超硬涂层材料滚动接触疲劳试验机的研制

在总结分析目前国内外表面超硬涂层零件接触疲劳失效行为评估技术的基础上，依据超硬涂层零件接触疲劳失效机制模型，自主研制了一种超硬涂层材料滚动接触疲劳试验机。介绍了该试验机的设计原理和特殊功能，采用该试验机对51306纳米超硬材料涂层轴承滚动接触疲劳失效行为进行了试验评定。试验证明所研制的超硬涂层材料滚动接触疲劳试验机智能检测控制系统能够动态探测诊断涂层轴承表面初始疲劳裂纹并实现急停，可捕捉试验轴承表面疲劳初始状态，为超硬涂层零件接触疲劳失效机制分析提供可靠的试验依据。     

超硬涂层零件滚动接触疲劳加速实验方法研究

提出了一种新的加速超硬涂层零件滚动接触疲劳失效的实验方法,并给出了机制模型及机制分析;采用该方法,在超硬涂层材料滚动接触疲劳实验机上,对纳米超硬材料涂层轴承滚动接触疲劳失效行为开展了加速疲劳实验和常规疲劳实验的对比实验研究。实验结果表明:该方法能取得与常规疲劳实验方法疲劳行为相同的实验结果;加速疲劳实验加速比约为3,加速疲劳实验方法十分有效地节省了疲劳实验中消耗的时间。该方法是一个适应于评价超硬涂层零件滚动接触疲劳性能及研究其失效机制的新方法。     

氮化硅轴承球滚动接触疲劳性能的研究现状

对氮化硅轴承球滚动接触疲劳的研究进行了综述,介绍了影响氮化硅轴承球滚动接触疲劳性能的主要因素,包括气孔、表面微裂纹、表面强度、残余应力、表面粗糙度和润滑条件等,以及介绍了疲劳剥落失效产生的机制,分析了目前研究所存在的问题,并对今后的发展方向进行了展望。     

钢铁用耐水（WTF）轴承的开发

分析了过去的试验数据和实际使用中失效的轴承,并提出了再现渗水润滑条件下轴承疲劳寿命的试验方法,从而能够清楚地观察到轴承的剥落过程,并进一步研究材料参数对轴承寿命的影响。结果表明:渗水润滑条件下轴承失效起源于滚动接触表面的非金属夹杂物。疲劳裂纹的扩展最初是在晶界之间,然后穿晶,最终导致剥落。介绍了NSK开发的轧机用耐水(WTF)轴承。在渗水润滑条件下,它的寿命大约是传统轴承的3倍。     

钢铁用耐水(WTF(R))轴承的开发

分析了过去的试验数据和实际使用中失效的轴承,并提出了再现渗水润滑条件下轴承疲劳寿命的试验方法,从而能够清楚地观察到轴承的剥落过程,并进一步研究材料参数对轴承寿命的影响.结果表明:渗水润滑条件下轴承失效起源于滚动接触表面的非金属夹杂物.疲劳裂纹的扩展最初是在晶界之间,然后穿晶,最终导致剥落.介绍了NSK开发的轧机用耐水(WTF(R))轴承.在渗水润滑条件下,它的寿命大约是传统轴承的3倍.     

钢铁用耐水(WTF®)轴承的开发

分析了过去的试验数据和实际使用中失效的轴承,并提出了再现渗水润滑条件下轴承疲劳寿命的试验方法,从而能够清楚地观察到轴承的剥落过程,并进一步研究材料参数对轴承寿命的影响.结果表明渗水润滑条件下轴承失效起源于滚动接触表面的非金属夹杂物.疲劳裂纹的扩展最初是在晶界之间,然后穿晶,最终导致剥落.介绍了NSK开发的轧机用耐水(WTF(R))轴承.在渗水润滑条件下,它的寿命大约是传统轴承的3倍.     

热喷涂层滚动接触疲劳寿命演变规律研究进展

滚动接触疲劳寿命是评价热喷涂层性能的重要指标之一。目前,用于热喷涂层滚动接触疲劳寿命演变规律的研究方法主要可以分为三大类:理论模型法、疲劳试验法和有限元分析法。模型预测法侧重对失效机理的描述,主要通过理论推导建立模型公式,再通过试验获取模型所需参数,从而达到预测涂层寿命的目的。疲劳试验法侧重对疲劳数据的分析,通过疲劳试验机得到寿命数据,采用Weibull分布等统计模型对数据进行分析,建立不同寿命影响因素与涂层疲劳寿命之间的关系。有限元分析方法则是通过采用计算机软件模拟涂层实际工况的方法,对涂层工作中的部分参量进行科学估计,是上述两种方法的补充。从热喷涂层滚动疲劳寿命研究方法的角度出发,总结各种研究方法的研究成果,系统综述国内外学者对热喷涂层滚动接触疲劳寿命演变规律的研究现状,确定疲劳试验与有限元分析相结合的方法。     

CVD多层复合涂层的研制与应用

T_iC、T_1N、T_iCN等陶瓷涂层,摩擦系数低,超硬,耐磨耐蚀性很好。但单相涂层难以满足高的硬度和良好的韧性、涂层与基体高的界面强度和表面反应性弱等综合性能。所以CVD技术已由单相涂层向多相复合涂层发展.介绍CVD 7层复合涂层的研制,对涂层的组织结构和摩擦学性能进行了观测与对比试验。结果表明,7层复合涂层比单相涂层的相对耐磨性提高1.244倍;滚动接触疲劳的额定寿命提高了4倍。应用证明,硬质合金和高碳高合金钢工模具经CVD沉积多层复合涂层,使用寿命提高3～110倍,尤其是提高模具的抗粘着磨损能力,有效地改善了成品的表面粗糙度。CVD多层复合涂层显著提高了9Cr18不锈轴承钢的滚动接触疲劳寿命,     

基于多失效模式的轴承滚动体可靠性模型

基于轴承滚动体接触疲劳寿命概率分布服从Weibull分布和Miner累积损伤理论的失效依据，提出滚动体接触疲劳累积损伤的可靠性预测模型；同时以滚动体心部应力为失效依据，导出滚动体可靠性模型，综合考虑滚动体多失效情况，提出一种新的基于多失效模式的轴承滚动体可靠性模型。最后用实例说明了应用该模型预测轴承滚动体可靠度的方法。     

固体润滑滚子轴承的接触表面应力分析研究

为获得固体润滑滚动轴承滚动体与滚道处的接触应力,通过固体润滑滚子轴承拟动力学分析并考虑涂层的影响,获得了滚子轴承稳定运行过程中滚动体的力载分布。通过建立带涂层接触的平面应变问题的力学模型,将涂层与基底两种材料的特性等效为一种材料来求解滚子与接滚道触应力分布情况,并与轴承的拟动力学分析相结合,获得了滚子轴承中滚动体与固体润滑膜接触表面的接触变形、接触半径与外加载荷之间的关系,讨论了不同涂层的弹性模量以及不同涂层厚度对接触界面应力分布的影响。当涂层弹性模量比基底大时,涂层的存在使得接触半宽减少,最大名义接触应力增加;涂层弹性模量比基底小时,则与之相反。当涂层的厚度<0.01mm时,涂层的存在对固体润滑滚子轴承的接触表面应力分布影响较小;在一定范围内,当涂层的厚度逐渐增大时,涂层对轴承接触表面应力分布的影响增大。     

Rolling contact fatigue performance of detonation gun coated elements

Rolling contact fatigue performance of thermal spray coatings has been investigated using an experimental approach. A modified four ball machine which simulates a rolling element bearing was used to examine the coating performance and failure modes in a conventional steel ball bearing and hybrid ceramic bearing configurations. Tungsten carbide (WC-15% Co) and aluminium oxide (Al₂O₃) were thermally sprayed using a super D-Gun (SDG2040) on M-50 bearing steel substrate in the geometrical shape of a cone. A coated cone replaced the upper ball that contacts with three lower balls. The rolling contact fatigue (RCF) tests were performed under immersed lubricated conditions using two different lubricants. Fatigue failure modes were observed using a scanning electron microscope. Microhardness measurements of the coating and the substrate and elastohydrodynamic fluid film thickness results are included. The results show the requirement for significant optimization of the coating before use in rolling element bearing applications. The coating was fractured in a delamination mode. Test results show an optimization in coating process is required before these coatings can be used for rolling contact applications. WC-Co coatings perform better than Al₂O₃ coatings in rolling contact.     

滚动轴承疲劳破坏机理和疲劳寿命模型综述

延长轴承疲劳寿命,尤其是滚动轴承的接触疲劳寿命.一直是轴承工作者十分重视的研究课题.本文概括了滚动轴承接触疲劳破坏机理的主要形式和形成原因,总结了不同阶段的滚动轴承接触疲劳寿命计算公式,分析了不同滚动轴承接触疲劳寿命模型的区别.介绍了表面涂层的摩擦学性能在滚动轴承中的应用.     

A Model for Rolling Bearing Life with Surface and Subsurface Survival—Tribological Effects

Until now the estimation of rolling bearing life has been based on engineering models that consider an equivalent stress, originated beneath the contact surface, that is applied to the stressed volume of the rolling contact. Through the years, fatigue surface–originated failures, resulting from reduced lubrication or contamination, have been incorporated into the estimation of the bearing life by applying a penalty to the overall equivalent stress of the rolling contact. Due to this simplification, the accounting of some specific failure modes originated directly at the surface of the rolling contact can be challenging. In the present article, this issue is addressed by developing a general approach for rolling contact life in which the surface-originated damage is explicitly formulated into the basic fatigue equations of the rolling contact. This is achieved by introducing a function to describe surface-originated failures and coupling it with the traditional subsurface-originated fatigue risk of the rolling contact. The article presents the fundamental theory of the new model and its general behavior. The ability of the present general method to provide an account for the surface–subsurface competing fatigue mechanisms taking place in rolling bearings is discussed with reference to endurance testing data.     

超声速等离子喷涂Ni60A涂层的滚动接触疲劳寿命*

制备高质量的超声速等离子喷涂Ni60A涂层,并研究该涂层的滚动接触疲劳性能及寿命。通过正交试验对Ni60A涂层的4个主要喷涂工艺参数(喷涂电压、喷涂电流、Ar气流量和喷涂距离)进行优化设计,通过分析孔隙率和显微硬度值的大小,综合评价喷涂层质量。利用Image J2x孔隙率计算软件计算涂层孔隙率,利用扫描电镜分析Ni60A粉末和喷涂层的微观结构,采用显微硬度计测定涂层的显微硬度,利用RM-1接触疲劳/磨损多功能试验机对涂层进行不同载荷条件下的接触疲劳试验,并建立Weibull失效概率图。结果表明,通过正交试验可以获得高质量的超声速等离子喷涂Ni60A涂层,超声速等离子喷涂Ni60A涂层的最优喷涂工艺参数为：喷涂电压170 V,喷涂电流370 A,Ar气流量110 L/min,喷涂距离110 mm,通过最优参数制备得到的Ni60A涂层的孔隙率为1.05%,显微硬度为1 086 HV_0.2;在不同接触应力水平下,Ni60A涂层的寿命服从Weibull分布,通过Weibull失效概率图可以在一定范围内预测某一工作载荷下涂层的接触疲劳寿命。     

Durability of plasma-sprayed Cr3C2-NiCr coatings under rolling contact conditions

The aim of this paper was to address the rolling contact fatigue (RCF) failure mechanisms of plasma-sprayed Cr3C2-NiCr coatings under different tribological conditions of contact stress. Weibull distribution plots of fatigue lives of the coated specimens at different contact stresses were obtained. The failure modes of coatings were identified on the basis of wore surface observations of the failed coatings. Results showed that the RCF failure modes can be classified into four main categories, i.e., surface abrasion, spalling, cohesive delamination, and interfacial delamination. The probabilities of the surface abrasion and spalling type failures were relatively high at low contact stress. When the coatings were subjected to abrasion and spalling type failures, the failure of the coating was depended on the microstrcture of the coating. The stress concentration near the micro-defects in the coating may be the may reason for the formation of spall. The coatings were prone to fail in delamination under higher contact stresses. However, the delamination of coating may be related to distribution of shear stress amplitude within coating. The location of maximum shear stress amplitude can be used as a key parameter to predict the initiation of subsurface cracks within coating in rolling contact.     

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。     

考虑疲劳故障的圆柱滚子轴承打滑失效分析

考虑滚道疲劳剥落故障、滚动体与保持架之间的非连续接触等因素,建立圆柱滚子轴承的非线性弹性接触显式动力学模型,研究不同剥落故障位置、径向载荷、内圈转速对滚动体和保持架打滑特性的影响规律;将仿真结果与理论解进行对比,验证有限元模型的有效性。研究结果表明:滚动体在非承载区更容易出现打滑;相同工况下剥落故障会使得滚动体和保持架的打滑率大幅增加,其中复合故障下的打滑率增加最多,内圈故障和外圈故障下的打滑率增幅基本相同;增大径向载荷能有效减轻轴承的打滑现象,但载荷增加到一定程度后对打滑的抑制效果不明显;低转速工况下内圈和外圈疲劳故障对轴承打滑率的影响不大,随着转速的提高疲劳故障对打滑率的影响愈加明显。     

Residual stresses and retained austenite evolution in SAE 52100 steel under non-ideal rolling contact loading

Residual stresses are introduced and modified during manufacturing as well as by normal use under rolling contact loading. Operations such as heat treatments, shot peening, grinding, etc., are known to alter the magnitude and distribution of residual stresses. Our work revolves around the changes in magnitude and distribution of residual stresses, as they relate to deformation and the strain induced transformation of retained austenite. The residual stresses and retained austenite measurements were carried out using X-ray diffraction techniques. The rolling contact fatigue lives of different variants of SAE 52100 bearing steel were evaluated in a 5-ball-rod rolling contact fatigue machine under testing conditions leading to surface nucleated failure, i.e. non-ideal rolling contact. The tests were accelerated by applying well controlled micro-indentations on the wear track. The contribution of the residual stresses and amount of retained austenite to the rolling contact fatigue life were analyzed.