Rolling Contact Fatigue and Sliding Wear Performance of Ferritic Nitrocarburized M-50 Steel

The rolling contact fatigue and sliding wear performance of two types of ferritic nitrocarburizing techniques (gaseous and fluidized bed) were evaluated on AISI M-50 steel. These processes produced a thin compound layer over a nitrogen-rich diffusion zone. It was observed that compound layer thicknesses less than 1 μm increased the rolling contact fatigue (RCF) L₁₀ life up to a factor of six over the untreated M-50 steel. Compound layers greater than 2 μm had a tendency to flake off the substrate near the spalled region, producing lower L₁₀ lives than the baseline M-50 steel. Sliding wear tests on ferritic nitrocarburized M-50 showed that the compound layer exhibited slightly larger friction coefficients than the nitrogen-rich diffusion zone, although this layer had slightly greater resistance to catastrophic wear at higher contact stresses.     

Rolling Contact Fatigue Performance of Vibro-Mechanical Textured Surfaces

The rolling contact fatigue (RCF) performance of vibro-mechanical textured surfaces in a point elastohydrodynamic lubrication (EHL) condition is investigated. Two dimple designs, small (100 μ m × 100 μ m) and large (240 μ m × 100 μ m), are compared with a nontextured sample. Experimental RCF tests show that the textured surfaces exhibit a significantly reduced number of cycles to failure compared with the nontextured sample for the high load, pure rolling conditions evaluated. In order to understand these results, numerical models are used to calculate the lubrication and contact pressure conditions and the subsurface stress distribution. The fatigue failure trends observed experimentally are compared with the simulation results with good agreement. It is determined that RCF performance is related to the presence and size of the generated dimple.     

Influence of Initial Residual Stress on Material Properties of Bearing Steel During Rolling Contact Fatigue

Rolling contact fatigue (RCF) experiments were performed on AISI M50 bearing balls using a single ball test rig to investigate the evolution of the material properties within the RCF-affected subsurface region. Using a combination of micro-indentation and miniature compression testing methods, the influence of contact stress, initial residual stresses, and the number of contact cycles on the resulting evolution of material properties was investigated. It was found that the balls with initial residual compressive stresses show less change in material properties after RCF loading than the balls without such initial residual stresses. The formation of a light etching region (LER) is shown to not correlate with a decrease in material strength and hardness, but it does serve as a predictor for failure due to spall.     

高碳贝氏体轴承钢滚动接触疲劳性能的研究

以GCr15Si1Mo贝氏体轴承钢为研究对象,在油润滑条件和无润滑条件下,对不同初始碳化物体积分数的试样进行滚动接触疲劳试验,采用扫描电镜观察试验前后试样的表面形貌和碳化物分布,并通过Weibull曲线确定试样滚动接触疲劳性能的优劣性。结果表明,在无润滑条件下,碳化物体积分数为1.9%的试样滚动接触疲劳性能优于碳化物体积分数为5.1%的试样。在油润滑条件下,贝氏体轴承钢的滚动接触疲劳性能的优劣性依次为：无初始碳化物试样、碳化物体积分数为5.1%试样、碳化物体积分数为1.9%试样。碳化物作为基体的硬质相,很容易成为疲劳源,无初始碳化物的贝氏体轴承钢的滚动接触疲劳性能优于有碳化物的贝氏体轴承钢;碳化物脱落后的凹坑增大了润滑油和试样表面的粘着力,有利于增加油膜厚度,从而提高滚动接触疲劳寿命。     

润滑油添加剂对轴承钢球滚动接触疲劳寿命的影响

利用自制的球—棒疲劳试验机研究了4种添加剂对GCrl5钢球接触疲劳性能的影响，并借助于扫描电镜分析了不同添加剂对钢球接触疲劳的作用机理。结果表明，4种添加剂都不同程度地提高了GCrl5钢球的接触疲劳寿命，其中以含磷的极压添加剂T305和含有活性基团的降凝剂仍旧效果为佳。     

氮化硅陶瓷球显微结构与滚动接触疲劳性能

利用扫描电子显微技术分析了4种氮化硅陶瓷球的显微结构，用新研制的三点接触纯滚动加速疲劳试验机，试验研究了4种陶瓷球的接触疲劳性能，并对疲劳球表面进行了显微观察。研究表明，相同试验工况下，不同的显微结构，其韧性、强度、寿命和温升明显不同。细小致密的等轴状晶粒、玻璃相少的陶瓷球的滚动接触疲劳性能优于长针状晶粒、玻璃相多的陶瓷球。     

Some Effects of Additives on Rolling Contact Fatigue

To study the influence of lubricant physical and chemical properties on rolling contact fatigue, a variety of base stocks and additives were evaluated with a 4-ball type fatigue machine. The effect of viscosity was found to depend on the means by which a given viscosity was achieved. Although some commonly used EP and antiwear additives had a pronounced effect on fatigue life, the direction and magnitude of the additive effect depended on the particular additive and its concentration in the blend. In addition, it was observed that the additive effect depended on the choice of base oil and ball steel. These results indicate that the chemical properties as well as the physical properties of the lubricant, can be important in rolling contact fatigue.     

轧制压下率对碳钢/不锈钢复合板界面结合性能的影响

采用非真空轧制非对称组坯方式在不同总压下率(28％～70％)下制备Q235碳钢/304不锈钢复合板,研究了复合板界面处的组织、夹杂物形貌、硬度和剪切强度,探讨了界面夹杂物与脱碳层对界面结合强度的竞争性影响.结果表明:随着轧制总压下率的增加,复合板界面夹杂物由集中分布的块状变为均匀分布的颗粒状;当轧制总压下率由28％增大到47％时,影响复合板界面结合强度的主要因素是界面夹杂物,增加轧制压下率有利于提高界面结合强度;当轧制总压下率由47％增大到70％时,不锈钢侧晶粒尺寸急剧减小,碳钢侧脱碳层厚度增加,界面结合强度降低,脱碳层成为影响结合强度的主导因素.可以通过合理控制轧制压下率来平衡界面夹杂物和脱碳层对结合强度的竞争性影响.     

滚动接触疲劳试验机的研究现状

滚动接触疲劳试验机主要用于研究材料在模拟工况条件下的接触疲劳性能。本文就国内外已经实际应用的滚动接触疲劳试验机的现状及接触疲劳试验基本工作原理加以介绍,并就滚动接触疲劳试验机的发展方向作了探讨。     

钢轨滚动接触疲劳研究

介绍了滚动接触疲劳裂纹的萌生及扩展的形成机理、钢轨滚动接触疲劳的破坏分类、影响因素,从钢轨新材料的开发、轮轨接触几何型面的优化和铁路工况的改善等几个方面提出了减缓钢轨滚动接触疲劳的措施。     

Crack Propagation of Rolling Contact Fatigue in Ball Bearing Steel Due to Tensile Strain

Crack propagations or failure modes in rolling element bearings, which had been difficult to explain via conventional crack propagation mechanisms such as the orthogonal shear stress mechanism, were discussed from the viewpoint of a tensile strain mechanism. Contact stresses are compressive in three axes, whose values differ from each other; then strain can be tensile in one of these directions, acting at a right angle to the direction of maximum compressive stress. A crack is considered to propagate by this tensile strain. When contact stress is small, a crack produced by some cause can propagate by this elastic tensile strain. When contact stress is large, residual tensile strain is produced by plastic deformation, which can also influence the crack propagation. Several failure modes of rolling element bearings, which had been difficult to explain, were explained by tensile strain.     

Cr4Mo4V钢滚道表面缺陷对接触疲劳寿命的影响

通过对预制出缺陷的Cr4Mo4V钢制推力片试样进行接触疲劳寿命的测试,研究轴承滚道面存在的缺陷对其寿命的影响。结果表明,滚道上存在的表面缺陷会显著缩短其使用寿命,并且发现,在缺陷处的疲劳剥落大都发生在滚动体运行的出口边附近。     

An Electron Microscope Study of Rolling Contact Fatigue

Progressive changes in the surface topography of the running track in a rolling contact fatigue tester were studied by using replica techniques and the electron microscope. Early in the life of a specimen, micron she cracks appeared on the stressed surface. With further running more cracks appeared, but those existing did not grow to any extent except for isolated cases. When the lubricant was changed, the time to form the first few cracks and the rate of formation of additional cracks correlated well with the fatigue performance.

Etching of the ball tracks showed that the surface cracks observed were almost always located at the chrome carbide to martensite interface.

It is postulated that corrosion fatigue may contribute to the differences between the fatigue performance of lubricants as much or more so than elastohydrodynamic effects.     

水润滑条件下转速对车轮钢滚动接触疲劳和磨损性能的影响

为探究水润滑条件下转速对车轮钢滚动接触疲劳和磨损性能的影响,利用滚动接触摩擦磨损试验测试不同转速下车轮试样的剥离寿命、摩擦因数和磨损率,并结合磨损形貌和裂纹扩展形貌观察,对比分析不同转速下摩擦磨损和剥离寿命的影响因素。结果表明:随转速提高,车轮材料氧化程度加剧,导致摩擦因数逐渐增加;当转速由250 r/min增至500 r/min时,摩擦因数增幅较小,应变速率增加导致磨损率下降,当转速由500 r/min增至1000 r/min时,摩擦因数急剧增加,导致材料磨损率增加;随转速提高,剖面塑性流动层厚度、裂纹扩展角度、裂纹分叉深度和最大扩展深度均呈现减小趋势。转速增加带来的摩擦因数的增加,一方面缩短裂纹萌生寿命,另一方面减小了裂纹发生向上转折的深度,最终导致滚动接触疲劳寿命随转速的增加而减小。     

弯矩作用下钢轨滚动疲劳裂纹扩展行为研究

在JD-1轮轨模拟试验机上,通过设计模拟小轮的结构,对钢轨试样在弯矩作用下的裂纹扩展行为进行研究.试验结果表明:裂纹一般在应力集中处萌生,当裂纹扩展到一定程度后容易产生变向甚至分叉;在其他参数相同的情况下,预制裂纹尺寸对疲劳裂纹扩展有较大影响,预制裂纹较宽时裂纹扩展速率明显加快.     

A Review of Microstructural Alterations around Nonmetallic Inclusions in Bearing Steel during Rolling Contact Fatigue

Microstructural alterations in bearing steels during rolling contact cycling have been reported in the literature for more than 60 years. These changes appear in different shapes and locations. One class of such alterations is “butterfly wings”: regions of microstructurally transitioned material that appear diagonally around nonmetallic inclusions and may serve as fatigue crack initiation sites. Over the course of the past half a century numerous experimental and multiple analytical efforts have been made to understand and model this phenomenon, yet a lot is to be discovered and understood about root causes and mechanisms leading to butterfly formation. This article presents a comprehensive overview of the crack nucleation phenomena due to butterfly formation, its characteristics, and its negative impact on bearing service life. Significant attempts that have been made to solve the problem over the past half a century are mentioned, with a focus on recent work. Unanswered dilemmas are particularly discussed to highlight avenues of future research.     

Lubricant Chemistry in Rolling Contact Fatigue—The Performance and Mechanism of One Antifatigue Additive

The paper describes studies towards developing lubricant additive technology to improve the fatigue performance of an oil. The extraordinary performance of a particular organic phosphonate antifatigue additive observed in the authors' laboratory and elsewhere is reviewed together with conflicting EHD film thickness studies of this additive reported in the literature. New optical EHD measurements and electron microscope and microprobe studies which define the mechanism by which the additive acts, are presented.     

近疲劳强度载荷下WC/Co涂层对300M钢疲劳性能的影响

研究了在近疲劳强度载荷下超音速火焰喷涂WC/Co涂层和电镀铬层对300 M低合金钢疲劳性能的影响.结果表明：WC/Co涂层、电镀铬层试样和300 M钢基体的疲劳强度分别为753,600和720 MPa.在近疲劳强度载荷下,WC/Co涂层试样的疲劳寿命分别为基体和电镀铬层试样的1.5～2和5～10倍.三者的主裂纹源均为基体内部的Al2O3和SiO2夹杂物.电镀铬层中的次裂纹穿过界面并向基体中扩展,在基体表面形成新的次裂纹源,加快了基体中主裂纹源的形成和主裂纹的扩展;而WC/Co涂层中的次裂纹经过界面时向界面方向偏转,形成无支撑涂层,并最终使涂层剥落.     

不同润湿性微/纳织构化刀具切削性能研究

针对15-5PH固溶处理不锈钢等难加工材料切削过程中刀具磨损快速的问题,采用激光加工及表面处理技术制备得到不同润湿性的硬质合金微/纳织构化刀具。通过对15-5PH固溶处理不锈钢的切削试验,研究了不同润湿性微/纳织构化刀具的切削性能及减摩机理。试验结果表明:在微量润滑条件下,刀具表面低润湿性微/纳织构的存在可有效降低切削力、前刀面平均摩擦系数及切削温度,同时还能进一步改善刀—屑界面的润滑状况,减缓刀具磨损。     

Influence of Different Application of Lubricants on Wear and Pre-existing Rolling Contact Fatigue Cracks of Rail Materials

Rolling contact fatigue (RCF) of rail can be a significant problem affecting safety and maintenance. Rail materials have been optimized to reduce it, but not enough is known about how friction management products applied to the rail affect crack growth. This study presents experimental results carried out to explore the influence of different lubricants and application orders on wear and pre-existing RCF cracks in rail materials. The results indicate that the types or properties of lubricants have a vital role in the wear rate and fatigue crack growth characteristics of rail materials after conditioning with 5000 dry cycles to initiate cracks. Using a different application order of two lubricants has a significant influence on the crack growth angles in the rail rollers.