The relationship between the abrasive wear resistance,hardness and microstructure of ferritic materials

The relationship between the abrasive wear resistance and bulk hardness of ferritic materials in the pearlitic and martensitic conditions has been investigated. For pearlitic materials the abrasive wear resistance and bulk hardness are dependent on the pearlite content and for martensitic materials the abrasive wear resistance and bulk hardness are dependent on the square root of the carbon content. Thus for each structure there is a linear relationship between abrasive wear resistance and bulk hardness, but it is suggested that the material microstructure has a greater influence on wear resistance than the bulk hardness.     

Abrasive wear resistance of some commercial abrasion resistant steels evaluated by laboratory test methods

The aim of the present study is to evaluate the abrasive wear resistance of some potential abrasion resistant steels exposed to different types of abrasive wear contact conditions typical of mining and transportation applications. The steels investigated, include a ferritic stainless steel, a medium alloyed ferritic carbon steel and a medium alloyed martensitic carbon steel.The abrasive wear resistance of the steels was evaluated using two different laboratory test methods, i.e. pin-on-disc testing and paddle wear testing that expose the materials to sliding abrasion and impact abrasion, respectively. All tests were performed under dry conditions in air at room temperature. In order to evaluate the tribological response of the different steels post-test characterization of the worn surfaces were performed using optical surface profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. Besides, characterization of the wear induced sub-surface microstructure was performed using optical microscopy.The results show that depending on the abrasive conditions a combination of high hardness and toughness (fracture strain) is of importance in order to obtain a high wear resistance. In the pin-on-disc test (i.e. in sliding abrasion) these properties seem to be controlled by the as-rolled microstructure of the steels although a thin triboinduced sub-surface layer (5–10 μm in thickness) may influence the results. In contrast, in the paddle wear test (i.e. in impact abrasion), resulting in higher forces acting perpendicular to the surface by impacting stones, these properties are definitely controlled by the properties of the active sub-surface layer which also contains small imbedded stone fragments.     

石墨种类对铜基粉末冶金摩擦材料性能的影响

采用柔性石墨、造粒石墨和鳞片石墨分别制备粉末冶金烧结摩擦材料，研究不同种类片状石墨对摩擦材料摩擦磨损性能的影响。结果表明：不同种类石墨制备的摩擦材料的密度和力学强度差异，将影响材料基体在制动过程中的组织形态，使摩擦界面呈现不同的磨损形式，其中柔性石墨摩擦材料的主要磨损机制为氧化磨损，造粒石墨摩擦材料的主要磨损机制为犁削磨损和磨粒磨损，鳞片石墨摩擦材料的主要磨损机制为犁削磨损和黏着磨损；造粒石墨制备的摩擦材料在不同速度下制动和重复单次制动时的摩擦因数波动值较小，摩擦因数稳定性好，且具有适中的磨耗量，综合摩擦磨损性能最佳。     

Abrasive wear resistance of starch consolidated and sintered high speed steel

The abrasive wear resistance of starch consolidated (SC) and super solidus liquid phase sintered (SLPS) M3/2 high speed steel (HSS) samples have been evaluated by a two-body micro-abrasion test (low stress abrasion), using 6 μm diamond abrasive particles, and a three-body abrasion test (high stress abrasion), using significantly larger abrasive particles of blast furnace slag (600 HV) and silicon carbide (2400 HV), respectively. In the tests a commercial powder metallurgical (PM) HSS was used as a reference material.The results show that the microstructure of the SC and SLPS HSS samples is strongly dependent on the sintering temperature used. With increasing temperature the microstructure ranges from a porous (5% porosity) relatively fine grained low temperature sintered microstructure to a fully dense relatively coarse grained high temperature sintered microstructure with eutectic carbides/carbide networks. However, despite the pronounced microstructural differences displayed by the as-sintered HSS microstructures these show a relatively high abrasive wear resistance, comparable with that of a HIPed HSS reference, both under low and high stress abrasion contact conditions. The characteristic features of the low and high temperature sintered microstructures, i.e. the pores and coarse eutectic carbides/carbide networks, only show a limited impact on the wear rate and the wear mode (dominant wear mechanism). The results obtained imply that near net shaped components manufactured by starch consolidation and super solidus liquid phase sintering might be of interest in tribological applications.     

Wear of aligned silicon nitride under dry sliding conditions

The wear behaviour of textured silicon nitride (Si₃N₄) ceramics with aligned microstructures was analyzed under abrasive wear conditions. Dry reciprocating self-mated ball-on-flat wear tests were performed to study the influence of different microstructural plane/orientation combinations on the Si₃N₄ tribological behaviour. Textured materials showed superior wear resistance than non-textured reference Si₃N₄ for the whole range of loads and contact pressures, 5–50 N and 1.7–3.6 GPa, respectively, with an increase of about 70% for the maximum applied load. Within textured materials, the plane perpendicular to the extruding direction exhibited a 50% higher wear resistance (4 × 10^?5 mm³ N^?1 m^?1) than the parallel plane where the elongated grains were aligned. The severe wear process involved debonding, fracture and debris formation mechanisms. The progress of this sequence depended on the particular microstructure of each plane/orientation combination. A relationship between abrasive wear resistance and selected microstructural parameters has been established.     

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.     

Microstructure and abrasive wear in silicon nitride ceramics

It is well known that abrasive wear resistance is not strictly a materials property, but also depends upon the specific conditions of the wear environment. Nonetheless, characteristics of the ceramic microstructure do influence its hardness and fracture toughness and must, therefore, play an active role in determining how a ceramic will respond to the specific stress states imposed upon it by the wear environment. In this study, the ways in which composition and microstructure influence the abrasive wear behavior of six commercially-produced silicon nitride based ceramics are examined. Results indicate that microstructural parameters, such as matrix grain size and orientation, porosity, and grain boundary microstructure, and thermal expansion mismatch stresses created as the result of second phase formation, influence the wear rate through their effect on wear sheet formation and subsurface fracture. It is also noted that the potential impact of these variables on the wear rate may not be reflected in conventional fracture toughness measurements.     

聚乙烯亚胺修饰碳纤维对环氧树脂复合材料性能的影响

为提高碳纤维与环氧树脂的界面结合性能,从而提高复合材料的摩擦学性能,用聚多巴胺和聚乙烯亚胺对碳纤维进行表面修饰,利用光谱分析仪和扫描电子显微镜分析修饰前后碳纤维表面的化学组成和微观结构,利用万能材料试验机和摩擦磨损试验机考察碳纤维增强环氧树脂复合材料的力学性能和摩擦学性能。结果表明：碳纤维经表面处理之后的粗糙程度和活性官能团增多,改善了纤维与树脂之间的界面结合,使得复合材料的弯曲强度和拉伸强度得到不同程度的提高;与未修饰碳纤维增强的环氧树脂复合材料相比,表面修饰碳纤维增强环氧树脂复合材料的耐磨性能得到了很大程度的提高,复合材料的磨损机制也由疲劳磨损转变为磨粒磨损。     

Investigation on Wear Resistance and Fatigue Damage of Laser Cladding Coating on Wheel and Rail Materials under the Oil Lubrication Condition

The aim of this study is to investigate the wear resistance and fatigue spalling damage of wheel and rail materials with and without laser cladding coating under oil lubrication using a rolling–sliding machine. It illustrates that the laser cladding Co-based alloy coating improves the wear resistance of wheel and rail rollers. Serious spalling is dominant for untreated wheel and rail rollers. The wheel or rail roller undergoing laser cladding treatment takes on slight abrasive wear and visible ploughing. Furthermore, there are no cracks on the contact surface and subsurface. The laser cladding Co-based alloy coating exhibits outstanding resistance to wear and fatigue spalling damage due to its microstructure in the coating under oil lubrication.     

A comparative investigation of the wear behavior of PTFE and PI under dry sliding and simulated sand-dust conditions

The wear behavior of polytetrafluoroethylene (PTFE) and polyimide (PI) has been comparatively evaluated under dry sliding and simulated sand-dust conditions. An improved block-on-ring wear tester equipped with an attachment for simulating the sand-dust environment was used to evaluate the abrasive wear behavior of materials. The sand collected from the Yellow River of China was used to simulate the sand-dust environment, also different loads and sand-dust sizes were chosen for tribological tests. The two chosen polymers showed different wear behavior under sand-dust conditions and the wear rates of PTFE were much lower under sand-dust conditions than under dry sliding conditions. This was attributed to the formation of the tribolayer on the worn surfaces during the abrasive wear process. The sand-dust enhanced the wear resistance of PTFE, but reduced that of PI because, in contrast to PTFE, there was no tribolayer formed on the PI worn surface. The wear rate of PTFE increased under sand-dust conditions while the wear rate of PI decreased with the increase of applied load. The higher hardness of PI and fragmentation of abrasive particles under high loads accounted for the decrease in wear rate as load increased.     

Effect of nanosilica additive particles on both friction and wear performance of mild steel/CuSn/SnBi multimaterial system

This paper presents an experimental study of the tribological behaviour of a multimaterial system using conventional powder metallurgy process with SiO₂ nanoparticles. Four configurations were studied with and without SiO₂. The tribological properties of the sintered materials were analysed by wear experiments at lubricated conditions on a ball disc wear test rig. The results are compared with those of conventional material for journal bearing. These show less variation of the friction coefficient and less wear rate for the materials with SiO₂ compared to the ones without SiO₂ and to those of the reference material. The dominant wear mechanism is adhesive wear, accompanied by mild abrasive wear.     

Microstructure and Tribological Properties of a HfB<Subscript>2</Subscript>-Containing Ni-Based Composite Coating Produced on a Pure Ti Substrate by Laser Cladding

A HfB₂-containing Ni-based composite coating was fabricated on Ti substrates by laser cladding, and its microstructure and tribological properties were evaluated during sliding against an AISI-52100 steel ball at different normal loads and sliding speeds. The morphologies of the worn surfaces were analyzed by scanning electron microscopy (SEM) and three-dimensional non-contact surface mapping. The results show that wear resistance of the pure Ti substrate and NiCrBSi coating greatly increased after laser cladding of the HfB₂-containing composite coating due to the formation of hard phases in the composite coating. The pure Ti substrate sliding against the AISI-52100 counterpart ball at room temperature displayed predominantly adhesive wear, abrasive wear, and severe plastic deformation, while the HfB₂-containing composite coating showed only mild abrasive wear and adhesive wear under the same conditions.     

Tribological Behavior of New Martensitic Stainless Steels Using Scratch and Dry Wear Test

This paper focuses on the tribological characterization of new martensitic stainless steels by two different tribological methods (scratch and dry wear tests) and their comparison to the austenitic standard stainless steel AISI 316L. The scratch test allows obtaining critical loads, scratch friction coefficients, scratch hardness and specific scratch wear rate, and the dry wear test to quantify wear volumes. The damage has been studied by ex situ scanning electron microscopy. Wear resistance was related to the hardness and the microstructure of the studied materials, where martensitic stainless steels exhibit higher scratch wear resistance than the austenitic one, but higher hardness of the martensitic alloys did not give better scratch resistance when comparing with themselves. It has been proved it is possible to evaluate the scratch wear resistance of bulk stainless steels using scratch test. The austenitic material presented lower wear volume than the martensitic ones after the dry wear test due to phase transformation and the hardening during sliding.     

聚合物合金的摩擦磨损特性的研究

作者采用了聚合物共混技术研制了ＰＣ＋ＰＴＦＥ，ＰＣ＋ＰＴＦＥ＋ＰＰＳ两类聚合物合金，并对这些材料的摩擦学特性及其机理进行了研究。结果表明，ＰＴＦＥ的添加不仅可以提高ＰＣ的耐磨性，而且还可降低其摩擦系数；适量的ＰＰＳ的添加具有减摩抗磨作用。聚全物及其合金的摩擦特性可由粘着摩擦理论解释，其磨损过程主要受粘着，磨粒和疲劳机理控制。     

载流下MoS2/Ag纳米复合薄膜摩擦学性能

MoS₂基纳米复合薄膜具有良好的摩擦学性能,但较差的导电性能限制了其在载流条件下作为润滑材料的应用。为提高MoS₂基纳米复合薄膜的导电性能,采用非平衡磁控溅射系统沉积2种不同Ag含量的MoS₂/Ag纳米复合薄膜,并在不同的电流条件下研究MoS₂/Ag纳米复合薄膜与GCr15钢球对摩时的摩擦学性能。结果表明：在载流下2种MoS₂/Ag纳米复合薄膜表现出相似的摩擦性能,而低掺杂MoS₂/Ag薄膜具有更佳的耐磨性能,这归因于低掺杂MoS₂/Ag薄膜具有较好的力学性能;无载流时,MoS₂/Ag纳米复合薄膜在摩擦过程中生成的氧化物颗粒增加了磨损、降低了润滑性,磨损机制主要为磨粒磨损;电流小于0.5 A时,电流促进了转移膜形成,使得摩擦因数降低,但磨损率增加,磨损机制主要为黏着磨损;当电流大于0.5 A时,由于电弧烧蚀加速了薄膜的磨损,磨损机制主要为磨粒磨损、黏着磨损和电弧腐蚀磨损。     

Influence of CrC addition in Ni-Cr-Si-B flame sprayed coatings on microstructure, microhardness and wear behaviour

In the present paper the influence of the addition of chromium carbide (CrC) particles on the microstructure, microhardness and abrasive wear behaviour of flame sprayed Ni-Cr-Si-B coatings deposited on low carbon steel substrate has been reported. Wear behaviour of the coatings was evaluated with a pin-on-block wear system against SiC abrasive medium (120 & 600 grades) over a range of normal load (5–20 N). It was observed that the wear behaviour is governed by the material related parameters (microstructure, microhardness of coating) and test parameters (abrasive grit size and normal load). The addition of CrC reduces the wear rate three to eightfold. Wear resistance was greater against coarse abrasives at high loads than against fine abrasives. Heat treatment of both unmodified (1004) and modified powder (1004-10%CrC, 1004-20%CrC) coatings deteriorated the abrasive wear resistance. SEM study of wear surfaces showed that wear of the coatings largely takes place by groove formation, plowing and scoring. Electron probe micro analysis (EPMA) of the coating was carried out for composition and phase analysis.     

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.     

Effect of Spot Continual Induction Hardening on the Tribological Performance of Grey Cast Iron with Curved Surface

In order to investigate the effect of a spot continual induction hardening (SCIH) process on the tribological performance of grey cast iron with a curved surface, dry sliding wear tests were performed under different loads. The curved surface structure of the workpiece and feed velocity of the inductor were considered important influence factors. X-ray diffractometry (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) were used to investigate the phases, compositions, and morphologies of grey cast iron after the SCIH process and tribological tests. The results showed that the wear mechanism of grey cast iron was always adhesive and abrasive wear at different loads when the workpiece was not strengthened. In the case of partial strengthening, the wear mechanism changed from adhesive and abrasive wear to fatigue–exfoliative wear with increasing load. Oxidative wear always appeared as the dominant wear mechanism when the workpiece was completely strengthened. The wear resistance of the concave surface was always larger than that of the convex surface under the same feed velocity of the inductor. Relatively low feed velocity of the inductor in the SCIH process can optimize the wear resistance of grey cast iron with a curved surface.     

Electrical and tribological properties of composite material with copper matrix reinforced by superelastic hard carbon

Electrical and tribological properties of a copper-based composite material reinforced by superelastic hard carbon particles are studied. Composite material specimens have been produced using the hightemperature pressing of mixtures of copper and fullerene powders. Electrical and tribological reciprocal tests carried out using the plane-on-plane arrangement have shown that the coefficient of friction of the composite material–Ni pair is lower than that of the reference L63 brass–Ni pair at similar values of contact electrical resistance. The abrasive wear resistance of the composite material is 40 times higher than that of brass. The developed copper-based composite materials reinforced by superelastic carbon particles hold promise for use in sliding electrical contacts.     

Principles of abrasive wear

The mechanisms of abrasive wear are reviewed and laboratory test methods assessed. The results of abrasive wear tests on technically pure metals, heat treated steels, cold work hardened materials, hard wear resistant materials and minerals against fixed abrasive grains are discussed. The correlation between abrasive wear resistance and the physical properties of materials is established; the effect of the relative hardness of the abrasive and impact loading is considered. The basic principles of abrasive wear derived are outlined.