray diffraction technique. This reveals that the best fatigue strength is attributed to the homogeneous transformation of the retained austenite fraction in the treated layer during the cyclic loading.     

奥氏体化过程对Cr14Mo4V高温轴承钢微观组织的影响

针对高温轴承钢Cr14Mo4V开展了微观组织随奥氏体化参数演化规律研究。利用OM、XRD、SEM及硬度测试对Cr14Mo4V钢中碳化物、残留奥氏体、晶粒尺寸及硬度等进行了分析。结果表明,淬火态Cr14Mo4V高温轴承钢微观组织主要包括淬火马氏体、残留奥氏体和带状碳化物;奥氏体化过程中微观组织演化对奥氏体化温度较为敏感,随着奥氏体化温度的升高,残留奥氏体含量逐渐增加,晶粒尺寸逐渐增大,碳化物逐渐溶解,带状碳化物合金元素分布发生变化。Cr14Mo4V轴承钢硬度随奥氏体化温度的升高呈先略微增加后显著降低的趋势,主要受基体固溶度、残留奥氏体含量及晶粒尺寸等因素综合影响。     

TRACKING OBSERVATION ON SUBSURFACE CRACK IN BEARING STEEL GCr15 UNDER ROLLING CONTACT

Based on the sequent tracking observation on spalling of steel GCr15 under rolling contact fa-tigue,an expression for estimating the propagation of subsurface cracks was derived.The rol-ling contact fatigue life was found to be markedly related to the subsurface crack propagationangle.A new explanation of reason why the rolling contact fatigue life can be prolonged byresidual compressive stress and retained austenite was advanced.     

航空轴承钢的真空低压渗碳工艺

利用洛氏硬度计、维氏硬度计及光学显微镜等研究了真空低压渗碳工艺对航空轴承钢组织和性能的影响。结果表明:试验钢经渗碳后产生了大量连续的粗大网状碳化物,但在渗碳后热处理工艺中碳化物形貌逐渐变为非连续的网状;有效硬化层由渗碳后的0.45 mm逐步增加到设定值附近(0.77 mm);渗层硬度梯度中的“低头”现象也逐步消除,从渗层到心部硬度平缓降低;相较于原始硬度,试验钢的表面硬度经渗碳后增加了11 HRC,经过全工序真空低压渗碳后提高了16~18 HRC。     

航空发动机轴承钢高温碳氮共渗的渗层组织与性能

航空发动机轴承用Ｍ５０ＮｉＬ钢高温（９００～９２０℃）碳氮共渗,可获得均匀细小的淬火、回火组织,其疲劳裂纹扩展抗力和高温硬度显著高于Ｍ５０钢。分析认为,疲劳裂纹沿渗层的扩展行为与残余奥氏体的诱发裂纹闭合效应,残余压应力,以及渗层塑性、韧性对断裂机制的影响有关;渗层高温硬度的提高则是马氏体回火相析出发生改变的结果。     

GCr15钢轴承残留奥氏体、尺寸精度及疲劳寿命试验研究

对7205C/P5精密轴承和7205C/P4超精密轴承进行了工艺试验,并对不同的轴承热处理工艺,其残留奥氏体含量对尺寸精度稳定性及轴承疲劳寿命的影响进行试验研究,提出了GCr15钢制超精密轴承残留奥氏体的控制量.     

Microstructure and rolling contact fatigue life of austenitic nitrocarburized STB 2 high carbon chromium bearing steel

Microstructures and rolling contact fatigue properties of STB 2 high carbon chromium bearing steel were investigated by means of electron microscopy, hardness tests and rolling contact fatigue tests. In order to examine the influence of the heat treatment process on microstructures and rolling contact fatigue, two kinds of heat treatment processes, quenching/tempering (QT) and austenitic nitrocarburizing were performed on STB 2 steel. Rolling contact fatigue life of the nitrocarburized steel was 3.7 times longer than that of the QT treated steel under a clean lubrication condition and was 1.5 times longer under a contaminated lubrication condition. The amount of retained austenite in the nitrocarburized steel was found to be larger than that in the QT treated steel. As the tempering temperature was increased from 150°C to 300°C, the decrease in hardness for the nitrocarburized steel was smaller than that of the QT treated steel. This means that the nitrocarburized steel is suitable as bearing material for high temperature applications. Very fine Fe₄(Fe(CN)₆)₃ carbonitride of less than l00nm in diameter was found in the nitrocarburized steel. An improvement in rolling contact fatigue life in the nitrocarburized steel was attributed to the combination of the formation of very fine Fe₄(Fe(CN)₆)₃ and retained austenite.     

EFFECT OF MICROSTRUCTURE ON CORROSION FATIGUE BEHAVIOUR OF A LOW CARBON BAINITE STEEL

The behaviour towards corrosion fatigue of low carbon bainite steel with variousmicrostructures after tempered at different temperatures has been examined. The susceptibilityof the steel to corrosion fatigue may be improved by tempering at 300℃.