某类机械设备的磨损与抗磨损研究

煤矿机械利用率极高,且大部分设备都处于大负荷高强度的长期运作状态,很容易造成机械磨损等问题,为了满足当代煤矿市场对煤矿开采量以及机械生产效率的要求,需要针对煤矿机械设备磨损问题进行深入探究。本文从煤矿机械设备工作特点以及其磨损特征切入主题,从各影响因素分析机械磨损因素,以提出具有针对性的抗磨损措施,以保证煤矿机械设备生产工作的质量与效益。     

爆炸硬化处理对高锰钢冲击磨损性能影响的研究

对Mn13Cr2高锰钢进行了爆炸硬化处理。并分别以玻璃砂、鹅卵石为磨料，在MLD．10动载磨料磨损试验机上对比研究了爆炸前、后Mn13Cr2高锰钢的冲击磨损性能。实验结果表明：在低硬度磨料（玻璃砂）冲击磨损时，爆炸硬化使高锰钢的冲击耐磨性提高20％-40％。在高硬度磨料（鹅卵石）冲击磨损时，在冲击功小于1．7J的条件下，爆炸硬化使高锰钢的冲击耐磨性提高30—50％。在冲击功大予1．7J的条件下，爆炸硬化则使高锰钢的冲击耐磨性降低。爆炸硬化使高锰钢表层硬化和冲击韧性降低是冲击耐磨性发生变化的主要原因。在冲击磨损条件下，爆炸硬化前、后高锰钢磨损面均出现磨料嵌入物及犁沟、凿削坑和剥落坑等形貌特征。爆炸硬化高锰钢适用予低硬度磨料的冲击磨损及高硬度磨料的低冲击功冲击磨损的工况条件。     

沙尘环境对金属抗磨损特性的影响

通过向摩擦副所在隔离空间内鼓沙的方式实现对自然沙尘环境的模拟。在沙尘环境和干摩擦情况下,对比研究了随着载荷的增加,沙尘环境的存在对C52100铜、2124铝、AISI-1045钢、Z25铸铁、AISI-52100钢5种不同硬度的典型金属抗磨损行为的影响。结果表明,在沙尘条件下,5种金属的磨损率随载荷的变化呈现一定的变化规律,C52100铜和52100钢的磨损率均随载荷的增加而减小,2124铝和Z25铸铁的磨损率随载荷的增加而增大,而1045钢的磨损率则先增大后减小,但磨损率随载荷变化非常小。沙尘的存在使52100钢、1045钢和Z25铸铁的磨损率比干摩擦条件下有大幅度的减小,但是却加剧了2124铝在较高载荷下的磨损,这说明对不同的材料而言,沙尘所起的作用是不同的,它可能会加剧材料的磨损,但也有可能提高材料的抗磨损性能。     

石墨含量对石墨固体润滑涂层摩擦学性能的影响

利用简便的刷涂法在钢基体表面制备了石墨固体润滑涂层。利用MM-200型摩擦磨损试验机对不同石墨含量的固体润滑涂层进行了详细的摩擦学性能对比试验。结果发现．石墨固体润滑涂层的摩擦学性能与石墨含量之间呈“马鞍形”变化规律，当石墨的质量分数为28％时，固体润滑涂层的减摩、耐磨性能最佳。     

金属与金属接触型石墨密封垫片高温力学性能的试验研究

研究了金属与金属接触型石墨密封垫片在高温下的力学性能,包括压缩性能、回弹性能和蠕变松弛性能。根据试验结果获得了表征石墨垫片力学性能的拟合曲线和曲线方程,同时得到了石墨垫片在各温度下发生金属与金属接触时对应的接触应力。试验结果表明,温度影响石墨密封垫片的力学性能和接触应力。     

研磨液对陶瓷球耐磨性影响的实验研究

本文利用往复式和微幅式摩擦磨损实验机,在陶瓷球和轴承钢构成的运动副间加入不同的研磨液,对陶瓷球在不同研磨液时的摩擦磨损性能进行了实验研究,实验结果为陶瓷球研磨加工过程中不同阶段研磨液的选择提供了数据。     

内燃机润滑油添加剂抗磨损能力及其对发动机性能影响的试验研究

本文通过对几种选型的发动机润滑油添加剂的专用摩擦磨损试验机试验和发动机呆性能对比试验,证实了此类机油添加剂的减磨作用效果。分析了两种志用摩擦磨损试验机的试验结果与发动机性能试验结果的对应关系,从而提出了进一步试验研究的方向。     

SLM激光快速成型金属零件的组织及力学性能分析

为了对SLM快速成型不锈钢零件的组织及力学性能进行分析与研究,用SLM制备了拉伸试样进行拉伸试验,对其断口进行电镜扫描,分析其断裂特点;利用SLM设备制备了金属立体,进行显微硬度的测试、金相组织分析。实验结果表明:SLM快速成型金属件具有良好的拉伸性能、拉伸试样为韧性断裂;零件内部具有良好的致密性、晶粒细小,显微硬度高于一般奥氏体不锈钢;内部组织结构均匀,具有定向凝固特征;成型件物相主要以奥氏体存在。SLM成型金属件具有良好的组织特性及力学性能,能够满足实际使用的要求。     

Study of the formation of gouging pits in Mn7Cr2 steel under impact abrasive wear conditions

A study of the formation of gouging pits in Mn₇Cr₂ steel under impact abrasive wear conditions was conducted using theories of elastic impact and contact, analysis of photo‐elasticity, and scanning electron microscopy (SEM). The results show that the maximum shear stress occurs at z = 0. 48a, and this initiates a crack; the crack propagates at an angle of 45° from the horizontal; and the gouging pit is conical. The SEM observations are in agreement with the theoretical calculations.     

The use of impact plates in conveyor transfers

In the design of conveyor transfer stations for handling hard-rock mining products wear is one of the major factors that must be addressed. In a general discussion on the design of transfer stations for functionality, ease of maintenance and maximum life, the use and performance of impact plates are discussed. The necessity of keeping a small angle of impact between the ore stream and the plate is highlighted. Limited results from trials on the performance and wear resistance of hard-faced curved impact plates at a copper mine are presented. The mine is handling ore at rates in excess of 40 000 tonnes per day and had suffered from excessive transfer station wear and poor conveyor performance due to problems within the transfers. These problems had been exacerbated with the ore ranging over a wide range of moisture content to saturation and possible clay content to 15%.     

Effects of water-mixture film on impact contact in abrasive waterjet machining

The effects of a water-mixture film adhering to solid materials on the impact contact are examined by employing exact solutions for an inhomogeneous contact problem and the Hertz impact theory. The elastic modulus of the water on a surface is assumed to be zero and the modulus of the water-mixture between a water surface and a target material varies from zero to the modulus of the target material. Non-elastic deformation is considered based on an energy balance. A new expression of closed form for impact force is obtained. The film effect on the impact force is very significant for low impact energy and becomes stable and less influential once impact energy increases to a certain value. Experimental results for quasi-static force are in agreement with the theoretical analysis in which two unknown parameters are ascertained by experiments. The minimum effective velocity of garnet abrasives achieved in this work for waterjet machining is consistent with previous results.     

SiC和石墨颗粒混杂增强铜基复合材料的摩擦磨损性能

采用粉末冶金方法制备了SiC和石墨混杂增强铜基复合材料,研究了该复合材料在不同载荷条件下的摩擦磨损性能,并通过观察磨损表面形貌,研究其磨损机理。结果表明:在摩擦过程中,SiC颗粒作为载荷的主要承载单元,起到了较好的硬质承载支点的作用,石墨颗粒则发挥了较好的自润滑减摩效果,二者协同作用明显提高了铜基复合材料的耐磨性;该复合材料的磨损机理主要以磨粒磨损为主。     

Investigations on the influence of graphite filler on dry sliding wear and abrasive wear behaviour of carbon fabric reinforced epoxy composites

In this experimental study, the dry sliding wear and two-body abrasive wear behaviour of graphite filled carbon fabric reinforced epoxy composites were investigated. Carbon fabric reinforced epoxy composite was used as a reference material. Sliding wear experiments were conducted using a pin-on-disc wear tester under dry contact condition. Mass loss was determined as a function of sliding velocity for loads of 25, 50, 75, and 100 N at a constant sliding distance of 6000 m. Two-body abrasive wear experiments were performed under multi-pass condition using silicon carbide (SiC) of 150 and 320 grit abrasive papers. The effects of abrading distance and different loads have been studied. Abrasive wear volume and specific wear rate as a function of applied normal load and abrading distance were also determined.The results show that in dry sliding wear situations, for increased load and sliding velocity, higher wear loss was recorded. The excellent wear characteristics were obtained with carbon-epoxy containing graphite as filler. Especially, 10 wt.% of graphite in carbon-epoxy gave a low wear rate. A graphite surface film formed on the counterface was confirmed to be effective in improving the wear characteristics of graphite filled carbon-epoxy composites. In case of two-body abrasive wear, the wear volume increases with increasing load/abrading distance. Experimental results showed the type of counterface (hardened steel disc and SiC paper) material greatly influences the wear behaviour of the composites. Wear mechanisms of the composites were investigated using scanning electron microscopy. Wear of carbon-epoxy composite was found to be mainly due to a microcracking and fiber fracture mechanisms. It was found that the microcracking mechanism had been caused by progressive surface damage. Further, it was also noticed that carbon-epoxy composite wear is reduced to a greater extent by addition of the graphite filler, in which wear was dominated by microplowing/microcutting mechanisms instead of microcracking.     

The effect of brush spring pressure on the wear behaviour of copper–graphite brushes with electrical current

Electrical brushes are used to conduct current between stationary part and moving part of a motor or a generator. To ensure proper current transfer and continuous contact, brushes must be loaded against the sliding contact surface with a sufficient force. High loads increase frictional losses and wear of the brushes and/or sliding surface. While relatively low contact pressure causes arcing and higher voltage drop.In this study, a novel pin-on-slip ring-type friction and wear test machine was designed and manufactured for the purpose of brush testing. Copper–graphite-based electrical brush containing 90 wt% copper and 10 wt% graphite was manufactured by powder metallurgy and the tribological behaviour and voltage drop were investigated at different brush spring pressures at 10–200 kPa with current.It was found that the specific wear curve showed three distinct wear rate regimes, such as low, mild, and severe. Severe wear was observed below 30 kPa and above 120 kPa brush spring pressures (BSP) (3 and 12 N loads, respectively). Arc erosion was the main wear mechanism below 30 kPa brush spring pressure while abrasion was dominant above 120 kPa BSP. Low and mild regimes were observed between 30–50 and 50–120 kPa BSP, respectively. SEM observations showed that a continuous surface layer was formed at the sliding surfaces of the wear samples in low and mild wear regimes. The wear debris was examined by SEM and X-ray diffractometer.     

The effect of a vacancy on the STM image of graphite

Theoretical studies have been done on graphite with a vacancy using the extended Huckel tight-binding (EHTB) method. The results of the singly- and doubly-layered samples show that there is an unexpected distance dependence of the charge density directly over the vacancy. Furthermore, the vacancy acts as a perturbation to distinguish two sublattices which exist in pristine graphite and it creates a charge enhancement in the atoms directly surrounding it.     

换阀芯平衡阀的流量特性实验研究

通过对几组换阀芯平衡阀的实验,得到了换阀芯平衡阀的流量特性数据,绘制了换阀芯平衡阀的流量特性曲线,并与原阀芯平衡阀进行了性能比较,确定了换阀芯平衡阀产品的工程应用价值。     

Investigation on MoS2 and graphite coatings and their effects on the tribological properties of the radial spherical plain bearings

With constant enlargement of the application areas of the spherical plain bearings, higher quality lubrication of the bearings is required. To solve the lubricating problems of spherical plain bearings under high temperature, high vacuum, high speed, heavy loads and strong oxidation conditions, it is urgent for us to develop more excellent self-lubricating technologies. In this paper, the bonded solid lubricant coatings, which use inorganic phosphate as the binder, the mixture of MoS2 and graphite with two different weight proportions as the solid lubricant, are prepared by spraying under three different spray gun pressures. The bonding strength tests on the coatings show that the best spraying pressure is 0.2 MPa and the better mixing proportion of MoS2 to Graphite is 3:1. Then for the radial spherical plain bearings with steel/steel friction pair, after the coatings are made on the inner ring outer surfaces, the friction coefficient, the wear loss and the friction temperature of the bearings under four oscillating frequencies are investigated by a self-made tribo-tester. The test results, SEM of the worn morphologies and EDS of worn areas show that tribological properties of the bearing are obviously improved by the bonded solid lubricant coatings. When sprayed under the spray gun pressure of 0.2 MPa, the bearings have better anti-friction and anti-wear properties than those sprayed under 0.1 MPa and 0.3 MPa. Further as proved from the XPS analysis, between the coating with 3:1 mixing ratio of MoS2 to Graphite and the coating with 1:1 ratio, the former has less oxidation occurred on the surface and therefore has better tribological characteristics than the latter. This paper provides a reference to developing a new product of the radial spherical plain bearings with high bonding strength, oxidation resistance and abrasion resistance.