Friction coefficient and wear mode transition in micro-scale abrasion tests

The purpose of this work was to conduct ball-cratering wear tests to monitor both normal and tangential forces. Balls of 52100 steel, a specimen of H10 tool steel and an abrasive slurry prepared with silicon carbide particles and distilled water were used. Optical microscopy analysis of the worn craters revealed the presence of only grooving abrasion. However, a more detailed analysis conducted by SEM has indicated that different degrees of rolling abrasion have also occurred along the grooves. The results also showed that the normal force plays an important role in the scattering of the values of the friction coefficient.     

Variations in wear loss with respect to load and sliding speed under dry sand/rubber-wheel abrasion condition: a modeling study

The dry sand/rubber-wheel abrasion tester is widely used to evaluate the low-stress abrasion resistance of materials for the mining/mineral processing industry particularly for the oil sand mining industry. Since wear loss is usually proportional to the applied load, this test is often performed under a fixed load at a fixed sliding speed to rank materials. However, inaccurate or misleading information might be generated under an inadequate load. It has been observed that D2 tool steel exhibits very different responses to variations in the applied load. Above a certain load level, further increase in the applied load may lead to a decrease in wear loss of D2 steel. In order to understand this phenomenon, computer simulation was performed to investigate wear responses of several engineering materials, including D2 tool steel, stainless steel, Al 6061 and Cu 110, to variations in applied load under the dry sand/rubber-wheel abrasion condition. It was demonstrated that the decrease in wear loss of D2 tool steel with an increase in the applied load was attributed to failure of the abrasive sand. Wear losses of the materials with respect to the sliding speed were also investigated. The prediction from the simulation was compared to experimental observations.     

耐磨铸钢在火电厂磨机衬板上的应用研究

为了满足火电厂磨机的安全运行,开发了一种高强度、高韧性低合金耐磨铸钢衬板。该高强度低合金耐磨铸钢以锰、硅为主要合金元素,加入不超过2．0％的铬。不含钼、镍等昂贵合金元素,并加入适量的钛、氮、稀上、钙、镁,改善铸钢的强度和耐磨性,合金总加入量控制在5％以内。热处理后,其基体组织以屿氏体为主,马氏体板条间含有大量纳米级奥氏体薄膜,使材料保持高强度和高硬度的前提下,还具有优良的韧性。着重介绍了耐磨铸钢衬板的微合金化技术、铸造技术和热处理技术,规模化制备了高强度低合金耐磨铸钢衬板,并在火电厂磨机上进行了工业应用。使用考核表明,低合金铸钢衬板在火电厂磨机上使用安全、呵靠,寿命比高锰钢衬板提高160％-210％,而生产成本相当,推广应用具有良好的经济效益和社会效益。     

硬质合金及涂层刀具干铣削高强度钢的磨破损机理研究

采用硬质合金刀片和涂层刀片进行了高强度钢的干铣削试验研究;根据这两种刀片在不同切削用量条件下的磨破损情况,利用扫描电镜和能谱分析的结果,分析了这两种刀片的磨破损机理。     

Scanning electron microscopy observations of worn surfaces of metals in tribological contact with loose solid particles

Surfaces of a 40–60 brass worn by three-body abrasion with SiC grits were observed under the scanning electron microscope. Similar observations were carried out on targets of steel and commercially pure aluminium which had been impacted with hardened steel balls. The brass develops alternating bands of hills and valleys when undergoing three-body abrasion. The hills wear by direct rubbing against the steel counterface. The valleys, however, are embedded with grits which are later removed and probably carry an amount of brass during their departure. The impact process creates craters which show severe deformation. Radial plastic flow of metal also occurs in the target around a crater. It appears that under repeated attack these deformed areas produce wear debris by microspalling. Metal may also be removed by nucleation and propagation of cracks.     

Wear behaviour of hardfaced Fe-Cr-C alloy and austenitic steel under 2-body and 3-body conditions at elevated temperature

Fe-based hardfacing alloys are widely used to protect machinery equipment exposed to different loading situations where abrasives play a dominant role in restricting lifetime of tools. Wear at elevated temperatures is superposed by the effect of oxidation of the wearing surface. In view of the above, two hardfacing alloys based on Fe-Cr-C incorporating Nb, Mo and B to ensure improved performances at elevated temperature were deposited onto mild steel under optimised gas metal arc welding (GMAW) condition. 2-body erosive wear behaviour was evaluated from room temperature up to 650 °C under 30° and 90° impact angle. For 3-body impact/abrasion conditions tests were done with a specially designed cyclic impact abrasion tester (CIAT) at room temperature and 600 °C. The wear behaviour of the hardfacings was compared with austenitic stainless steel. Results indicate that 2-body erosive wear rate of the hardfacing increases with test temperature and with increase in impact angle, whereas wear behaviour of the austenitic stainless steel is non-sensitive to the testing temperature at normal impact. In 3-body impact abrasion testing similar behaviour can be seen; cyclic tests in CIAT at enhanced temperatures result in breaking of coarse carbides, whereas wear mechanisms of the austenitic steel result in massive abrasion and formation of a mechanically mixed layer (MML).     

Abrasion of 0.85% C-Steel under Natural Hawaiian Marine Conditions

A study was undertaken to obtain design data for possible damage scenarios for a planned deep-sea power cable between two Hawaiian islands. The combined results for abrasion and corrosion-erosion of cold drawn 0.85% C-steel armor wire in seawater against seabottom rocks indicate that failure of the proposed design in the desired design life due to these mechanisms is of only intermediate probability. The results also have some general applicability to abrasive wear by and of natural media. The steel and the rock wear simultaneously, with the rock wearing about 150 times faster than the steel. The results can be explained by considering the armor wire as a hard tool causing wear of the rock while abrasion of the steel is caused solely by the hard olivine grains which constitute 6 percent of the rock. Both adjusted wear rates are comparable to laboratory data on abrasion by hard abrasives.     

Some comments on micro‐abrasion interactions of pure metals in bio‐oils

An attempt has been made to study the effect of bio‐oils on the two‐ and three‐body abrasion process of pure metals and steel. The equipment used was a micro‐abrasion tester (TE‐66, Phoenix Tribology (Plint)). The materials considered were mild steel, copper, and aluminium, being the most usable and basic materials for industrial applications such as bearings and gear assemblies. The results were used to identify transitions between wear regimes as a function of sliding speed and load. The effect on the abrasion process in the presence of various lubricant oils was also assessed. The mechanisms of abrasion with and without particles were characterised.     

Abrasion–Corrosion Behaviors of Steel–Steel Contact in Seawater Containing Abrasive Particles

Materials working in slurries containing seawater and abrasive particles degrade gradually because of the synergic effects of mechanical wear and electrochemical corrosion. In this study, the abrasion–corrosion behaviors of a steel–steel tribopair in an environment with artificial seawater and SiO₂/Al₂O₃ particles were investigated. Corrosion is responsible for surface degradation at low concentrations of SiO₂ particles, whereas abrasion is the primary cause for steel damage at high SiO₂ concentrations. When Al₂O₃ particles were used, abrasion was found to be the dominant factor for material loss at all concentrations. Results from this study indicate that at low concentrations of hard particles, abrasion–corrosion behavior is determined by the properties of particles.     

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.     

The abrasive wear of steels in South African soils

A high carbon steel was heat treated to produce a range of microstructures and mechanical properties. These steels were subjected to abrasion testing in stony, clay, and sandy soils. Wear rates were found to be twenty times higher in stony soil than in sandy soil and seven times greater than in clay. It was found that the relative wear resistance increased in sandy and clay soils with increase in steel hardness. In stony soils the relative wear resistance of all steels was found to be similar. An explanation for such behaviour was formulated on the basis of surface temperature heating and work hardening effects. The aggressive nature of abrasion found in stony soils was also found to give rise to the appearance of very hard white layers on the steel surfaces.     

基于ADAMS的支撑辊仿真分析

针对宝钢冷轧厂1500冷轧机组支撑辊磨损问题,分析其产生原因,运用ADAMS对机构进行简化、建模、仿真,并分析各种因素对摩擦力的影响,结果显示,降低钢板运动速度,适当选择钢板张力,提高支撑辊安装精度可减小对支撑辊的磨损。     

Rubber abrasion at steady state

Blade abrasion devices have previously been used to investigate the abrasion resistance of different elastomers. Despite extensive investigation the exact mechanisms that are present during abrasion continue to be the subject of debate. This investigation examines the effect of the normal and frictional forces on the rate and direction of crack growth during the abrasion process. Comparison is drawn between the rates of material loss as measured experimentally on two different styrene butadiene rubber compounds under a range of test conditions. For each set of conditions the representative stored energy release rate is calculated using a finite element analysis technique on a model of a specific abrasion asperity contacting a sliding rigid abrader. It is therefore possible to plot a graph of the stored energy release rate versus crack growth rate for an abrasion process. This is compared with an independently measured cyclic fatigue crack growth rate versus stored energy release rate. The correlation between these two independent tests was excellent. From this work insight into the nature of abrasion is gained.     

港口桥吊用钢丝绳断丝原因分析

港口桥吊用钢丝绳在使用中发生多处断丝现象,通过化学成分分析、力学性能测试、断口分析、金相检验和显微硬度测试等方法对断丝原因进行了分析。结果表明:钢丝绳断丝的性质为疲劳断裂,断裂源位于钢丝表面的损伤或磨损处;断丝表面存在的较多磨损、挤压剥落等缺陷以及断丝显微组织中存在一定数量的铁素体共同导致了钢丝绳中钢丝的早期疲劳断裂。     

Eddy-current and coercive-force testing of abrasion-resistant ball bearing steel IIIX15 subjected to laser and bulk thermal processing

The possibility of using the eddy-current and coercive-force methods for assessment of the structural state and the abrasion resistance of ball-bearing steel IIIX15 (1.00% C and 1.42% Cr) is studied. The steel was subjected to laser and bulk quenching, subzero treatment, and tempering in the temperature range 75–600°C. The presence of residual austenite (in an amount of up to 45 vol %) in the quenched structure is shown to affect the sensitivity of the coercive-force and eddy-current methods used to test the abrasion resistance of steels tempered at low temperatures. Variations in hardness, abrasion resistance, and the parameter of the electromagnetic eddy-current testing as a function of the depth of the laser-irradiated zones in steel IIIX15 subjected to preliminary thermal strengthening is considered.     

两种受电靴材料与不锈钢带电接触摩擦磨损特性的试验研究

在销-盘式摩擦磨损试验机上分别进行了不锈钢／铜基烧结合金材料和不锈钢／铜石墨烧结材料接触的载流摩擦磨损行为的试验研究。在试验中记录了摩擦因数和磨损量的变化,并对磨痕形貌进行了光学显微镜观察。结果显示,电流对2种摩擦副带电接触的摩擦磨损行为有重要的影响。2种材料的摩擦因数随电流的增大而呈现截然相反的变化趋势,但两者的磨损量却随电流的增加而增大。不锈钢／铜基烧结合金材料的磨损机制主要是粘着磨损及氧化磨损。不锈钢／铜石墨烧结材料磨损机制包括磨粒、粘着磨损和电弧烧蚀,其中电弧烧蚀对磨损量的影响随电流的增大而增加。     

直缝钢管轧机成形辊的失效分析

介绍对直缝钢管冷轧机的成形辊进行失效分析的过程。针对成形辊的服役环境，这里对成形辊的开裂和磨损原因进行了分析，认为成形辊与管坯相对滑动而引起的摩擦磨损、成形辊表面被反复加热和冷却而引起的热疲劳是引起成形辊磨损的主要原因。认为裂纹是由热应力引起的热疲劳开裂，从理论上推算热应力的大小，并分析其使工件热疲劳破坏的可能性，这里还将在提高成形辊寿命方面作一些探讨     

Strain Hardening: Can it Affect Abrasion Resistance?

It has been largely reported in the literature that previous strain hardening has none or negligible effect on abrasive wear resistance. Those results are mainly obtained using sand rubber wheel tests and pin-on-disk tests, and have been attributed to the large strain hardening promoted by the abrasion phenomena themselves. The stresses involved in those tests are very high and the stress distributions spread toward subsurface regions at large depths. This work investigates the effects of strain hardening on low-severity (low stress at low depth) abrasive wear resistance. Microabrasion tests, normally regarded as lower stress tests, were used in order to impose low severity. Two types of stainless steels were tested: an austenitic AISI 304 steel and a ferritic AISI 430 steel. Strain hardening was obtained via thickness reduction (20%) of stainless steel sheets in a laboratory cold rolling mill. The microabrasion wear tests were carried out in a fixed-ball microabrasion tester with a three-axis load cell to continuously and simultaneously monitor the forces involved in the tests. Contrary to many findings so far in the literature, previous strain hardening increased abrasion wear resistance (55 and 63%, respectively) for both materials. Hertz calculations, simulations using Finite Element Program with explicit solution, conventional mechanical tests, microhardness profiles, microstructural analysis, and X-ray diffraction analysis were used to explain this paradigm shift for the case of microabrasion tests.     

The effect of microstructure and wear conditions on the wear resistance of steel metal matrix composites fabricated with PTA alloying technique

The concept of hard particles in a softer metal matrix has long appealed to number of industries dealing among others with drilling and mining. For these facilities, the PTA (Plasma Transferred Arc) alloying technique is advisable and advantageous for several reasons; the equipment may be portable and moved near the working site, the treatment may be applied strictly to the area where the wear problem is situated and after the treatment little machining is required. Four different coatings are tested against three different modes of wear occurring either alone or less frequently combined in this kind of applications, i.e. adhesion, low stress abrasion and two-body abrasion. Two of the coatings examined belong to the category of tool steels with very hard carbides in their microstructure, namely TiC, M₂C and M₆C. The other two are boride coatings belonging to the Fe–B and Fe–Cr–B system respectively. A heat treated AISI D2 tool steel commonly used in this type of applications is also examined for comparison. Fe–Cr–B coating performance is at least 2 times better in low stress and two-body abrasion and four orders of magnitude better in adhesion wear than the AISI D2 tool steel. Fe–B coating can be used in pure adhesion or abrasion situations, but their brittleness forbids their use in situations involving impact loading. AISI M2 coating presents similar wear performance with AISI D2 tool steel in abrasion, whereas in adhesion wear it performs at least two orders of magnitude better. MMC–TiC coating has good performance in pure two-body abrasion situations due to the presence of the very hard TiC particles in its microstructure.     

Wear of low temperature nitrided steels under different wear processes

A programme of tests has been carried out to assess the wear resistance of three low temperature nitriding treatments when compared with the untreatedv steel and a standard cyanide case-hardening treatment, under conditions of scuffing, abrasion, fretting and corrosion. The main conclusion is that low temperature nitriding is most suited to applications where scuffing and corrosion are the main wear mechanisms and that the resistance to abrasion and fretting is poorer in general than that of traditional case-hardening. Therefore, care should be taken in assessing the wear process in any application in which these treatments are used. Reference is also made to the wear mechanisms in the different tests.