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.     

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.     

Effects of Loading and Sliding Speed on the Dry Sliding Wear Behavior of Mg-3Al-0.4Si Magnesium Alloy

The friction and wear properties of Mg-3Al-0.4Si alloy were investigated using a pin-on-disc tester. Morphologies and compositions of worn surfaces were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) for identification of the wear mechanisms. Microstructural evolution and hardness change in subsurfaces were analyzed by confocal scanning laser microscopy and hardness testing. The results revealed that the wear behavior of Mg-3Al-0.4Si alloy was classified into two types of wear regimes; that is, mild and severe. In the mild wear regime, wear rates increased at a low slope with increasing load; the corresponding wear mechanisms were oxidation, abrasion, and delamination. In the severe wear regime, wear rates increased rapidly at a high slope with load; the wear mechanisms were severe plastic deformation and surface melting. Analysis of microstructural evolution on the subsurface identified the reason for the transition from mild to severe wear; that is, the realization of dynamic recrystallization (DRX) in the surface layer material. A contact surface DRX temperature criterion for the mild to severe wear transition was proposed, and the critical DRX temperatures for the mild to severe wear transition were calculated using DRX kinetics.     

Influence of Temperature and Relative Humidity on the Friction and Wear of Unlubricated Reciprocating Sliding Steel/ Steel Couples

Many tribosystems are subjected to different conditions with respect to temperature and humidity. Reciprocating sliding tests with steel/steel couples were performed using a laboratory test rig in air with varying relative humidity and temperature. During each test the friction force, the total linear wear, the electrical contact resistance, and the acoustic emission were recorded. Tests with self‐mated couples of bearing steel (100r6) and of stainless steel (X10CrNiMoNb18‐10/X5CrNi18‐9) in a ball‐on‐disc arrangement revealed small effects of temperature and humidity on friction, but a strong effect of the water vapour content on the wear rate of the system. Attempts were made to correlate changes of wear behaviour with different wear mechanisms.     

Influence of Normal Force and Humidity on the Friction and Wear of Unlubricated Reciprocating Sliding Steel/Steel Couples

The friction and wear behaviour of different steel/steel couples was investigated in laboratory tests with unlubricated reciprocating sliding motion. Two different steel balls were tested against two different steel discs in dry, normal, and moist air at room tem‐perature. The influence of normal force on friction and wear was studied in the range from 1 to 10 N for all three levels of relative humidity (RH). RH strongly influenced wear behaviour for all four couples, while the friction behaviour was less affected by RH. For all the couples, normal force was found to influence wear rate with a tendency for the wear rate to increase with decreasing normal force. The coefficient of friction also increased with decreasing normal force, but to a much lesser extent than that evaluated for the wear rate.     

不同介质下ER8车轮钢滑动摩擦磨损性能

为探讨车轮在不同环境下服役时摩擦因数的变化机制,通过滑动摩擦试验机考察不同载荷下,ER8车轮钢分别在干燥空气、纯水、3.5%氯化钠溶液3种环境下的摩擦磨损性能。利用光学显微镜、扫描电子显微镜、非接触三维表面轮廓仪、X射线衍射仪对磨痕及元素组成进行了分析,探讨不同环境下ER8车轮钢的摩擦磨损机制。结果表明：随着载荷的增大,ER8车轮钢的摩擦因数明显增大;列车的服役环境对车轮的摩擦磨损性能有较大影响,在干燥空气环境下,ER8车轮钢无腐蚀状况,磨痕宽度最小,但摩擦因数最大,可达0.503;在盐水环境下,ER8车轮钢出现腐蚀现象,磨痕宽度最大,但摩擦因数最小;干摩擦下ER8车轮钢的磨损机制为黏着磨损、磨粒磨损和氧化磨损,纯水摩擦和3.5%NaCl溶液环境下的磨损机制为磨粒磨损和氧化磨损。     

Investigation of the Transition State in the Wear of Polyphenylene Sulfide Sliding Against Steel

The effect of sliding variables, including counterface roughness, sliding speed, and contact pressure, on the run-in state of wear and friction was studied. Sliding was performed in the pin-on-disk configuration with a polyphenylene sulfide (PPS) pin resting on the flat steel counterface. Some experiments were also run to study the effect of air cooling and heating. Optical microscopy and scanning electron microscopy were used to study the shape and size of the wear debris, worn pin surface, and the transfer film formed on steel counterfaces. It was found that friction and wear in the run-in state were significantly affected by the sliding variables studied and their influence was closely related to the development of a transfer film during the run-in state. If the transfer film developed during initial sliding, the coefficient of friction increased and wear rate decreased. The wear rate in the run-in state increased with the increase in initial counterface roughness and there was an optimal counterface roughness of 0.06 m Ra for minimum steady state wear rate. A higher applied load led to a higher wear rate in the run-in state but that was not the case with steady state wear rate.     

Effect of Nitrogen Doping on Sliding Wear Behaviour of Stainless Steel Coatings

Nitrogen-doped austenitic stainless steel coatings have been deposited onto a mild steel substrate by the magnetron sputtering technique, with the purpose to enhance the tribologica1 and chemical properties of the steel. The resultant coatings with different degrees of nitrogen doping have been characterised by X-ray diffraction, scanning electron microscopy and nanoindentation. Dry sliding friction and wear tests have been conducted to investigate the tribological behaviour of the coating-substrate systems. The results show that nitrogen doping stabilises and expands the austenite lattices, which leads to a significant hardening effect in the coating without formation of harmful nitride compound phases. With an appropriate amount of nitrogen doping, the coating exhibits much enhanced sliding wear resistance. However, excessive nitrogen doping leads to the deterioration in tribological performance due to coating embrittlement and reduced coating-substrate integrity.     

Effect of Sintering Temperature and Atmosphere on Nonlubricated Sliding Wear of Nano-Yttria-Dispersed and Yttria-Free Duplex and Ferritic Stainless Steel Fabricated by Powder Metallurgy

The nonlubricated sliding wear behavior of nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel against a diamond tip was studied. The stainless steel samples were fabricated by a conventional powder metallurgy route in which nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel powders were cold compacted and then conventionally sintered at either 1000, 1200, or 1400°C in an argon atmosphere. For comparison, another set of samples was sintered at 1000°C in a nitrogen atmosphere. The wear behavior of sintered stainless steel samples against a diamond indenter was investigated using a pin-on-disc apparatus at 10 and 20 N loads and at a constant speed of 0.0041 m/s. It is proposed that yttria-dispersed stainless steels showed higher wear resistance compared to yttria-free stainless steel due to their improved hardness and density. Stainless steel sintered in a nitrogen atmosphere exhibited better wear resistance than those sintered in an argon atmosphere due to the formation of hard and brittle Cr₂N. The wear mechanisms of stainless steels against diamond were found to be mainly abrasive and oxidative. Semiquantitative analysis of the worn surfaces and wear debris confirmed the occurrence of oxidation processes during wear.     

Transition of Mild Wear to Severe Wear in Oxidative Wear of H21 Steel

Under atmospheric conditions at 400 °C, we studied the wear mechanism of H21 steel with different tempering states as a function of normal load. Typical oxidative wear was identified by X-ray diffraction patterns with predominant tribo-oxides of Fe₃O₄ and Fe₂O₃. Under loads of 50–100 N, mild oxidative wear prevailed for all samples, such that the wear losses of H21 steel with various tempering states showed no significant differences with characteristics of a slight plastic deformation of the substrate and single-layer oxide. In this case, the wear rate was lower, and the tribo-oxide was decisive factor in determining wear rate. Under loads of 150–200 N, the transition of mild wear to severe wear occurred in H21 steel and was characterized by: (1) a significant difference of wear losses for steel with various tempering states; (2) wear loss that started to increase faster and reached a relatively high level; (3) the appearance of significant plastic deformation in the oxide underneath the substrate and multi-layer tribo-oxide. Under a load of 200 N for the steel tempered at 700 °C, plastic extrusion prevailed with a mixed metal-oxide layer.     

Effect of Nickel on the Wear Rate of Fe‐Cr‐C‐Ni Steel Under Sliding Friction

Under sliding friction, nickel (0.3–4.2 wt.%) alloyed with chromium steel (1.2 wt.% carbon; 15 wt.% chromium) exerts a fundamental influence upon the initial structure of the steel and the phase composition and structure of the near‐surface friction layers. The minimum wear of the steel occurs when there is a dynamic equilibrium between the dislocation densities in the α‐ and γ‐phases and a ratio between the γ‐ and α‐phases of 50:50 for steels after quenching and 25:75 for steels after tempering in the near‐surface friction layers.     

High-Temperature Friction and Wear of Boron Steel and Tool Steel in Open and Closed Tribosystems

More and more components in automotive, material processing, and mining industries are operating under harsh conditions involving high temperatures and high contact pressures. Tribotesting for such applications is done using both open (one surface meeting a fresh countersurface) and closed (one surface follows the same track on the countersurface) test configurations. In order to enable development of new materials and processes intended for such conditions, there is a need for better understanding pertaining to tribological phenomena occurring under these different test configurations.

In this work, friction and wear characteristics of quenched and tempered tool steel sliding against boron steel (22MnB5) have been studied. The experiments were conducted using a specially designed hot strip tribometer (HST) under dry conditions at room temperature and 400°C in open as well as closed configurations. Scanning electron microscopy/energy-dispersive spectroscopy, and X-ray techniques were carried out to analyze the worn surfaces. Additionally, the results from the closed test configuration were compared to previous tests carried out with the same materials and parameters using a pin-on-disk (POD) test rig. The results have shown that wear was reduced at higher temperatures as well as with repeated sliding on the same contacting surfaces (i.e., closed configuration) compared to those with an open configuration. A good correlation of wear mechanisms and coefficient of friction between closed configuration tests and those carried out with the POD test rig were observed especially at 400°C.     

钢轨滚动磨损性能试验研究

在JD-1型轮轨摩擦试验机上研究了轴重与曲线半径对钢轨滚动磨损性能的影响。结果表明：轴重与曲线半径是影响钢轨磨损的主要因素。试样磨损量随着载荷的增加而增加,也随着曲线半径的减小而增加;试样表面磨损形貌随着载荷与曲线半径的改变而表现出不同的变化,其中大载荷和小曲线半径试验使钢轨试样磨损程度严重,表面容易产生较明显的塑性形变以及龟裂现象;制动力条件下滚动试样磨损更为严重。     

青铜-石墨热喷涂层在干摩擦和水润滑条件下的摩擦磨损性能

在MM-200摩擦磨损试验机上研究了青铜-石墨热喷涂层在干摩擦和水润滑条件下的摩擦磨损性能,采用扫描电镜(SEM)对磨损表面形貌进行了观测和采用X射线能谱分析(XPS)分析了涂层成分。结果表明,在水润滑条件下涂层摩擦因数和磨损率均低于干摩擦条件下;在水润滑条件下磨损机制为轻微磨粒磨损和犁削磨损,在干摩擦下主要是较为严重的粘着磨损和犁削。这是由于水润滑降低了摩擦副界面温度,提高了石墨润滑膜的韧性,改善了润滑效果,从而阻止了粘着磨损的发生,水还促进了钢偶件表面致密氧化膜的形成,从而减轻磨损。因此水润滑对涂层磨损性能有较大影响。     

新型CL60钢地铁车轮摩擦磨损试验研究

为了提高地铁车轮的服役性能,对车轮用CL60钢材料中Si、Mn、Cr等元素的质量分数进行重新设计和优化,研发新型CL60钢地铁车轮,通过GPM-60摩擦磨损试验机模拟轮轨磨损试验,研究原CL60钢车轮与新型CL60钢车轮在实验室条件下的磨损特性。基于赫兹模拟准则设计计算了模拟试验采用的轮轨试样尺寸、施加的载荷和转速;通过不同载荷工况下的摩擦磨损试验和轮轨材料微观组织分析,研究2种轮-轨试样的磨损量、磨损率、塑性变形及表面形貌的变化规律及特征,对新型CL60钢车轮的使用性能进行评价。结果表明：与原CL60钢车轮相比,在不同载荷下新型CL60钢车轮试样磨损量、轮-轨试样总磨损量、磨损率及摩擦表面塑性变形层厚度均大大降低,其抗磨损性能和塑性变形能力得到了改善。     

Wear mechanisms in deep drawing of carbon steel – correlation to laboratory testing

In the present research, a comparison of worn surface morphologies and wear mechanisms observed for worn deep drawing dies and sheets from the automotive car body manufacturing and worn surfaces obtained by a slider‐on‐flat‐surface (SOFS) tribometer has been carried out. Abrasion and adhesion were identified as the main surface damage mechanisms on the investigated dies and sheets. Comparison of the results obtained in laboratory testing using the SOFS tribometer showed that the test method properly simulates the tribological conditions occurring in actual sheet metal forming operations. Copyright © 2007 John Wiley & Sons, Ltd.     

超高速滑动电接触CuCrZr合金轨道表面磨损机制及电接触性能

电磁轨道发射具有典型超高速滑动电接触特性（出口速度大于等于2 000 m/s）,电磁轨道表面会发生磨损。为研究轨道表面磨损状态与接触电阻之间关系,通过开展电磁轨道发射试验,研究发射后的CuCrZr轨道表面沉积层的形成与磨损机制,揭示枢轨间静态接触电阻的演变规律,总结沉积层的形成与接触电阻的关联关系。结果表明：沿着发射方向,轨道表面沉积层覆盖面积逐渐增大,沉积层的形成机制由摩擦材料转移变为电枢表面熔化飞溅,表面磨损特征由机械磨损向电气磨损转变;由于轨道不同位置沉积层形成原因不同,导致表面粗糙度分布不一致,枢轨间静态接触电阻随接触沉积层形貌特征改变呈现上升、下降及波动3个变化阶段;并且枢轨间静态接触电阻随着接触压力的增大而减小。研究成果对电磁轨道发射装备的研究及发射动力学研究具有理论价值。     

钢纤维和氧化铁粉含量对半金属摩擦材料摩擦磨损性能的影响

半金属摩擦材料中的钢纤维、氧化铁粉是重要的增强组分和调节剂。研究钢纤维含量和氧化铁粉含量对半金属摩擦材料摩擦磨损性能的影响,以获得较佳的配比。研究结果表明:随钢纤维含量增加,摩擦因数增加,且摩擦因数的稳定性和抗热衰退能力提高;但随钢纤维含量的增加,磨损率也随之增加;当钢纤维质量分数为20%时,摩擦材料的摩擦因数较平稳,350℃时几乎没有明显的热衰退,磨损率也较低。氧化铁粉的含量对摩擦因数影响不大,但可改善摩擦材料的自润滑性和抗高温热衰退性;但过多的氧化铁粉含量,导致磨损率增大,特别是高温时更为明显,从摩擦因数的稳定性与磨损率两方面综合考虑,氧化铁粉质量分数为5%时摩擦材料具有较好的摩擦磨损性能。     

空调滑片用低成本GDL-4高速钢软氮化后耐磨性能的对比

空调压缩机滑片对制造材料的红硬性和耐磨损性能有较高的要求,为此生产中通常采用表面氮化处理工艺。本文对研发的低成本GDL-4高速钢与M2高速钢、11Cr17不锈钢试样进行相同的软氮化工艺处理,在300N载荷下进行摩擦磨损实验对比其耐磨性,结果表明:在相同的常规软氮化工艺条件下,GDL-4钢的耐磨性能好于M2钢和11Cr17不锈钢,检测发现氮化后钢表层硬度梯度的分布对耐磨性有重要的影响。     

稀土Y对H13钢表面TiN薄膜高温摩擦磨损性能的影响

利用离子镀技术,在H13钢基体上制备了TiN薄膜,并且添加稀土元素Y作为过渡层处理,进行TiN系列薄膜高温摩擦磨损性能的对比试验。结果表明,采取适当的镀膜工艺添加稀土元素Y后,TiN薄膜处理的试样的摩擦因数由0.163减小到0.129,磨损率也由0.88‰降低到0.09‰。试样表面的磨损形貌分析结果表明,TiN薄膜处理的试样表面有大片的粘着磨损破裂区和由磨粒磨损引起的较深犁沟;TiYN薄膜处理的试样则保持了较平顺的磨损表面,没有明显的粘着磨损破裂区和磨粒磨损形成的犁沟。稀土元素Y的加入,进一步改善了TiN薄膜的高温摩擦磨损性能,提高了H13热作模具的抗磨减摩效果。