Effect of solid lubricant and fibrous reinforcement on the abrasive wear of polyamides

Short glass fibre‐reinforced polyamide 6 and polyamide 11 (PA 6 and PA 11) with and without a solid lubricant of polytetrafluoroethylene and metal powders (e.g., bronze) and copper as fillers were formulated and characterised for their compositional and mechanical properties. A tribological evaluation of these composites' abrasive wear was carried out by abrading a polymer pin against 80 grade (175 um) silicon carbide (SiC) paper under single‐pass conditions at various loads. It was observed that the fibre reinforcement reduced the abrasive wear resistance of virgin polymers. A combination of fibre and particulate fillers was further detrimental in this respect. Efforts were made to correlate the wear performance with the ductility factor, fracture toughness, and fracture energy in the case of PA 6 and its composites.     

On the abrasive wear behaviour of mineral filled polypropylene

The effects of mineral fillers on the wear resistance of polypropylene (PP) have been investigated. A general purpose homopolymer grade was used as the matrix. The mineral fillers investigated were talc, CaCO₃, BaSO₄ and fly ash, representing a range of morphology, size and hardness. The wear behaviour was assessed by pin-on-paper abrasion tests. The wear surfaces were examined using scanning electron microscopy (SEM). The addition of mineral fillers to the polypropylene matrix decreases the wear resistance under severe abrasive conditions. Under mild abrasive conditions the shape and size of the reinforcing filler influence the wear performance. The tensile strength behaviour of each composite, together with the physical properties of the fillers and a microscopic investigation into the modes of material deformation and removal are used to interpret this observed wear behaviour.     

Influence of solid lubricants and fibre reinforcement on wear behaviour of polyethersulphone

Polyethersulphone (PES), is an amorphous, brittle and high temperature engineering thermoplastic. Two composites of PES containing short glass fibres (GF) and solid lubricants viz. PTFE and MoS₂; and two composites containing short carbon fibre (CF) [30% and 40%] were selected for the present studies. Compositional analysis of selected materials was done with various techniques such as gravimetry, solvent extraction and thermal analysis viz. thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). These materials were studied for adhesive and abrasive wear performance by sliding against a mild steel disc and silicon carbide abrasive paper respectively, under different loads. It was observed that GF reinforcement along with incorporation of solid lubricants (PTFE and MoS₂) enhanced the wear performance of PES by an order of two. In the case of solid lubricants, PTFE proved to be more beneficial than MoS₂. CF reinforcement, however, proved to be the most effective in enhancing wear performance of PES. PES reinforced with 40% CF exhibited a specific wear rate in the order of 10⁻¹⁶m³/Nm which is considered to be very good for the thermoplastic composite. In the case of abrasive wear behaviour, however, incorporation of fibres or solid lubricants deteriorated the performance of the neat matrix. SEM was employed to investigate the wear mechanisms.     

Observations on the effectiveness of some surface treatments of mineral particles and inorganic compounds from Armenia as the fillers in polyphenylene sulfide for tribological performance

This is a general study in which a number of minerals and inorganic compounds from Armenia were investigated for their effectiveness as the fillers in polyphenylene sulfide (PPS) for tribological performance. The minerals studied were tuff, bentonite, and travertine, and inorganic compounds MoO₃ and MoO₂. The filled polymer specimens were prepared by compression molding and tested for tribological behavior in the pin-on-disk sliding configuration. The particulate fillers included many variations in terms of the size (micro and nano) and surface treatment. Friction and wear test results revealed that MoO₂ and nano size bentonite particles were effective in improving the wear resistance. The lowest steady state wear rate in this study was observed for PPS+7% MoO₂ (50 nm)+5% PTFE composite, and MoO₂-filled composites had generally lower coefficients of friction than that of the unfilled PPS. From the wear plots, filler abrasiveness, and transfer film studies, it was concluded that the abrasion by filler was mostly responsible for the detrimental wear behavior. The wear behavior has been discussed in terms of the abrasion by filler and transfer film uniformity, texture, thickness, and coverage. The effects of particulate size and surface treatment are also included in the discussion. In view of the results reported for these fillers in formaldehyde and dioxolane copolymer (CFD) and the observations in this study, it is felt that the fillers from Armenia with the exception of tuff and MoO₃ have considerable appeal for further investigation using other innovative surface treatments for fillers.     

配副材料对碳纤维增强环氧树脂复合材料摩擦学性能的影响

采用铺层/热压烧结的方法制备交叉铺层的碳纤维增强环氧树脂复合材料,探究配副材料及载荷对铺层材料摩擦学性能的影响,并探讨复合材料的磨损机制。结果表明:随着载荷的增加,复合材料的摩擦因数逐渐降低,磨损率则逐渐增加;在研究的载荷下,复合材料与轴承钢配副时摩擦因数较低,而与Si₃N₄和Al₂O₃陶瓷球配副时润滑性能较差;在低载荷下复合材料与轴承钢配副时磨损率较高,高载荷下则相反。磨损表面形貌分析显示:当施加的载荷较低时,磨损表面形貌主要为犁沟及少量裂纹,磨损机制主要为磨粒磨损;当载荷较高时,高的接触应力使磨损表面产生了大量裂纹并伴随树脂基体脱落,磨损机制由磨粒磨损转变为疲劳磨损。     

The friction properties of an ultrathin confined water film

A factorial design approach technique was adopted to understand the high stress abrasive behaviour of a diamond reinforced composite coating for various compositions at different loads and abrasive sizes. A linear regression equation was developed and used for understanding the influence of the diamond concentration, applied load, and abrasive sizes on the wear response. A negative value of the coefficient associated with diamond concentration, together with its interactions with the applied load; suggest that the wear rate decreases with increasing diamond concentration. By contrast, a positive coefficient suggests an increase in wear rate due to an increase in related factors such as the applied load and abrasive size. The coefficients associated with the interactions of the parameters are insignificant by comparison with the individual parameters, thereby demonstrating that the interaction effect of these parameters towards the wear rate is insignificant. The wear rate may be extracted in terms of the diamond concentration, the applied load and the abrasive grit size using the above linear regression equation.     

WC颗粒增强铁基表面复合材料的三体磨料磨损性能研究

设计、制备了一台三体磨料磨损实验机，对该实验机进行了重现性实验。以高铬铸铁为标样，利用该磨损实验机分别考察了WC颗粒体积分数、载荷与表面复合材料相对耐磨性能之间的关系。实验结果表明：本实验机的测试性能是可靠的；复合材料的三体磨料磨损性能与高铬铸铁标样相比有较明显的提高，在同一载荷下．复合材料的相对耐磨性能随着WC颗粒体积分数的增大呈先升高后降低的变化规律，WC颗粒体积分数为27％的复合材料相对耐磨性最高，达到高铬铸铁的5．12倍；而对于同一种复合材料，随着载荷的增大，其相对耐磨性呈增加趋势，其中WC颗粒体积分数为27％的复合材料增加最为明显；复合材料的三体磨料磨损机理为WC对周围组织的屏蔽作用，失效方式为WC颗粒因疲劳而片状剥落。     

Dimensional analysis for abrasive wear behaviour of various polyamides

Abrasive wear behaviour of a series of polyamides (PAs) with different methylene to amide ratio (CH₂/CONH) was analysed using Buckinghams dimensional analysis method and efforts for quantifying the contribution of the material properties towards the abrasive wear performance were also made. In order to calculate the wear coefficient (K), the data based on the experimental wear volume, operating parameters and the material properties were fitted into the non-linear wear equation. The non-linear wear equation was derived based on pi theorem using the dimensional analysis technique. The wear coefficient K decreased as load and abrasive grit size were increased. The theoretical and experimental wear volume correlated well in most of the cases. Among the selected material properties, the fracture stress (_*) and the critical crack length (C_*) were found to be the most important parameters, which controlled the abrasive wear behaviour of PAs.     

Microstructure and abrasive wear resistance of cast Ni-Cr-C alloys

The abrasive wear behaviour of directionally solidified Ni-Cr-C alloys was investigated using a pin-type test. M₇C₃ carbide volume fractions (CVF) were varied from 0 to 40%. Two sets of alloys with different carbide and dendrite spacings were abraded with bonded SiC and corundum particles, varying the grit size and applied load. M₇C₃ carbides greatly improved the abrasive wear resistance against fine-grained SiC particles within the whole range of compositions. By refining the primary carbide structure in hypereutectic alloys, the wear resistance against coarse-grained SiC particles was also improved with increasing CVF although SiC is known to be much harder than M₇C₃. Coarse SiC abrasive particles had a detrimental effect on the wear resistance of all hypoeutectic alloys and, even more, of hypereutectic alloys if the primary carbides were coarse. In testing with corundum, the wear resistance always improved with increasing carbide volume fraction.Wear damage was arranged in three classes. First, SiC and corundum abrasives were partially broken from the substrate at the entrance edge of the specimen. The edges of SiC grains stayed sharp during the wear process whereas the edges of corundum particles were rounded or the corundum was crushed by M₇C₃ carbides. Secondly, damage in the wear surface occurred by fracturing of the edges of carbides facing the wear surface. In addition, SiC abrasives were able to groove carbides. Thirdly, coarse SiC grains transmitted shear stresses causing severe subsurface damage leading to microstructure disintegration and spalling of primary carbides. SiC transmitted larger shear stresses than corundum because the latter was separated by a thin layer of wear debris from the unworn material.The microstructural parameters influencing wear were CVF, size, morphology and distribution of carbides. Optimum wear resistance depended on the abrasive mineral. Alloys with high CVF and coarse primary carbides were best suited for wear with corundum whereas fine primary carbides were required to resist wear by SiC.     

On the feasibility of using cryo‐treatment as a tool to enhance the abrasive wear behaviour of solid‐lubricated polymeric composites

Cryo‐treatment, a bulk modification technique, is fast emerging as a way with which to improve the wear resistance of metals. This technique has also shown the ability to enhance significantly the abrasive wear performance of some polymers and their short glass‐fibre reinforced composites. In this work, short carbon‐fibre reinforced composites of some heat resistant polymers, such as polyetherimide, polyethersulphone, polyamide 6,6, polyetheretherketone, and polytetrafluoroethylene, were selected to explore the potential of cryo‐treatment. The selected materials were cryogenically treated by cooling them to the temperature of liquid nitrogen. The abrasive wear tests were carried out at ambient temperature in single pass conditions at various loads, on a pin‐on‐disc machine, using silicon carbide paper as a counterface. The investigations revealed that this technique has definite potential to increase the wear performance of carbon‐fibre reinforced composites. An increase in hardness due to cryo‐treatment was thought to be responsible for an observed improvement in wear performance. However, the extent of improvement in the wear performance was not matched by an increase in the hardness value. Scanning electron microscopy proved useful in examining the morphological changes in the composites due to cryo‐treatment.     

Cu-3镍铜合金砂带磨削试验研究

分析了Cu-3镍铜合金砂带磨削加工过程中,砂带粒度和磨削用量的不同对磨削加工效率、工件表面质量和砂带磨损的影响。采用氧化铝磨料砂带在不同的砂带线速度或磨削压力下对镍铜合金进行了工艺试验,对材料去除量、工件表面粗糙度和砂带磨损量进行了测量。研究表明:增加砂带线速度和磨削压力可在一定程度上提高材料去除率和磨削比;随着磨削压力的增大,工件表面粗糙度呈增大趋势;随着砂带粒度的增大,工件表面粗糙度呈减小趋势;砂带线速度为25m/s,磨削压力为43N,砂带粒度为P240时,镍铜合金综合磨削效果最好。     

Ductility and the abrasive wear resistance of hot work die steels

Two-body abrasive resistance has been determined as a function of tempering temperature for a conventional hot work die steel and two experimental hot work die steels. After tempering in the secondary hardening range both experimental steels exhibit abrasive wear resistance comparable with or superior to that of the conventional die steel. In addition, the abrasive wear behavior of the three steels has been assessed using an approach suggested by one of the authors which emphasizes the role of ductility in determining abrasive wear resistance. As suggested by that approach, the product of the wear ratio and the bulk hardness tends to decrease with increasing tensile strain to fracture.     

Abrasive wear of a single CBN grain in ultrasonic-assisted high-speed grinding

Research into the single grain cutting mechanism is important for understanding complex grinding mechanisms. Based on the characteristics of ultrasonic vibration, the motion equation of the grain is established, and the generated trajectory is theoretically analyzed. By adopting the method of combining high-speed grinding technology with ultrasonic vibration, abrasive wear forms of single cubic boron nitride (CBN) grains under common and ultrasonic conditions are studied. Further studies are conducted on the influence of the grain itself and the main grinding parameters on abrasive wear. Research shows that the main forms of abrasive wear during ultrasonic-assisted grinding are shearing wear and removing wear. However, common grinding leads to micro-crushing wear and a small amount of abrasion wear; the different forms of wear correspond to different grinding force signals. The greater the initial grain protrusion height, the greater is the abrasion of the protrusion; for the same grain protrusion height, the abrasive wear due to ultrasonic-assisted grinding is larger than that due to common grinding. As the grinding depth increases, the abrasive wear of both processing modes increases; however, in the case of ultrasonic machining, the abrasive wear increases slowly and is larger than that under common grinding. This study provides a certain decision basis for real-time monitoring of the ultrasonic-assisted high-speed grinding process. Additionally, it provides guidance and reference for the manufacture and selection of the grinding wheel and for the selection of reasonable processing parameters.     

Abrasive erosive wear of powder steels and cermets

Composite materials produced by powder metallurgy provide solutions to many engineering applications that require materials with high abrasive wear resistance. The actual wear behaviour of a material is associated with many external factors (abrasive particle size, velocity and angularity) and intrinsic material properties of wear (hardness, toughness, Young modulus, etc.). Hardness and toughness properties of wear resistant materials are highly dependent on the content of the reinforcing phase, its size and on the mechanical properties of the constituent phase. This study is focused on the analysis of the (AEW) abrasive erosive wear (solid particle erosion) using different wear devices and abrasives. Powder materials (steels, cermets and hardmetals) were studied. Wear resistance of materials and wear mechanisms were studied and compared with those of commercial steels. Based on the results of wear studies, surface degradation mechanisms are proposed. The following parameters characterizing the materials were found necessary in materials creation and selection: hardness (preferably in scale comparable with impact), type of structure (preferably hardmetal type) and wear parameters characterizing material removal at plastic deformation.     

Computational investigation of testing parameter effects on abrasive wear behaviour of AL2O3 particle-reinforced MMCS using statistical analysis

The wear rate model of 7.3?vol.% Al₂O₃ particle-reinforced aluminium alloy composites with 16 and 66???m particle sizes fabricated by molten metal mixing method was developed in terms of applied load, particle size of reinforcement, abrasive grain size and sliding distance based on the Taguchi method. The two-body abrasive wear behaviour of the specimens was investigated using a pin-on-disc abrasion test apparatus where the sample slid against different SiC abrasives under the loads of 2 and 5?N at the room conditions. The orthogonal array, signal-to-noise ratio and analysis of variance were employed to find out the optimal testing parameters. The test results showed that particle size of reinforcement was found to be the most effective factor among the other control parameters on abrasive wear, followed by abrasive grain size. Moreover, the optimal combination of the testing parameters was determined and predicted. The predicted wear rate results were compared with experimental results and found to be quite reliable.     

阳极/阴极面积比对Zr-4合金腐蚀磨损的影响

采用往复磨损实验机完成了Zr-4合金/Al2O3摩擦副在Na2SO4溶液中的腐蚀磨损实验。试验在改变负荷及试样的阳极/阴极面积比时,对腐蚀磨损的影响作了分析。用三坐标表面粗糙度仪测量了磨损体积,利用脉冲电位评价磨损产生的新生面与磨损表面的关系。结果表明:随着负荷的增加,自然电位下降而磨损量成正比例增加。电化学腐蚀作用随试样阳极/阴极的面积比的减小而增大。磨损面损伤的主要表现为磨粒磨损和粘着磨损的共同作用。     

Preliminary studies of the influence of cryo‐treatment on the mechanical and tribological properties of ptfe and composites

Cryogenic treatment of polytetrafluoroethylene (PTFE) has proved beneficial in improving the abrasive wear resistance of several polymers, and it was thus assessed in an adhesive wear mode, as well. Preliminary investigations on the effect of cryogenic treatment on the tribological properties, in adhesive wear mode, and mechanical properties of neat PTFE and it composites filled with bronze or short glass fibres (GF) were carried out. It was found that, although the improvement in the wear and friction performance of neat PTFE and a GF + PTFE composite was significant, no such positive effect was observed for the bronze + PTFE composite. On the contrary, this composite showed a deterioration in performance. The reason behind the improvement in the tribological behaviour of neat PTFE and the GF + PTFE composite could not be clearly understood. However, it was confirmed that, if the treatment adversely affected the mechanical properties, then the tribological performance also deteriorated. An examination of the worn surface of the material and the counterface disc using a scanning electron microscope revealed changes in the microstructure due to the treatment. It was also confirmed from these SEM studies that the compatibility of bronze and PTFE was very poor, which led to poor performance of the composite both in the untreated and the cryo‐treated form. Further detailed investigation and analysis of various materials and composites, however, are necessary to establish the utility of this technique.     

Influence of PTFE content in PEEK-PTFE blends on mechanical properties and tribo-performance in various wear modes

Few papers are available on the optimum composition of PEEK-PTFE blends for the best possible combination of mechanical and tribological properties in the adhesive wear mode. Nothing is reported in this context on low amplitude oscillating/fretting wear mode. Moreover, the influence of increasing amounts of PTFE in the blend on abrasive wear behaviour along with a correlation with strength properties is not reported. Hence, in this work, five injection-moulded blends of PEEK with PTFE (in the range of 0-30 wt.%) were evaluated on a pin-on-disc configuration on an SRV Optimol Tester for their tribo-behaviour in the low amplitude oscillating wear mode. The data in the abrasive wear mode were generated by abrading a pin loaded against an abrasive paper fitted on the rotating disc. Data on neat PTFE were also included for comparison. It was observed that inclusion of PTFE affected the adhesive wear and low amplitude oscillating wear (LAOW) in a beneficial way. With an increase in PTFE contents, coefficient of friction in both the wear modes (adhesive and low amplitude oscillating) decreased but the trends in wear performance differed. In the adhesive wear mode, the specific wear rate showed minima for 7.5% PTFE inclusion followed by a slow increase for further PTFE addition. In the case of LAOW mode, on the other hand, the wear rate continuously decreased for the selected compositions. The 30% PTFE blend showed excellent combination of μ, wear rate and limiting pressure-velocity (PV) values. Unfilled PEEK proved to be fairly good wear-resistant material but exhibited high μ, a stick-slip tendency and a low PV limit value. Abrasive wear performance of the blends on the other hand, deteriorated with increasing amount of PTFE. Fairly good correlation was observed between the wear rate and product of H and S (H-hardness and S-ultimate tensile strength) rather than Ratner-Lancaster plot (product of S and e, where e is elongation to break).Thus, with increase in PTFE contents, though adhesive and LAOW performance increased substantially, it was at the cost of deterioration in all mechanical properties (except impact strength) and abrasive wear performance.     

热轧高锰钢Mn13的冲滚磨料磨损性能

在M2000摩擦磨损试验机上,研究以煤矸石为磨料时热轧高锰钢Mn13冲滚耦合的磨料磨损性能,利用XRD和SEM分析其组织转变及磨损机制。实验结果表明,在较高冲滚载荷下,热轧Mn13钢表现出更好的抗冲滚磨料磨损性能;冲滚磨料磨损表面存在一定厚度的硬化层,且随冲滚载荷的增加,磨损面硬度增加,硬化层厚度增大,形变孪晶和马氏体相变是其加工硬化和耐磨损性能改善的主要原因;低载荷冲击时,磨损机制主要表现为凿削磨损并伴随犁沟切削磨损,较高载荷冲击时,磨损机制凿削磨损和犁沟划伤过渡到疲劳剥落和凿削磨损。     

模拟矿井环境下的PEEK/SiO2/CF-MoS2复合材料摩擦行为研究*

为改善聚醚醚酮（PEEK）在矿井工况下的摩擦性能,选用纳米二氧化硅（SiO2）、二硫化钼（MoS2）和短切碳纤维（CF）为增强填料制备PEEK/SiO2/CF-MoS2复合材料,并探究PEEK/SiO2/CF-MoS2复合材料在不同工况条件下的滑动与滚动摩擦学性能;通过模拟滚轮罐耳在矿井环境下的运行方式,分析其磨损形貌和磨损机制。结果表明：PEEK/SiO2/CF-MoS2复合材料在不同载荷条件下均具有良好的减摩和耐磨特性;滑动摩擦在水介质工况下及滚动摩擦在干摩擦工况下,复合材料的摩擦因数和磨损率最低,其磨损机制均以磨粒磨损为主。与矿井常用的聚氨酯材料的对比,PEEK/SiO2/CF-MoS2复合材料的摩擦学性能更为优异。