Al2O3—TiB2陶瓷刀具材料的高温氧化及其对刀具耐磨性能的影响

研究了Ａｌ２Ｏ３－ＴｉＢ２陶瓷刀具材料在１０００℃下的氧化行为，用ＸＲＤ、ＳＥＭ分析了氧化后的相组成及显微结构。结果表明：Ａｌ２Ｏ３－ＴｉＢ２陶瓷材料在１０００℃空气中氧化增重符合抛物线规律；随ＴｉＢ２含量的增加，该材料的抗氧化能力下降。     

石匣小流域坡地水土流失监测系统的建立及应用

以石匣小流域为坡地水土流失监测试点,以遥感及地理信息系统技术为手段,以坡地径流小区定位观测为依据,建立石匣小流域坡地水土流失监测系统,定位、定性、定量监测各种坡地类型的水土流失量、污染物流失量,为水土流失监测预报提供数据,为全市山区水土流失监测预报工作提供经验及方法,为制定水土流失防治方针政策及水土流失生态环境建设提供依据.     

Effect of fretting amplitudes on fretting wear behavior of steel wires in coal mines

Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation.     

Accelerated electrospark deposition and the wear behavior of coatings

Electrospark deposition (ESD) is a coating process that is featured by low heat input to the substrate. Low coating efficiency and other limitations influence its wider application. The present paper introduces newly designed ESD equipment, by which a higher coating rate can be reached. The relationship among coating thickness, surface roughness, and process parameters such as pulse energy, pulse frequency, and deposition time are presented. Electrospark deposition coating by the new equipment on AISI 1045 steel (with WC-8% Co as electrode) increases the wear resistance by 5 to 8 times. The micromechanism is investigated by scanning electron microscopy observation.     

Friction and the development of hard alloy surface microstructures during wear

Investigations of wear in sliding friction of WC-Hadfield steel hard alloy against cast tool steel have been carried out in a broad range of velocities and pressure values. Structural and phase composition variations have been revealed. Friction-affected zone was found to be 450 μm in depth. Structural γ → α, γ → transformation regions are located within 100 μm of the surface. These transformations contributed to the total solid solution deformation hardening.     

纳米Fe_2O_3作为润滑油添加剂的摩擦磨损性能

采用烧结方法制备得到纳米α-Fe_2O_3,利用X射线衍射仪(XRD)和透射电镜(TEM)对样品进行了表征,研究了纳米α-Fe_2O_3作为液体石蜡添加剂的摩擦磨损性能。结果表明,添加纳米添加剂后,润滑油摩擦系数改变不明显,但磨损率显著降低。磨损率与纳米α-Fe_2O_3添加剂的表面积和添加量密切相关,当纳米材料的表面积为47m~2/g时磨损率最低,磨损率值降低为3.78×10~(-15) m~2/g;添加量为1.0wt%,润滑油磨损率最低。     

水与可持续发展

论述了水在可持续发展中的地位。当今存在的4大水问题，评估了未来的水形势，提出了解决水问题的途径。     

Molecular dynamics studies of atomic-scale tribological characteristics for different sliding systems

A slider-slab sliding model for hard-to-soft and soft-to-soft sliding systems with abrasive and non-abrasive wear conditions is used to investigate atomic-scale friction. The molecular dynamics simulation uses the Morse potential to calculate interatomic forces between atoms. Separation distance between the slider and the slab is changed to simulate repulsive and attractive interactive force fields exerted on interface between two sliding components. Effects of the interaction potential parameters on the sliding friction are investigated. The relationship of frictional force, normal force and temperature rise of the slider and the slab during sliding are established. Comparison of the hard-to-soft and the soft-to-soft sliding system are carried out and shows different tribological phenomena.     

Comments on the sliding wear of metals

The author reviews selected experimental results which have contributed to improved understanding of sliding wear processes. The emphasis is on the chemical and structural changes which occur at and near the surface of metallic materials during sliding in different environments. The importance of plastic deformation, fracture, transfer, mechanical mixing, phase transformations and oxidation is discussed. Examples of transitions are described, and interesting correlations noted. In selecting the content of this paper, the author includes controversial results and conclusions and raises questions about the development of wear equations, interpretations of the wear coefficient, the importance of adhesion, the roles of hardness, the causes of transitions and the location of debris-producing cracks.     

The Effect of Coolant Concentration on the Machinability of Nickel-Base, Nimonic C-263, Alloy

This paper investigates the effect of coolant concentration on tool performance when machining nickel-base, C-263, alloy with triple coated (TiN/TiCN/TiN) carbide insert at various (3–9%) coolant concentrations and under different cutting speed conditions. Tool life, tool-failure modes, wear rates, component forces and surface finish generated during machining were recorded, analyzed and used to formulate mechanisms responsible for tool wear at the cutting conditions investigated. Analysis of the recorded data shows that tool performance during machining is dependent on coolant concentration. 6% coolant concentration gave the best overall performance as effective combination of cooling and lubrication functions were achieved during machining. Increasing coolant concentration to 9% reduced tool performance due to a reduction of the tool-chip contact length area and the consequent increase in compressive stresses at the tool-chip and tool-workpiece interfaces. This action often leads to pronounced chipping of the tool cutting edge during machining. Friction coefficient between the workpiece material and substrate increases once the coating layer(s) is broken as a result of the direct contact between the tool substrate and the work material. This action increases mechanical wear of the tool, which in turn leads to a significant increase in the cutting force with negligible effect on the feed forces during machining.