Tribological behavior of CrN-coated Cr-Mo-V steels used as die materials

DIN 1.2343 and 1.2367 steels are commonly used as die materials in aluminum extrusion, and single/duplex/multi-coatings enhance their surface properties. The design of an appropriate substrate/coating system is important for improving the tribological performance of these steels under service conditions because the load-carrying capacity of the system can be increased by decreasing the plastic deformation of the substrate. In this study, the tribological behavior of CrN-coated Cr-Mo-V steels (DIN 1.2343, 1.2367, and 1.2999 grades) was investigated using different setups and tribological pairs at room and elevated temperatures. The aim of this study was to reveal the wear resistance of a suggested system (1.2999/CrN) not yet studied and to understand both the wear and the failure characteristics of coated systems. The results showed that (i) among the steels studied, the DIN 1.2999 grade steel exhibited the lowest friction coefficient because it had the highest load-carrying capacity as a result of secondary hardening at elevated temperatures; (ii) at room temperature, both abrasive tracks and adhesive layers were observed on the worn surfaces; and (iii) a combination of chemical reactions and progressive oxidation caused aluminum adhesion on the worn surface, and the detachment of droplets and microcracking were the characteristic damage mechanisms at high temperatures.     

Tribological behaviors of some polymeric materials in sea water

Ocean tribology, a new research field of tribology, is being established and developing. The investigation on the tribology in sea water has important significance to ocean exploitation. In this paper, the tribological behaviors of UHMWPE, PTFE as well as Ekonol/PTFE, graphite/PTFE and CF/PTFE sliding against GCr15 steel and Ni-Cr-WC alloy in sea water were investigated, and compared with those in pure water. Results show that the main factors that affect the tribological behaviors of five polymeric materials in sea water are the corrosive effect and lubricating effect of sea water. When polymeric materials sliding against GCr15 in sea water, owing to serious corrosion of counterface by sea water, the surface roughness of the counterface increases largely. As a result, the lubricating effect of medium decreases sharply and the plowing effect of counterface increases greatly. So the friction coefficients and wear rates of five materials sliding against GCr15 in sea water are much larger than those under other conditions. Such wear model, depending on the corrosion of counterface by medium, can be called indirect corrosive wear. Under other three conditions, owing to the more superior lubricating effect of sea water than pure water and the better wettability of Ni-Cr-WC than GCr15, the friction coefficients and wear rates of five materials increase in the following order： sliding against Ni-Cr-WC in sea water 〈 sliding against Ni-Cr-WC in pure water 〈 sliding against GCr15 in pure water. Moreover, compared with other materials, CF/PTFE is the one with more superior plowing and wear resistance in pure and sea water, which is a potential frictional material well suitable for pure and sea water lubrication.     

Effect of different atmospheres on dry friction behavior of steel sliding against brass at high speed

The atmosphere components have an influence on tribological behaviors of tribo-pairs. Through changing the atmosphere component, the effect of atmosphere component on the tribological behaviors of CrNiMo steel against brass at high sliding velocity was investigated. The wear test was carried out on a high-speed friction and wear test rig whose test atmosphere could be controlled. The tests were performed at four sliding velocities （30, 40, 50, 60 m/s）, one contact pressure （1.33 MPa） and two atmosphere components （N2 or O2）. The morphologies of the worn surfaces of various pins were observed with a scanning electron microscope. The chemical compositions of the surfaces and subsurfaces for steels were determined with an energy dispersion spectroscopy. The results showed that the wear rate of the steel pins were low all the time with the sliding velocity increasing in oxygen atmosphere, and that the wear rate of the steel pin in nitrogen atmosphere was higher than that of the steel pin in oxygen atmosphere. It was found that the thin and compact oxidation layer formed on the worn surface of the steel in oxygen atmosphere played a key role in wear resistance. However, the wear rate of the steel pin increased rapidly with the sliding velocity increasing in nitrogen atmosphere, which was attributed to the thick and loose surface layer formed on the worn surface of the steel.     

分子有序膜及其摩擦学行为研究进展

介绍了LB膜、自组装单分子膜(SAMs)、分子沉积(MD)膜等分子有序膜的基本概念和薄膜结构、厚度、性质以及微摩擦学行为的表征技术,并指出LB膜层问是物理吸附,热力学稳定性差;SAMs以化学键为驱动力,重现性较差;而分子沉积膜具有成膜不受基底形状和大小限制等优点,决定了它在微电子器件润滑方面具有更大的应用前景．在分子有序膜的摩擦学研究方面,着重介绍了分子有序膜本身结构(如物质种类、组成、分子链长、末端基团等)和外部条件(如法向载荷、扫描速率、相对湿度等)对摩擦学行为的影响．最后,提出了本领域需要关注的一些问题。     

掺铬类石墨薄膜摩擦学性能研究

采用非平衡磁控溅射离子镀技术,以电流控制方式在高速钢和硅基底上制备了不同C r含量的C/C r类石墨薄膜,测量了类石墨膜的显微硬度、膜基结合强度、摩擦系数和比磨损率,分析了薄膜的相结构,观察了薄膜的表面和断面形貌。结果表明:所制备的类石墨薄膜随C r含量的增高,硬度逐渐降低,结合强度先增后降,摩擦系数和比磨损率则先降后升;类石墨膜是含有多种纳米晶的非晶结构;金属元素C r含量影响了类石墨碳膜的表面形貌和组织结构。当C r含量在0.5%~2.5%时,薄膜表面光滑而结构致密,摩擦系数小且比磨损率低,膜基结合强度高,具有良好减摩耐磨性能。     

TaAgN复合膜显微结构、力学性能和摩擦性能的研究

采用非平衡反应磁控溅射法制备了TaAgN复合膜。利用X射线衍射仪、CSM纳米压痕测试仪和摩擦磨损测试了复合膜的显微结构、力学性能和摩擦性能。结果显示,TaAgN复合膜由面心立方结构的TaN相和底心斜方结构的Ta₄N相组成。随着Ag靶功率的增加,硬度H、弹性模量E、弹性恢复W_e和H³/E²值均呈先升高后降低的趋势,最大值分别为34 GPa,394 GPa,57%和250 MPa。随着Ag靶功率的增加,TaAgN复合膜室温下的平均摩擦因数呈降低趋势。当Ag靶功率为25 W时,随着温度的升高,TaAgN复合膜的平均摩擦因数逐渐减小。     

微米级二硫化钼作为添加剂的润滑油性能研究

将表面改性后的微米级二硫化钼添加至基础油中,利用MRS-10W型和M-2000型试验机,对所制备润滑油的摩擦学性能进行测定.结果表明,基础油中添加含量为1.5%的微米级二硫化钼后,润滑油的最大无卡咬载荷提高了15.5%,摩擦副之间的摩擦系数降低了33.1%,磨损量减少了43.5%.     

铁基金属陶瓷复合材料摩擦学特性研究

研制出铁基金属陶瓷复合材料 ,并对该材料的摩擦学特性和磨损机制进行了研究 ,提出了一种铁基金属陶瓷复合材料摩擦系数半定量分析的力学模型 .该模型解释了摩擦系数随制动比压和制动速度的变化关系     

Fe_xSi_y改性C/C-SiC制动材料的制备及其性能

以针刺整体炭毡为预制体,采用化学气相渗透法(CVI)增密制备C/C多孔体,采用反应熔体浸渗法(RMI),将Fe与Si同时熔渗进C/C坯体中制备FexSiy改性C/C-SiC复合材料。研究FexSiy改性C/C-SiC复合材料的组织结构、力学性能和摩擦磨损性能。研究结果表明:硅铁化合物被SiC基体包围填充于C/C坯体孔隙中;FexSiy改性C/C-SiC复合材料的弯曲强度为189.65 MPa,垂直和平行摩擦面的压缩性能分别为296.93 MPa和201.32 MPa;分别采用30Cr钢和自身材料作对偶时,FexSiy改性C/C-SiC复合材料的平均摩擦因数均为0.24左右,线磨损均小于3.5μm.面-1.次-1,但与铬钢对摩静系数明显增大,而与自身对摩制动曲线出现明显翘尾现象,其摩擦磨损过程是由磨粒磨损、黏着磨损和氧化磨损相互作用的结果。     

泡沫铝合金孔隙率对泡沫铝合金/聚甲醛互穿复合材料的影响

使用硅烷偶联剂KH570对孔隙率不同的泡沫铝合金进行表面改性后,通过注塑成型法制备了聚甲醛/泡沫铝合金互穿复合材料。研究了改性后泡沫铝合金表面的红外结构、泡沫铝合金/聚甲醛互穿复合材料的力学性能和摩擦学性能以及泡沫铝合金/聚甲醛互穿复合材料的磨损表面。研究结果表明,硅烷偶联剂KH570成功接枝到了泡沫铝合金的表面;复合材料的弯曲强度和压缩强度随着泡沫铝合金孔隙率的降低而升高;而复合材料的摩擦学性能随着泡沫铝合金孔隙率的增加而降低。