高温下位移幅值对TC4合金磨损性能的影响

钛合金的微动磨损会加速裂纹的形成与扩展,导致其构件提前失效。利用摩擦磨损试验机考察TC4合金在300和500℃温度下的微动磨损行为,利用扫描电子显微镜和激光共聚焦显微镜对磨痕轮廓及磨痕表面进行分析,探讨在300和500℃温度下TC4合金在不同位移幅值作用下的微动磨损机制。实验结果表明：高温条件下,试样平均摩擦因数和磨损率随位移幅值的增加呈现先增大后减小的趋势;两种高温环境中,小位移幅值时,微动运行区域为部分滑移区,主要损伤机制为黏着磨损和氧化磨损;位移幅值为100μm时,微动运行区域为混合滑移区,主要磨损机制为氧化磨损、剥层磨损及塑性变形;大位移幅值时,微动运行区域为完全滑移区,主要磨损机制为磨粒磨损和疲劳磨损。对比300和500℃条件下磨损结果,表明温度越高TC4合金耐磨性能越好,这主要是由于摩擦生成的氧化物TiO₂和Fe₂O₃对磨损表面具有保护作用。     

微滑动条件下PS304涂层与Si_3N_4配副的摩擦学性能研究

利用大气等离子喷涂在不锈钢表面制备PS304高温自润滑涂层。采用X射线衍射仪、扫描电子显微镜表征涂层的组成和结构;采用SRV微动摩擦磨损实验机研究PS304涂层和Si3N4摩擦副从室温到800℃的摩擦磨损性能;用扫描电子显微镜观察涂层和对偶球的磨损形貌,并分析涂层在室温和600℃的摩擦磨损机制。结果表明,常温下,涂层的摩擦因数和磨损率均较高,磨损表面伴随脆性断裂迹象,主要表现为磨粒磨损机制。在600℃下,涂层表现最低的摩擦因数和最小磨损率,其表面形成润滑膜并发生一定的塑性变形,磨损机制主要为黏着磨损。     

温度对不同运行工况下Zr-4锆合金微动磨损行为的影响

采用高温微动磨损试验机对Zr-4合金管进行切向微动磨损试验，通过改变法向载荷研究了试验温度(25,100,200,325℃)对不同运行工况(完全滑移区和部分滑移区)下微动磨损行为的影响。结果表明：在相同试验温度下完全滑移区的摩擦因数高于部分滑移区，不同运行工况下200,325℃时的摩擦因数更早达到稳定状态。在完全滑移区，合金的磨损机制包括磨粒磨损、氧化磨损和剥层，温度的升高对合金微动磨损程度的影响较大，325℃时的微动磨损程度最大；而在部分滑移区，磨损机制包括剥层、黏着磨损和氧化磨损，试验温度的升高对微动磨损程度的影响很小。在相同试验温度下，部分滑移区的微动磨损量远低于完全滑移区；试验温度的升高对完全滑移区微动磨损量的影响较明显，而对部分滑移区的影响不大。     

WC-10Co-4Cr涂层高温微动磨损特性

为研究WC-10Co-4Cr涂层的高温微动磨损性能和微动磨损机制,采用超音速火焰喷涂技术在Inconel690合金表面制备WC-10Co-4Cr涂层。使用PLINT电液伺服高温微动试验机,在室温25℃至高温300℃大气气氛条件下,选择法向载荷100 N、位移幅值200μm、频率2 Hz、循环次数3×10~4次,进行微动磨损特性试验,通过扫描电子显微镜、双模式轮廓仪和三维共聚焦显微镜等仪器对磨痕进行分析研究。结果表明:涂层组织呈层状叠加的两相分布,致密、孔隙率低,涂层与基体结合紧密,显微硬度为HV810.82,是基体的3.3倍;在法向载荷和位移幅值一定时,随着试验温度的升高WC-10Co-4Cr涂层的摩擦因数增大,且磨损加剧;温度高于250℃条件下,WC-10Co-4Cr涂层发生严重磨损;WC-10Co-4Cr涂层的高温微动磨损机制主要表现为黏着磨损、氧化和剥层的共同作用。     

不同滑动条件下 Ｈ１３ 钢的高温磨损行为

采用销-盘式高温摩擦磨损试验机，对H13钢常规淬火与回火处理试样进行高温磨损实验，研究H13钢在400~600 ℃、50~150 N、50和100 r/min条件下的摩擦磨损性能。采用XRD、SEM、EDS、显微硬度计对H13钢磨面、磨损截面的结构、形貌、成分及硬度进行分析，并探讨其磨损机制。结果表明：在不同实验条件下H13钢的磨损率均随温度升高先降低后升高，其中500 ℃的磨损率最低，在低转速下600 ℃的磨损率低于400 ℃，而在高转速和较高载荷下则相反；在低转速下的磨损率随载荷的增加先升高后降低，而在高转速下的磨损率单调升高，且在600 ℃、150 N条件下发生严重磨损，而在其他滑动条件下均为轻微磨损；H13钢在高温下磨面会形成氧化物，但在高转速不利于磨面上氧化物的生成，因而生成等量的氧化物需要更高的温度；中低温下氧化物的生成起到减磨作用，磨损率下降，而在高温下H13钢基体发生回复、再结晶，力学性能较差，在高载高速下导致基体发生严重塑性挤出，轻微氧化磨损转变为严重氧化磨损。     

不同基体CrN/CrCN多层涂层海水环境摩擦学性能研究*

为研究不同基体材料对CrN/CrCN多层涂层在海水环境下摩擦学性能的影响,采用多弧离子镀技术在H65铜合金、TC4钛合金和316L不锈钢基体上沉积CrN和CrN/CrCN多层复合涂层,通过XRD、SEM等技术对涂层的结构进行表征,通过结合力、硬度测试和摩擦磨损试验分析涂层在大气环境和海水环境下的力学性能和摩擦学性能。结果表明:CrN/CrCN多层涂层的内应力相对于CrN明显减小,且硬度相对CrN涂层较高;TC4钛合金为基体的涂层结合力较好且涂层硬度较高;在海水环境下涂层的摩擦因数相对于大气环境都有较大幅度下降,其中,以TC4钛合金和316L不锈钢为基体的涂层摩擦因数较小;以H65铜合金为基体的2种涂层在海水中的磨损率高于大气中,而以TC4合金、316L不锈钢为基体的CrN/CrCN多层涂层在海水环境下的磨损率低于大气环境;TC4钛合金为基体的CrN/CrCN多层涂层在海水环境下具有最低的磨损率,表明TC4钛合金更适合作为海水环境下CrN/CrCN多层涂层耐磨的基体材料。     

Ti6Al4V合金在Saline溶液中的微动腐蚀特性

采用液压高精度微动试验机,做了Ti6A l4V/Si3N4摩擦副在干态、蒸馏水和Saline溶液等3种介质中的微动腐蚀试验,用激光共焦扫描显微镜(LCSM)观察了磨痕表面形貌并测量了磨损体积。结果表明:蒸馏水和Saline溶液改变了微动运行区域;空气中的摩擦因数与磨损体积最大,Saline溶液中最小,3种介质中的摩擦因数与磨损体积均随位移增加而增加;载荷增加时,磨损体积增大而摩擦因数减小;较大位移时,腐蚀与磨损交互作用显著地加速了Ti6A l4V的材料流失;微动损伤主要表现为剥落与磨粒磨损共同作用。     

水膜及油水混合膜对GCr15钢微动磨损行为的影响

在室温(20~25℃)及超湿大气环境(RH 95%~105%),载荷50、100、150 N,位移幅值80、150、300μm,频率10 Hz,水汽和润滑油组合介质中,做了GCr15钢的微动磨损试验。结果显示:与干态比较,水膜及油水混合膜使微动摩擦因数和磨损率显著下降,微动损伤减轻;油水混合膜的作用优于水膜。结合微动磨痕形貌观察讨论并建立了水膜及油水混合膜结构模型。     

Mg97Zn1Y2镁合金的高温磨损行为

对Mg97Zn1Y2合金的室温磨损行为已有研究,但是缺乏高温磨损研究,探究该合金高温磨损行为是非常必要的。采用MG-2000型销-盘磨损试验机对Mg97Zn1Y2合金进行磨损试验,试验温度范围为20~200℃,加载范围为20~320 N,探究不同温度以及载荷对Mg97Zn1Y2合金磨损行为的影响。根据试验数据绘制不同温度下的磨损率曲线;应用SEM观察磨损表面形貌,应用EDS分析磨损表面的化学成分,划分磨损区间。结果表明：随着温度的升高,Mg97Zn1Y2合金的磨损率随载荷的增加而上升得更加显著,磨损行为可以分为轻微磨损和严重磨损两个阶段：轻微磨损阶段的磨损机制为：磨粒磨损、剥层磨损、氧化磨损;严重磨损阶段为严重的塑性变形和表面熔化。绘制了磨损机制转变图,划分该合金的安全工作区间,为该合金在高温下的摩擦学应用提供有益参考。     

载荷对MoSi_2/Si_3N_4配对副高温磨损性能的影响

在XP-5高温摩擦磨损试验机上考察了MoSi2/Si3N4配对副在1 000 ℃、0.126 m/s滑动速度以及不同载荷条件下的摩擦磨损性能,通过扫描电子显微镜(SEM)和X射线衍射仪(XRD)对MoSi2/Si3N4配对副磨损表面进行了分析.结果表明:MoSi2/Si3N4配对副在1 000 ℃高温滑动时,MoSi2的摩擦因数随载荷的增大而降低,其磨损率则呈上升的趋势;随着载荷的增加,MoSi2的磨损机制依次表现为氧化、粘着、研磨和疲劳断裂.Si3N4盘的主要磨损形式为粘着和氧化,氧化增重引起其磨损率为负值.     

不同润滑介质下GCr15/45#钢摩擦磨损特性的研究

利用DELTALAB-NENEDS20型高精度液压式微动试验机在干摩擦、水润滑和油润滑等条件下，对GCr15／45#钢进行了微动磨损实验，研究了润滑条件对GCr15／45#钢对摩时的摩擦学性能的影响，并利用激光共焦显微镜对45#钢的磨损表面进行了观察和分析。结果表明润滑介质可以降低摩擦副摩擦因数和45#钢的磨损量；材料的磨损机制也随着润滑条件的不同发生了相应的变化。     

Friction and wear of Inconel 690 for steam generator tube in elevated temperature water under fretting condition

Recently, material of Inconel 690TT (thermal treatment) for the steam generator tubes in a nuclear power plant was substituted for the existing material of Inconel 600HTMA (high temperature mill-annealing). Inconel 690TT has more chromium than Inconel 600HTMA in order to improve the corrosion resistance. In this study, to evaluate the friction and wear characteristics of Inconel 690TT under fretting condition, the fretting tests as well as sliding tests were carried out in air and in elevated temperature water environment, respectively. Fretting tests of the cross-cylinder type were done under various applied normal loads, and sliding tests of pin-on-disk type were also carried out to compare with the results of the fretting test. In summary, the results of the fretting tests correlated with the results of the sliding tests. The wear mechanism of Inconel 690TT in air was delamination wear and the mechanism in water was affected by micro-pitting. Also, it was found that the fretting wear coefficients in water were increased with increase in the temperature of water.     

Tribological characterisation of a‐C:H coatings at room temperature: Effect of counterbody material

Metal‐free amorphous carbon (a‐C:H) coatings with 15% hydrogen were deposited on bearing steel surfaces. The friction and wear performance of these specimens was characterised in oscillating sliding tests with a ball‐on‐flat geometry. Balls of four ceramic and four metallic materials were investigated in tests at room temperature. Special attention was paid to the effect of moisture by testing in dry, normal, and moist air. The effect of water vapour on the friction and wear of the a‐C:H coatings was quite different for the different counterbody materials. The wear was in all cases very low, with a coefficient of wear below 10⁻⁷ mm³/N m for most cases. The coefficient of friction was also very low, between 0.04 and 0.12 for most of the tests. The smallest wear and friction coefficients were found for oxide ceramics, while during tests against SiC and Si₃N₄ the coating was worn through during the test. The effects of counterbody material and the humidity of the surrounding air are discussed in terms of friction and wear mechanisms.     

316不锈钢材料的统计热疲劳模型

通过对316不锈钢材料在450℃,600℃和700℃中温环境应力控制下的低周疲劳试验,得到有实际意义的试验结果,对这些试验结果进行分析和研究,得出316不锈钢材料在中温环境和应力控制下的低周热疲劳行为,并且提出一个低周热疲劳寿命预测模型。在所建立的低周热疲劳寿命模型中,Manson通用斜率方程被用于疲劳寿命与拉伸性能的试验整合。通过对疲劳试验数据与不同的数学模型进行的拟合以建立温度和其他参数之间的函数关系,从而对316不锈钢材料在中温低周疲劳环境下进行寿命预测,为以后的寿命评估模型提供依据。     

Influence of temperature on tribological behaviour of ionic liquids as lubricants and lubricant additives

Ionic liquids are low‐melting‐point salts composed entirely of ions, and many of them are liquids at room temperature. In recent years, studies have indicated that they might be good candidates for lubricants, either in neat or additive form. In this work, a sulfate‐based ionic liquid with a pyrollidinium cation was studied as neat lubricant and as additive for glycerol in lubrication of steel–steel contacts. Glycerol was chosen as the base oil because of its high polarity, which allows full miscibility with polar ionic liquids. Tests were performed on an oscillating friction and wear tribometer. The coefficients of friction and wear were measured. The tests were run at room temperature, 50 °C, 100 °C and 150 °C. By using profilometry, optical microscopy, scanning electron microscope and atomic force microscopy (AFM) analyses, it was shown that the ionic liquid plays an important role in the friction and wear reduction, as well as in the smoothening of the worn surface. Copyright © 2013 John Wiley & Sons, Ltd.     

Wear behaviour of forging steels with different microstructure during dry sliding

Sliding wear behaviour of two types medium carbon microalloyed steels containing various microstructures was investigated on a 320 mesh SiC paper at a sliding speed of 0.33 m/s with a load of 6 N and sliding duration of 4 min under dry sliding conditions (the sliding distance, 80 m). The experimental results showed that the different microstructures cause a great influence on the wear resistance performance of the steels. Water quenched samples with martensite structure have the highest hardness and wear resistance performance. That is because, water cooled samples contained higher amount of carbon in the solid solution. On the other hand, air or sand cooling from forging temperature results in a decrement of hardness and wear resistance in steel-1 and steel-2. However, air cooled samples showed slightly higher wear resistance than sand cooled samples due to finer grain sizes and the larger pearlite and/or precipitation contributions.     

Friction and Wear of Metals in Gases Up to 600 C

Apparatus is described for measuring friction and wear in controlled atmospheres. A comparison is made of the room temperature behavior of copper, mild steel and brass, rubbed against a hardened tool steel, in four environments—vacuum (10^?3 mm Hg), dry helium, dry carbon dioxide, and dry air. The effect of varying the water vapor content in air is also discussed.

The initial selection of rubbing pairs for service at elevated temperatures is gaseous environments under unlubricated conditions, is based on their long-term resistance to corrosion and their ability to give low wear rates. In general, therefore, the materials must be hard. Several alloys having chromium contents of between 1% and 30%, and hardness values in the range 200–1000 vpn have been investigated. These included two low-chromium nitrided steels, a tungsten-chromium tool steel and a series of four Co-Cr-W alloys. Specific wear rates and friction coefficients varied markedly with temperature, and values in the ranges 10^?13–10^?8 cm³/cm kg and 0.1–0.8, respectively, were obtained in both dry carbon dioxide and dry helium. Lowest wear rates were observed with the nitrided steels. The diverse characteristics observed are discussed on the basis of current theories of adhesive wear.     

Research on oxidation wear mechanism of the cast steels

The uni-directional pin-on-disk wear tests were performed in elevated-temperature air at 400 °C for the Cr–Mo–V cast steels with different compositions. Morphology, composition and structure of worn surfaces, oxidation films and matrix were examined using SEM, EDS, XRD and TEM. The relations between oxidation wear rate and matrix were studied. The mechanism of wear was clarified. Under elevated-temperature air at 400 °C, typical oxidation wear was presented in the cast steels. Oxidation of worn surface and fatigue delamination of oxide film proceed alternatively during sliding. As there are not coarse second phases in steel, oxide film is main factor in determining wear rate, which conforms to Quinn's oxidation wear theory. In this case, delamination of oxide film was found to take place inside oxide film or at interface of matrix and oxide film. This is classified as mild oxidation wear with lower wear rate. As coarse second phases exist in steel, the wear rate is strongly dependant on microstructures of matrix. In this case, oxide film delaminates from the inside of matrix under oxide film. This is classified as severe wear with high wear rate.     

Tribological Property of Selective Laser Melting–Processed 316L Stainless Steel against Filled PEEK under Water Lubrication

Abstract

As a 3D printing technology, selective laser melting has remarkable advantages such as high processing flexibility, high material utilization, and short production cycle. The applications of selective laser melting technology in industry have become quite extensive. There are many tribological studies on selective laser melting materials, but few based on water lubrication (Zhu, et al., Journal of Zhejiang University-Science A, 19(2), pp 95–110). In this article, the tribological properties of 316L stainless steel processed by selective laser melting and traditional methods have been studied under water lubrication. Polyether ether ketone (PEEK) filled with carbon fiber (CF)/polytetrafluoroethylene (PTFE)/graphite was selected as the counterpart. 316L stainless steel and PEEK are a tribopair commonly used in water hydraulics. This study is of great significance to the application of selective laser melting material of tribopairs in water hydraulics. Friction and wear tests were carried out on a pin-on-disc contact test apparatus under different operating conditions. The friction coefficient, specific wear coefficient, scanning electron microscopy (SEM) of the worn surface, and energy-dispersive spectroscopy (EDS) of the surface adhesions of the three tribopairs were measured and compared. The results revealed that the friction coefficient of the selective laser melting (SLM) 316L stainless steel was significantly higher than that of traditionally processed (TP) 316L stainless steel, which might be caused by the pores on the surface of SLM 316L stainless steel. Adhesion and cutting on the surface of SLM 316L stainless steel were also more serious, resulting in a higher specific wear coefficient of its counterpart PEEK composite compared to PEEK composite against TP 316L stainless steel.