Effects of Contact Pressure and Sliding Speed on the Unlubricated Friction and Wear Properties of Zn-15Al-3Cu-1Si Alloy

The unlubricated friction and wear properties of Zn-15Al-3Cu-1Si alloy were studied over a range of contact pressure (1–5 MPa) and sliding speed (0.5–2.5 ms^?1) for a sliding distance of 2,500 m using a block-on-disc type test machine. It was observed that as the contact pressure increased, the friction coefficient of the alloy decreased but its working temperature, surface roughness, and wear volume increased. Sliding speed had no significant effect on the friction coefficient of the alloy but increased its working temperature, surface roughness, and wear volume. It was also observed that the formation of a hard and brittle surface layer had a great influence on the wear behavior of the experimental alloy. The hardness and thickness of this layer increased with increasing contact pressure and sliding speed. However, contact pressure was found to be much more effective on the hardness of the surface layer of this alloy. Both adhesion and abrasion were observed to be the dominant wear mechanisms for the alloy under the given sliding conditions. The results obtained from the friction and wear tests are discussed in terms of the test conditions and microstructural changes that take place during sliding.     

MoSi2/45#钢在干摩擦条件下的滑动摩擦磨损性能

在MRH-5A型环-块型摩擦磨损实验机上,考察了MoSi2与调质45#钢配对时的摩擦磨损特性。运用KYKY2800型扫描电子显微镜,观察和分析了其磨损表面形貌,探讨了该材料的磨损机制。结果表明：在pv为284.96N.m.s^-1时,MoSi2与调质45#钢对摩时具有较低的摩擦因数和磨损率。在载荷和转速两影响因素中,转速的影响较大,低转速时MoSi2的磨损机制为粘着,且随着载荷的增加,出现粘着膜脱落;高转速时MoSi2材料表面粘着较低速时减弱。     

MoSi2/淬火45钢的干摩擦磨损性能

采用M-2型磨损试验机研究了MoSi2/淬火45钢的干摩擦磨损特性，并通过对电子扫描显微镜（SEM）和X射线衍射仪观察了试件的磨损表面形貌，分析了磨屑的成分，探讨了其摩擦磨损机理。结果表明，随着载荷的增大，摩擦机理主要表现为微观滑动和粘着效应，低载荷下的磨损机制以疲劳磨损为主，高载荷下的磨损机制主要表现为粘着磨损。     

An Investigation on Reasons Causing Inferiority in Unlubricated Sliding Wear Performance of 60NiTi as Compared to 440C Steel

60NiTi is gaining recognition as an alternative to 440C steel in ball bearing components due to its intrinsic corrosion resistance and unusually high static load capacity. 440C steel and 60NiTi exhibit comparable Rockwell hardness and would be expected to exhibit similar sliding wear behavior using hardness based models. However, results show that under unlubricated sliding conditions, 60NiTi shows inferior wear properties than 440C steel. In this study, a series of indentation and single pass scratching experiments are conducted to elucidate the reasons behind this unexpected observation. Moreover, sliding wear tests carried out under moderate and extreme tensile stress conditions were used to identify sliding conditions under which these materials exhibit similar and dissimilar behavior. The results show that 440C steel exhibits more microscopic plasticity than 60NiTi, halting the propagation of generated tensile microcracks. In contrast, the intrinsic brittleness of 60NiTi leads to the formation and growth of microcracks between the shear bands causing subsequent wear particle generation. These lead to the occurrence of wear through more aggressive abrasion processes in 60NiTi than 440C steel. These findings help explain why 60NiTi performs well when lubricated. 60NiTi is expected to tolerate ～912?MPa tensile stress before yielding. Under good lubricated conditions where a perfect lubricating film is formed, friction induced tensile stresses fall below the tensile strength of 60NiTi and wear is prevented. However, inadequate lubrication combined with high contact stress leads to damage and wear.     

润滑剂减缓微动磨损研究进展

综述了油、脂润滑减缓微动磨损的条件、作用机制,以及油、脂性能对微动磨损的影响等基础研究的进展.介绍了油、脂润滑减缓微动磨损的工业应用研究现状,以期为工业正确使用润滑油、脂降低微动磨损指明方向.     

惯性制动条件对铜-石墨材料摩擦性能及第三体的影响

采用粉末冶金技术制备铜-10%石墨烧结材料,通过GF150D型摩擦试验机,在干摩擦状态及制动压力为0.51 MPa的条件下,研究不同制动方式对材料摩擦磨损性能的影响。结果表明,采用从高速到低速分段制动方式(摩擦方式A)时,随着制动速度降低,摩擦表面形成的致密第三体破碎、剥落,机械啮合力增加,摩擦因数提高;同时,摩擦表面温度下降,基体强度提高,磨损率降低。采用从高速到低速连续制动方式(摩擦方式B)的摩擦因数和磨损量均大于摩擦方式A。     

25CrNi2MoV钢的微动磨损性能

采用微动摩擦磨损试验机在干摩擦条件下对新型高速重载传动轴用25CrNi2MoV钢进行微动磨损试验,研究了不同载荷(50~200N)和频率(15~30Hz)下该钢的微动磨损性能。结果表明:在频率为20Hz条件下,当载荷由50N增至200N时,25CrNi2MoV钢的平均摩擦因数由0.766减至0.661,磨损体积由19.65×10^-3 mm^3增至75.83×10^-3 mm^3;在载荷为30N条件下,当频率由15Hz增至30Hz时,平均摩擦因数由0.790增至0.905,磨损体积由11.43×10^-3 mm^3增至23.88×10^-3 mm^3;在不同试验参数下,25CrNi2MoV钢磨损表面均出现了氧化和犁沟现象,磨损机制包含氧化磨损和磨粒磨损;在频率为20Hz条件下,载荷为50,100N时,25CrNi2MoV钢的磨损机制以黏着磨损为主,载荷为150,200N时,主要磨损机制为疲劳磨损;在载荷为30N条件下,频率为15~25Hz时,磨损机制以磨粒磨损为主,当频率增至30Hz时,磨损机制以疲劳磨损为主。     

The Effects of Sodium Chloride Solution on Fretting Wear Behavior of Nickel Based Alloy in Partial Slip Regime

The investigations on fretting wear behaviors of nickel based alloy in NaCl solution and atmosphere indicated that wear mechanism and regional transformation from partial slip regime (PSR) to the mixed regime (MR) are significantly affected by NaCl solution. The crevice corrosion induced by synergy of chloride ion and deformed asperities caused wear mechanism changed from adhesive and oxidation wear (PSR in atmosphere) to abrasive and oxidation wear (PSR in NaCl solution) and to oxidation and delamination wear (MR in NaCl solution), meanwhile accelerated the regional transformation from PSR to MR. However, the annular fatigue crack was almost unaffected by NaCl solution, which propagated along the direction of 40-50^° to surface in the mode of transgranular and intergranular in all conditions.     

Effect of Cold Rolling on the Fretting Wear Behavior and Mechanism in Inconel 600 Alloy

The fretting test was carried out using an SRV IV fretting test rig in order to investigate the fretting wear behavior and mechanism in Inconel 600 alloy at room temperature. The materials were rolled to different reductions before the test. The effect of cold rolling on the friction coefficient and wear volume was subsequently investigated. The surface and cross-sectional morphologies of the wear scar were studied by scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), and electron back-scattering diffraction (EBSD). The results indicated that the cold rolling had a different effect on wear behavior in different slip regimes. In the stick regime, cold rolling strongly decreased the wear volume, although it did not affect the friction coefficient. The 25% rolled specimen had the minimum wear volume. The mechanisms of as-received and 50% rolled specimens were delamination and oxidation wear, whereas for the 25% rolled specimen, cracking was the main wear mechanism. In the gross slip regime, cold rolling had little effect on the friction coefficient or wear volume. The fretting wear process gave rise to a decrease in the Σ3 grain boundary, an increase in local misorientation, and a change in the crystal orientation.     

Finite Element Modeling and Experimental Validation of Fretting Wear Scars in a Press-Fitted Shaft with an Open Zone

A finite element (FE)-based method was developed for simulating the fretting wear scar in a press-fitted shaft with an open zone. The method is based on the energy wear approach and is implemented via the commercial FE code ABAQUS. The effects of open zone, mesh size, cycle jumps technique, and increments per fretting cycle were investigated for optimization of this methodology. The results show that when assuming that the surface profile can be changed only in the open zone, the FE wear model gives a good prediction of the scar width. The mesh size has a great influence on the dimensions and shape of the scar profile; when the mesh size is about 3% of the width of the wear scar for a press-fitted shaft, the best compromise between the wear scar shape and the computational time can be achieved. For the cycle jump ΔN, an optimum value of 3,000 is found; above this value, the depth of the fretting wear scar increases rapidly with increasing ΔN. The impact of increments per fretting cycle on the depth of the predicted wear scar is small by comparison with cycle jump ΔN. The results of the optimized model are validated with respect to the experimental data obtained in the interrupted fretting fatigue tests. The FE wear model can provide an accurate prediction of the maximum wear depth and the width of fretting wear scar. The predicted wear depth inside of the contact is slightly larger than that found experimentally.     

1045钢在部分滑移区和滑移区内的高温微动磨损性能研究

从室温到400℃，对GCr15钢与1045钢组成的摩擦副进行了微动摩擦拭验。法向载荷变化范围为100—300N、位移幅值为15—60μm。通过摩擦动力学分析，结合显微观测，发现1045钢的高温微动行为与微动区域特性密切相关。在滑移区内，随着温度的升高，摩擦系数与磨损降低，但在部分滑移区内，温度对微动行为影响很小。     

Differences in Mechanisms for Fretting Wear Reduction between Oil and Grease Lubrication

The different mechanisms of fretting wear in oil and grease lubrication and methods to reduce fretting wear were examined by means of thrust ball bearings in this study. Tests of fretting wear under oil lubrication were conducted. It was confirmed that high-viscosity oil can reduce fretting wear at high velocity (i.e., high frequency) through oil film formation. In the case of grease lubrication, the influence of velocity on fretting wear was significantly different for low- and high-viscosity greases. Grease with low-viscosity base oils could reduce fretting wear at high velocity. In contrast, grease with high-viscosity base oils could reduce fretting wear at low velocity. Grease thickeners were found to be effective in forming a layer that could prevent fretting wear. These results highlight the large differences in effective fretting wear reduction mechanisms between oil and grease lubrication.     

Fretting Wear Behavior and Mechanism of Inconel 690 Alloy Related to the Displacement Amplitude

Fretting wear tests on Inconel 690 alloy were carried out at different displacement amplitudes. The results indicated that with an increase in displacement amplitude, the ratio of tangential force to normal load and wear volume increased. The fretting mode gradually transformed from mostly stick, mixed stick–slip, to full sliding, showing the competition of fretting-induced fatigue cracking and fretting-induced wear. There was a gradient plastic strain created by fretting, which resulted in the formation of a nanocrystalline tribologically transformed structure (TTS) and plastic deformation layers. The plastic strain in the plastic deformation layer gradually increased with an increase in displacement amplitude.     

Investigation on the Fretting Wear Behavior and Mechanisms of Alloy 690TT during the Transformation from Mixed Regime to Partial Slip Regime Induced by Elevated Temperature

Fretting wear of Alloy 690TT can occur in the steam generator of a nuclear power plant, in which the interfacial conditions are changed as the temperature varies. In this study, the gradual transformation from the mixed fretting regime (MFR) to the partial slip regime (PSR) occurred with an increase in test temperature. Correspondingly, there was a competition in wear modes due to the formation of a nanostructured tribologically transformed structure (TTS), presence of delamination cracking, nucleation of fatigue cracks, and oxidation. Delamination within the TTS dominated first. As the area of TTS and the plastic deformation region was reduced, fatigue cracks began to initiate. Oxidation was accelerated by an increase in the test temperature, and that effect resulted in reduced wear volume of Alloy 690TT in the MFR.     

微动疲劳参数对钢丝微动疲劳磨损演化的影响*

微动疲劳易引起钢丝表面磨损和横截面积损失,进而造成钢丝断裂失效并缩短钢丝绳使用寿命。不同微动疲劳参数（接触载荷、疲劳载荷、钢丝直径和交叉角度）引起差异的钢丝微动疲劳磨损特性,故研究微动疲劳参数对钢丝微动疲劳磨损演化规律影响至关重要。基于摩擦学理论和Marc仿真软件构建钢丝微动疲劳磨损模型,探究接触载荷、疲劳载荷、交叉角度和钢丝直径对钢丝微动疲劳磨损演化的影响规律。结果表明：钢丝微动疲劳磨损体积主要与接触载荷和疲劳载荷有关;疲劳钢丝的磨损深度、磨损率及磨损体积随着接触载荷的增加而增大,且不同接触载荷下疲劳钢丝磨损体积均随着循环次数的增加而呈线性增加;随疲劳载荷幅值的增加,疲劳钢丝的磨损深度、磨损率及磨损体积均呈增加趋势;在不同疲劳载荷范围下疲劳钢丝的磨损体积均随着循环次数的增加而呈线性增加;当接触载荷、疲劳载荷及钢丝间摩擦因数相同时,不同交叉角度和不同加载钢丝直径下疲劳钢丝的磨损体积相同。     

ZM5镁合金微动磨损特性研究

采用高精度微动试验台研究了ZM5镁合金的微动磨损行为,法向载荷变化范围为50～200N、位移幅位为5～40μm。通过摩擦力-位移-循环次数变化分析,结合显微观测,结果表明:ZM5镁合金的微动磨损行为与微动区城特性密切相关。它的微动损伤形貌主要是磨损,在初期阶段的磨损机制主要是粘着和氧化,中后期是粘着、氧化和磨粒磨损共同作用的结果。     

高分子聚合物材料微动摩擦磨损行为

组合密封中塑料环的耐磨特性对其密封性能有重要作用,为优选合适对摩材料,研究超高分子量聚乙烯(UHMWPE)、聚四氟乙类(PTFE)+40%铜粉、PTFE+7%碳纤维、PTFE+7%碳纤维+5%MoS₂、聚醚醚酮(PEEK)5种高分子聚合物材料与QT500对摩的微动摩擦磨损性能。从中筛选出PTFE+7%碳纤维、UHMWPE 2种材料进行不同微动行程、润滑条件下的对比试验。结果表明：无论是在干摩擦还是油润滑条件下,UHMWPE材料的平均摩擦因数随着微动行程的增大而增加,PTFE+7%碳纤维材料达到稳定状态时摩擦因数随着循环次数的波动较小。综合试验结果,当微动行程小于等于0.2 mm时建议选用PTFE+7%碳纤维,微动行程大于0.2 mm时建议选用超高分子量聚乙烯材料。     

不锈钢焊接区金属微动磨损行为研究

以1Cr18Ni9Ti不锈钢材料为母材,采用焊条电弧焊方法制备焊件。在焊接检验合格的焊态试件上从焊缝区、熔合区和焊接热影响区金属中分别截取并制备微动磨损试验用试样。将制备好的焊接区不同位置金属试样在相同条件下进行微动磨损试验,研究焊接区金属微动磨损行为。研究结果表明,在选定的微动磨损试验参数下,微动处在完全滑移区;焊接区不同部位金属的微动磨痕形貌存在差异,具有不同的微动磨损行为。焊缝区金属磨痕最大深度差异不明显,但磨痕平面投影面积差异显著。焊接热影响区金属磨痕最大深度差异显著,而磨痕平面投影面积差异不明显。     

Reciprocating Sliding Wear Behavior of 60NiTi As Compared to 440C Steel under Lubricated and Unlubricated Conditions

ABSTRACT

60NiTi is a hard (～60 HRC) and highly corrosion-resistant intermetallic with a relatively low elastic modulus (～100 GPa). In addition, this alloy exhibits a high compressive strength (～2,500 MPa) and a high elastic compressive strain of over 5%. These attributes make this alloy an attractive candidate to be employed in structural and mechanical component applications. However, sliding wear behavior of this intermetallic has not yet been studied in a systematic way. In this study, lubricated and unlubricated reciprocating sliding wear behavior of 60NiTi is compared to 440 C steel as a conventional bearing and wear-resistant alloy. Results of experiments carried out under different loads show that 60NiTi, despite having a higher hardness, exhibits a significantly inferior wear behavior under dry conditions in comparison to 440 C steel. These unexpected results indicate that 60NiTi does not follow conventional wear theories where the wear of materials has an inverse relationship to their hardness. On the other hand, under lubricated conditions with castor oil and a synthetic gear oil, 60NiTi exhibits low specific wear rates. These results exhibit the importance of proper lubrication in sliding mode applications where 60NiTi is exploited as a wear-resistant alloy.     

电连接器微动磨损的超声识别与性能退化模型

针对振动环境下电连接器易产生微动磨损而接触性能降低这一问题,采用超声检测方法监测微动磨损过程中电连接器接触件间磨屑的特征值,研究了不同振动条件下接触件的磨损程度及接触性能的退化规律。结果表明,振动频率、振动加速度和振动次数对接触面磨屑的堆积和接触电阻的波动都有正向累积效应;电连接器轴向振动时,磨屑累积效应最为明显。接触电阻和磨屑特征值总量在高振频及加速度下呈现极高的相关性。以磨屑特征值构建的麻雀搜索算法优化BP神经网络性能退化模型的平均绝对误差小于5%。