表面合金涂层提高铸铁齿轮的接触疲劳强度研究

接触疲劳破坏是铸铁齿轮的主要失效形式之一，本文研究在铸铁齿轮齿面涂镀Ni-P-Co合金层，以提高其接触疲劳强度，效果显著，同时，对合金涂层的表面形貌，次表面组织，纵剖面界面组织，表面粗糙度、涂层的硬度和疲劳点蚀坑形貌特征进行了分析。     

表面镍磷、镍钴合金镀层提高铸铁齿轮接触疲劳强度研究

研究了HT200灰铸铁齿轮轮齿表面Ni～P和Ni—Co合金镀层的工作性能,采用电子显微镜、光学显微镜等对合金镀层进行了表面形貌、纵剖面界面组织、合金镀层成分,显微硬度等的分析,接触疲劳的试验结果表明能显著提高接触疲劳寿命。     

表面合金涂层提高球墨铸铁齿轮抗点蚀性能的研究

本文以齿轮为研究对象，用常见的辊子模拟方法，在球墨铸铁试验辊子表面分别涂镀铜金属层、镍钨合金层和镍钴合金层，然后与未涂镀辊子一起进行接触疲劳强度对比试验（试验辊子４０对）。结果表明，表面合金涂层能显著地提高球墨铸铁齿轮接触表面的疲劳寿命。文中还分析了合金涂层的组织结构和性能。     

汽车变速器表面涂层齿轮疲劳性能试验与接触强度研究

在齿面制备减摩涂层可以有效地改善接触条件,提高齿轮疲劳寿命。文中主要研究减摩涂层对齿轮接触强度的影响规律。首先,在SRV标准试件表面制备涂层,通过摩擦磨损试验获得涂层试件间摩擦因数变化曲线;其次,对无涂层和有涂层的汽车自动变速器齿轮进行疲劳耐久试验,通过测量得到试验后齿轮的表面形貌特征;最后,根据齿轮非线性弹塑性接触理论,建立粗糙表面的齿轮接触强度分析模型,得出减摩涂层在提高齿轮接触疲劳强度中的作用。研究结果表明,磷酸锰转化涂层通过降低齿轮接触应力从而可以提高齿轮的疲劳耐久寿命;齿轮最大接触应力随粗糙度呈现先降低后升高的趋势。为涂层齿轮强度设计提供理论指导。     

高温合金激光表面熔铸Ni基合金涂层热疲劳性能研究

研究了高温合金ＧＨ３３激光表面熔铸Ｎｉ基合金涂层的热疲劳性能。结果表明，每次热循环后，熔铸层中的最终残余应力是残余热应力与组织应力共同作用的结果，经一定次数热循环，涂层组织形貌仍遗传了激光熔铸时的形貌，但枝晶变粗大；多次热循环后，涂层出现蚀坑，且多在涂层与基材接合处出现。涂层疲劳损伤形式为应力腐蚀。     

表面合金镀层和合金化提高铸铁机械零件接触疲劳强度研究

研究了HT250铸铁材质机械零件表面涂镀N1-P与Ni-CO合金镀层和合金化后的工作性能,采用电子显微镜,光学显微镜等对复合强化后的镀层表面形貌、次表面组织、纵剖面组织,表面粗糙度,镀层及合金化后的硬度、镀层成份、镀层与基体的结合强度等进行了分析.试件的接触疲劳试验结果表明能显著提高接触疲劳寿命.     

航空齿轮齿面失效分析

对航空用16NCD13钢渗碎淬火齿轮进行了化学成分，金相组织分析，对该材料齿轮进行了齿面接触疲劳试验，通过电子显微镜观察齿面失效形貌，并分析失效形成的原因和发展规律。     

碳氮共渗齿轮接触疲劳寿命的研究

通过25MnTiBRe钢和20CrMnTi钢齿轮共渗层浓度，表面硬度，硬化层深度的分析，化学成分作用的讨论，金相组织级别和特征的对比，缺口敏感性实验和接触疲劳的试验，研究了不同共渗层的疲劳寿命，探讨了提高寿命的途径。     

含纳米银粉润滑剂抗接触疲劳性能研究

制备了含纳米银粉的二相流体润滑剂，利用球-棒式接触疲劳试验机研究了纳米银粉对GCr15钢球和钢棒的接触疲劳性能的影响，并借助于扫描电子显微镜分析了钢球接触表面的疲劳点蚀形貌。结果表明：与基础油(10^#机械油)相比，含1％纳米银粉的润滑剂可使GCri5钢球的接触疲劳寿命L10提高3．54倍。其主要原因在于纳米银粉吸附于接触表面形成低剪切膜，降低了摩擦系数．减小了接触表面的切向应力，延缓了疲劳裂纹扩展速度。     

超硬涂层轴承的滚动接触疲劳试验

介绍了超硬涂层轴承滚动接触疲劳试验机的原理及功能,并对表面涂层的51306型轴承滚动接触疲劳失效进行了试验分析。通过对影响涂层接触疲劳破坏的几个重要参数的动态检测与控制,试验成功捕捉到了超硬涂层轴承表面疲劳裂纹的初始形态,分析了涂层轴承接触疲劳失效机理,为涂层轴承疲劳寿命评估提供了依据。     

Effects of humidity and contact material on fretting fatigue behavior of an extruded AZ61 magnesium alloy

Fretting fatigue tests of the extruded AZ61 magnesium alloy with the same contact material under low and high humidity were carried out to investigate basic fretting fatigue characteristics and effect of humidity on fretting fatigue behavior. Influence of contact material was also studied by using JIS S45C carbon steel contact material. Degradation of fatigue strength due to fretting was much more significant than that due to corrosion under high humidity condition. Therefore, no effect of humidity on fretting fatigue strength was found. Reduction rate of fatigue strength due to fretting for the magnesium alloy was between those of aluminum alloys and titanium alloys. Tangential force coefficient of the magnesium alloy was rather low compared to other materials such as steels, aluminum alloys and titanium alloys. Fretting fatigue strength with the S45C contact material was inferior compared to that with the same contact material. This is mainly due to higher tangential force in AZ61/S45C contact. Fretting fatigue cracks at the edge of fretting contact region were observed to nucleate in the very early stage of fatigue life, similar to other structural materials.     

Assessment and application of TiB2 coating in sliding pair under lubrication conditions

The aim of the present work is to determine the influence of TiB₂ coating on the friction parameters in sliding pairs under lubricated friction conditions. The TiB₂ coating deposited on modified surface layers of ring specimens made of AISI 5045 steel was matched under test conditions with counterparts made from SAE-783 and SAE-48 bearing alloys. Tested sliding pairs were lubricated with 5 W/40 Lotos synthetic engine oil. Tribological properties of the TiB₂ coating were measured using a block-on-ring tribometer. The applied modification technology of the surface layer of steel allowed for obtaining construction material with pre-determined tribological characteristics required for the elements of sliding pairs in lubricated contact. The results showed differences in the wear of bearing alloys, as a result of the interaction between co-operating surface layers and of the physiochemical changes of their surfaces, induced by external forces. Friction resistance and temperature in the friction area in the pair with TiB₂ coating and the SAE-783 bearing alloy are considerably higher than in the pair with the SAE-48 bearing alloy. The SAE-48 bearing alloy is subjected to more intensive wear processes in contact with the TiB₂ coating than the SAE-783 bearing alloy.     

风电齿轮箱行星齿轮用连铸坯的试验研究

为了验证合金钢连铸坯作为兆瓦级风电齿轮箱行星齿轮原材料是否能满足设计要求,在控制合金钢连铸坯冶金质量的前提下,进行试验研究.具体试验包括旋转弯曲疲劳试验、齿根弯曲疲劳试验、齿面接触疲劳试验等.最终得到的试验数据表明,对于内孔不小于300 mm的行星齿轮而言,使用合金钢连铸坯作为原材料,能够满足设计要求.     

LZ50钢车轴的旋转弯曲疲劳性能

在LZ50钢车轴上制取了光滑试样和环形缺口试样,按照AAR M-101-2009新标准测试了其旋转弯曲疲劳性能,并观察了断口形貌。结果表明:光滑试样的旋转弯曲疲劳裂纹萌生于试样表面,而环形缺口试样的裂纹萌生于缺口前缘,并呈多源开裂形式,两种试样均形成与轴向垂直的平断口;当车轴的拉伸强度提高5%后,其光滑试样旋转弯曲疲劳性能也得到明显提高,环形缺口试样虽中值疲劳强度比光滑试样的降低18%,但其旋转弯曲疲劳极限缺口敏感系数仍与国外碳素钢车轴保持在同一水平上。     

等离子喷涂NiCrBSi涂层接触疲劳过程中残余应力变化规律研究

采用超声速等离子喷涂技术在45钢基体上制备NiCrBSi合金涂层,涂层整体结构致密,含有少量微缺陷。使用球盘式接触疲劳试验机在接触应力为1.86 GPa,转速为1 500 r/min的条件下对涂层试样进行接触疲劳试验,得到涂层的接触疲劳寿命为9.0×105周次;同时建立Weibull失效概率图,通过该图可以直观地得到在同一工作条件下,涂层任意循环次数的失效概率。测量涂层不同疲劳阶段的残余应力,结果表明:一旦进行接触疲劳试验,其残余应力形式由拉应力迅速转化为压应力,在整个疲劳过程的前半段,应力增强较为缓慢,在疲劳过程的后半段,应力值迅速增大,疲劳过程的中期成为了应力变化的转折点。根据这一规律,可以有效地判定涂层处于疲劳过程的哪个阶段,从而为预防涂层的突然失效提供了一种新的手段。     

Influence of undercoating on rolling contact fatigue performance of Fe-based coating

The aim of this paper was to address the influence of undercoating on the rolling contact fatigue (RCF) performance of coatings. The Fe-based alloy and Ni/Al alloy were deposited on substrates as surface coating and undercoating by plasma spraying. The failure modes were investigated for two kinds of coatings. RCF performances were compared using Weibull distribution plot. The results showed undercoating played an important role on increasing RCF life of coating for the higher bond strength, and decreasing the scatter of RCF life data. The deposited undercoating could influence the failure mode of coating and prevent the occurrence of catastrophic delamination.     

论高强度螺栓的材料及其强度问题

本文从高强度螺栓的服役条件出发论述了高强度螺栓选材的考虑因素。用低碳马氏体钢和中碳调质钢进行了静拉伸、偏斜拉伸、冲击韧性、疲劳强度和延迟断裂强度等试验。试验结果表明,与中碳调质钢相比,低碳马氏体钢的强度提高1/3以上,同时保持较高的塑性和韧性,螺栓的承载能力提高45～70%,而缺口偏斜敏感性并不显著升高;螺栓的疲劳强度与中碳钢调质态螺栓大体相同：低碳马氏体钢的延迟断裂敏感性比相同强度水平的40Cr钢小,并且在盐水和水中对延迟断裂是不敏感的。因此,选用低碳马氏体钢作高强度螺栓材料,不仅在综合机械性能方向有许多优点,而且其优良的工艺性能更是中碳钢不能比拟的。本文还进行了热处理前和后滚制螺纹对螺栓疲劳强度的影响试验,结果表明,热处后滚制螺纹可有效地提高螺栓的疲劳强度。根据本文的试验结果,作者对低碳马氏体螺栓钢的成分设计作了某些探讨。     

热浸镀55%Al-Zn后钢的拉伸性能和耐蚀性能研究

研究了热浸镀55%Al-Zn合金镀层钢的室温拉伸性能和耐蚀性能。结果表明：Q235钢板经热浸镀55%Al-Zn合金后的室温屈服强度和抗拉强度均高于Q235钢，而伸长率没有降低。经SEM观察，55%Al-Zn合金镀层钢的拉伸断口由钢基体的韧窝断口和Fe-Al-Zn-Si合金层的穿晶解理断口组成。腐蚀试验结果显示：热浸镀55%Al-Zn合金后钢的耐蚀性在盐雾中是镀锌钢的6倍，在盐水中是镀锌钢的3倍，并同样具有镀锌层对钢基体的电化学保护能力。     

Relationship between the propagation of fatigue cracks and the behaviour of plastic flow under rolling/sliding contacts - effect of slip ratio

The relationship between the propagation of fatigue cracks and the behaviour of plastic flow in the surface layer was experimentally investigated under lubricated rolling-sliding contact. The test specimen material was medium carbon steel (S45C) with hardness H_v 187 after annealing. Results show that the displacement of plastic flow in the surface layer of the follower increased with increasing number of revolutions. Crack propagation occurred in the surface layer of the follower when the displacement of plastic flow on the centre of the contact reached a saturated value. On the contact surface of the follower, the propagating angle of the fatigue crack was found to be correlated to the angle of plastic flow, which was independent of the slip ratio. The rate of plastic flow increased with increasing slip ratio, resulted in a reduction of fatigue life. The displacement of plastic flow beneath the contact surface could be evaluated from the profile change of the plastic flow on the contact surface.     

四球机改装的接触疲劳试验机及其应用

作者将四球机改装成接触疲劳试验机，并在其上进行了一系列添加剂对接触疲劳的影响试验研究。认为该装置具有接触应力大，体积小，噪声小，一次试验耗油量小，试验系统传动稳定，试验结果可信等优点。接触疲劳试验结果认为添加剂的各种性能之间相互作用和综合效果，才是影响疲劳寿命的关键。