氮化硅混合陶瓷球轴承滚动接触疲劳性能

介绍了氮化硅陶瓷球及氮化硅混合球轴承滚动接触疲劳性能的典型试验方法，分析了氮化硅混合球轴承的滚动接触疲劳性能及其影响因素，探讨了氮化硅混合陶瓷球轴承滚动接触疲劳寿命的估计方法。     

点接触纯滚动被试轴承球润滑性能研究

润滑工况是滚动接触疲劳寿命的主要影响因素之一,而润滑剂、接触形式等因素都对润滑状态有所影响。采用新研制的三点接触纯滚动轴承球加速疲劳试验机,研究了被试球钢球和陶瓷球在润滑油N32润滑下的润滑性能,并计算了最小油膜厚度及润滑膜参数,分析了润滑状态。结果表明,所用的润滑油N32是合适的,被测试的钢球和陶瓷球工作在弹性流体动力润滑(EHL)状态。分析结果为钢球和陶瓷球的对比滚动接触疲劳性能试验提供了理论基础。     

氮化硅陶瓷球滚动接触疲劳寿命模型

针对球与圆柱接触模型中的陶瓷球,利用WEIBULL断裂统计方法导出球疲劳失效概率与寿命之间的关系方程,在相关额定寿命与最大接触应力的数值解基础上,基于最大主拉应力,构建氮化硅陶瓷球的滚动接触疲劳寿命与接触应力的数学模型.经与不同接触应力水平下的滚动接触疲劳寿命试验结果验证,表明该拉应力一寿命模型的正确性,从而验证了氮化硅陶瓷球的滚动接触疲劳失效源于最大主拉应力,而非基于最大切应力的设想.通过与L.P切应力一寿命模型预测结果的比较,表明拉应力一寿命模型适合于陶瓷球的接触疲劳寿命预测.     

陶瓷球和钢球接触疲劳寿命对比试验

陶瓷球的滚动接触疲劳寿命是评价陶瓷球能否用于滚动轴承的重要依据，为了确保陶瓷球的可靠性，最大限度地延长其使用寿命，利用新研制的三点接触纯滚动加速疲劳试验机对陶瓷球和钢球进行了对比试验。结果表明，与GCr15钢球相比，氮化硅陶瓷球的温升明显低于钢球；额定寿命低于钢球，中值寿命与特征寿命优于钢球。     

润滑油添加剂对陶瓷球接触疲劳的影响

利用自制的球-棒疲劳试验机研究了4种润滑油添加剂对Si3N4与GCr15钢摩擦副接触疲劳性能的影响，并借助于扫描电镜(SEM)和X射线能量色散谱(EDAX)分析了Si3N4陶瓷球表面疲劳成因及不同添加剂的抗疲劳机理。结果表明，4种添加剂都不同程度地提高了Si3N4陶瓷球的接触疲劳寿命，其中以极压抗磨剂效果较好；点蚀剥落是Si3N4陶瓷球的主要失效形式；添加剂抗疲劳的主要原因是在钢表面形成反应膜，在陶瓷球表面形成转移膜，降低了滑动摩擦力。     

纯滚动状态下氮化硅陶瓷球临界应力分析

氮化硅陶瓷球临界应力在很大程度上决定其滚动接触疲劳和磨损寿命.由于陶瓷材料的抗拉能力较弱,所以设想其滚动接触疲劳失效的临界应力为最大主拉应力.应用弹性接触力学和赫兹理论分析纯滚动条件下陶瓷球表面层接触应力,得到表面层最大主拉应力.针对理论计算值,设计相应的纯滚动接触疲劳实验.分析表明,理论值与实验结果趋于一致,从而证实最大主拉应力为氮化硅陶瓷球滚动接触疲劳失效的临界应力.计算结果为陶瓷球的滚动接触疲劳寿命分析提供理论基础.     

Si3N4陶瓷球的滚动接触疲劳寿命试验研究现状与展望

对氮化硅陶瓷球的滚动接触疲劳试验技术进行了全面的归纳总结和分析评述,内容涵盖了陶瓷球试验装置和试验研究等,分析了我国在陶瓷轴承球基础理论研究及工程应用中的现状及在技术层面上所面临的严峻挑战,并提出了相应的对策和建议。     

Si3 N4陶瓷球的滚动接触疲劳寿命

对氮化硅陶瓷球的滚动接触疲劳试验技术进行了全面的归纳总结和分析评述,内容涵盖了陶瓷球试验装置和试验研究等,分析了我国在陶瓷轴承球基础理论研究及工程应用中的现状及在技术层面上所面临的严峻挑战,并提出了相应的对策和建议.     

在重载荷接触下喷气发动机燃料的工作特性

对在有JP-8＋100喷气发动机燃料和Mil-L-23699涡轮喷气发动机油的情况下工作的钢和陶瓷（氮化硅）材料的摩擦系数、轴承性能（即力矩产生和温升）及滚动接触疲劳进行了试验。使用球对盘试验机,测量在不同载荷和滑滚比下,用JP-8＋100喷气发动机燃料润滑时,运转的钢球对钢盘的摩擦系数。结果表明,在这个试验设想的条件下,燃料提供极低的摩擦系数。使用三球对拉杆滚动接触疲劳试验机测定材料（即氮化硅和钢材）和润滑油不同组合的疲劳寿命。像期盼的那样,Weibull分析表明在有喷气发动机燃料情况下运转的滚动疲劳寿命小于油润滑接触的。也设计、研制了轴承试验机,并用其获得在喷气发动机燃料和油中运转的轴承的摩擦（力矩）和温度性能。轴承试验结果表明燃料比油产生的力矩和温升低。     

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。     

VOLUME DEFECT FATIGUE FAILURE OF CERAMIC BALLS UNDER ROLLING CONDITION

A newly developed pure rolling fatigue test rig with three contact points is used to test the rolling contact fatigue properties of silicon nitride ceramic balls. Ball surfaces are examined after failure with optical microscopy and scanning electron microscopy. The failure cause,fatigue phenomenon and mechanics are analyzed. The research shows that subsurface cracks play a dominant role in the formation of spalling failure. These cracks originated from volume defects of the material and propagate,to form elliptical fatigue spalls under the action of principal tensile stresses. The principal tensile stress increases with increasing contact load,causing spall formation and reduction of rolling contact life. The greater the principal tensile stress is,the more severe the peeling of near surface is. Under the same condition,the closer volume defects are to the surface,the more likely failure occurs,the shorter the rolling contact life is.     

Experimental Study of Cyclic Rolling-Contact Fatigue of Silicon Nitride Balls

A newly developed pure-rolling fatigue test rig with three contact points for bearing balls was used to perform rolling-contact fatigue (RCF) tests. The fatigue properties of GCr ₁₅ steel balls and two kinds of Si ₃ N ₄ ceramic balls (GSN-200 and NBD-200) produced with different technologies were compared. Life test data, summarized in accordance with the Weibull theory, showed that the life of the GSN-200 balls was close to that of the GCr ₁₅ balls, whereas the life of the NBD-200 balls was much longer than those of GSN-200 and GCr ₁₅ . Under the same working condition, the temperature rise of all the ceramic balls was lower than that of the steel balls. Ball surfaces were examined after failure with optical microscopy and scanning electron microscopy. It was identified by test that the failure mode of ceramic balls was surface spall. The research shows that subsurface cracks play a dominant role in spalling failure. These cracks originated from volume defects of the material and propagate to form elliptical fatigue spalls.     

辗轧工序对车轮摩擦磨损和接触疲劳性能的影响

为研究辗轧工序对车轮使用性能的影响,选择经辗轧工序成形和直接钢水浇筑成形的2种车轮材料,利用GPM-30试验机开展摩擦磨损和接触疲劳性能研究,采用光学显微镜、扫描电子显微镜、ASPEX分析仪、EBSD分析2种车轮材料在不同接触应力状态下摩擦磨损和接触疲劳裂纹萌生扩展行为。结果表明:辗轧工序能够有效地细化车轮材料晶粒,减小珠光体片层间距,从而改善车轮微观组织,减少不均匀塑性变形,抑制裂纹的萌生和扩展,减少磨损量,延长接触疲劳寿命;同时发现夹杂物的形态影响接触疲劳试验亚表面裂纹的萌生。     

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.     

ROLLING CONTACT FATIGUE BEHAVIOR OF CERAMIC BALLS LUBRICATED BY LUBRICANTS WITH EXTREME PRESSURE ADDITIVES

An experiment is conducted to investigate the effects of lubricant10#, which contains extreme pressure additives T304 and T305, on the rolling contact fatigue (RCF) life of the contact pairs of a Si3N4 ceramic ball and a steel rod. The experimental investigation is carried out using a ball-rod RCF test rig. The results show that the extreme pressure additives increase the anti-contact-fatigue performance of ceramic balls; When the content of the additives varies from 1% to 5%, the increasing gradient of the RCF life curve decreases; And the oil sample with 1% T305 additive corresponds to the maximal gradient of the RCF life curve, with the RCF life being increased by about 10.77 times. The fatigue surface of the ceramic ball is analyzed with scanning electron microscope (SEM) and X-ray electron dispersion analysis(EDAX), and the physical model of extreme pressure additives' increasing the RCF life of the ceramic ball is proposed. It is found that the extreme pressure additives form a corrosive film and a transfer film on the surface of the ceramic ball, which decrease the surface tangential stress, and to increase the surface energy is the most effective means for increasing the RCF life.