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.     

High stress abrasive wear behaviour of aluminium hard particle composites: Effect of experimental parameters, particle size and volume fraction

High stress abrasive wear behaviour of aluminium alloy (ADC-12)–SiC particle reinforced composites has been studied as a function of applied load, reinforcement size and volume fraction, and has been compared with that of the matrix alloy. Two different size ranges (25–50 and 50–80 μm) of SiC particles have been used for synthesizing ADC-12–SiC composite. The volume fraction of SiC particles has been varied in the ranges from 5 to 15 wt%. It has been noted that the abrasive wear rate of the alloy reduced considerably due to addition of SiC particle and the wear rate of composite decreases linearly with increase in SiC content. It has also been noted that the wear resistance of composite varies inversely with square of the reinforcement size. The wear rate of the alloy and composite has been found to be a linear function of applied load but invariant to the abrasive size; at critical abrasive size, transition in wear behaviour is noted. This has been explained through analytically derived equations and wear–surface examination.     

Effects of particle size, polishing pad and contact pressure in free abrasive polishing

The objective of this research is to better understand the mechanisms of material removal in the free abrasive polishing process. Experiments were carried out to understand the effects of particle size, polishing pad and nominal contact pressure on the wear rate and surface roughness of the polished surface. A theoretical model was developed to predict the relationship between the polishing parameters and the wear rate for the case of hard abrasive particles sandwiched between a soft pad and a workpiece (softer than the abrasive particles). Experimental results and theoretical predictions indicate that the wear rate increases with an increase in particle size, hardness of polishing pad and nominal contact pressure, and with a decrease in elastic modulus of the polishing pad. Surface roughness increases with an increase in particle size and hardness of polishing pad, and nominal contact pressure has little effect on the roughness. A dimensionless parameter, wear index which combines all of the preceding parameters, was introduced to give a semi-quantitative prediction for the wear rate in free abrasive polishing. It is also suggested that when polishing hard material, in order to achieve a high materials removal rate and a smooth surface, it is preferable to use diamond as the polishing particles because of their high deformation resistance.     

Three-body abrasive wear with small size diamond abrasives

Three-body abrasive wear rate was measured as a function of abrasive size and applied load using molybdenum alloy spheres of diameter 25.4 mm as test specimens. Diamond abrasives in the size range 1–60 μm normally used for metal lapping were tested. Tests were conducted at lap loads ranging from 9.8 to 107.9 N. For a given load it was found that there is a maximum abrasive size beyond which the wear rate will not increase and may even decrease. Several explanations of this critical size effect reported in the literature were evaluated on the basis of physical evidence.Wear rate generally increases linearly with increasing load. However, this did not occur with small abrasives. This deviation from linearity was found to be the result of an unusually effective abrasive wear condition. An explanation of this effect is given.     

Wear study of Ni–WC composite coating modified with CeO2

In the present investigation, Ni–WC composite powder was modified with the addition of CeO₂ in order to form a new composition of Ni–WC–CeO₂. The Ni–WC and Ni–WC–CeO₂ compositions were used for coating deposition by high-velocity oxy-fuel (HVOF) spraying process so as to study the effect of CeO₂ addition on microstructure, distribution of various elements, hardness, formation of new phases, and abrasive wear behavior. Further, the effect of load, abrasive size, sliding distance, and temperature on abrasive wear behavior of these HVOF-sprayed coatings was investigated by response surface methodology. To investigate the abrasive wear behavior of HVOF-sprayed coatings four factors such as load, abrasive size (size in micrometers), sliding distance (meters), and temperature (°C) with three levels of each factor were investigated. Analysis of variance was carried out to determine the significant factors and interactions. Investigation showed that the load, abrasive size, and sliding distance were the main significant factors while load and abrasive size, load and sliding distance, abrasive size and sliding distance were the main significant interactions. Thus an abrasive wear model was developed in terms of main factors and their significant interactions. The validity of the model was evaluated by conducting experiments under different wear conditions. A comparison of modeled and experimental results showed 4–9% error. The abrasive wear resistance of coatings increases with the addition of CeO₂. This is due to increase in hardness with the addition of CeO₂ in Ni–WC coatings.     

Wear resistance of rolling-ball bearings operating in an abrasive medium

The article is devoted to calculating the wear rate of elements of rolling-ball bearings operating in an abrasive medium. Based on the obtained analytical dependence and calculated data for the wear rate, it can be concluded that an increase in the size and concentration of abrasive particles in oil, as well as an increase in the angle of the ring misalignment, increase the wear rate of bearing elements, whereas with an increasing coefficient of relative elongation and material hardness, the wear rate of the bearing elements decreases.     

磨屑对润滑油摩擦性能的影响

通过实验和模拟研究磨粒对润滑油摩擦性能的影响。首先通过微纳米压/划痕试验测量含磨屑润滑油的摩擦因数。同时,建立边界润滑体系模型,采用分子动力学方法模拟含磨屑润滑油膜在不同载荷下沿膜厚方向的压缩率和密度分布;对体系的上下固体壁面施加方向相反的剪切速度,计算出壁面原子的应力、摩擦力、正压力和摩擦因数;分析不同粒径磨屑的动态行为特征;通过减少润滑油分子数量,探究乏油工况下含磨屑润滑体系的摩擦性能。结果表明,润滑体系摩擦因数的模拟值与试验值一致;磨屑的存在会降低油膜的压缩率,同时在高载下磨屑的存在会对油膜的分层产生破坏,影响磨屑附近的密度分布;含小粒径磨屑的润滑体系的摩擦因数比含大粒径磨屑的润滑体系的小,表明磨粒聚集长大现象会恶化润滑油的润滑性能;磨屑在剪切过程中同时存在滚动和滑动,含小粒径磨屑的润滑体系剪切过程中表现出波动幅度更大的角速度;随着载荷的增大,磨屑角速度减小,波动幅度降低;在乏油工况下,磨屑会在剪切过程中出现变形破碎现象。     

An AFM study of single-contact abrasive wear: The Rabinowicz wear equation revisited

A nanoscale study of the abrasive wear behaviour of a ductile monophasic metallic alloy (the stainless steel AISI 316L) is presented. By using atomic force microscopy (AFM) based techniques, particularly a diamond tip mounted on a stiff steel cantilever, the contact of a single abrasive asperity was simulated, and it was possible to determine accurately the load threshold below which no measurable wear occurs. It was observed that, once this nanoscale threshold for wear is overcome, the worn volume increases linearly with the load, as predicted by the Rabinowicz model. However, it was found that, although this critical threshold for measurable wear is most certainly related with the yield-onset of plastic deformation, it cannot be predicted by using directly a criterion based on the bulk microhardness. Hence, the results presented in this paper strongly indicate that indentation size effects play a crucial role on the response to abrasive wear at the asperity contact level.     

The wear rate of n-type Si(100)

Single-crystal Si(100) (n type) was scratched at room temperature by a single-point 90° pyramidal diamond in each of the following fluids: reagent-grade absolute ethanol, methanol, acetone and deionized water. The wear rate in each case was determined from a measurement of the cross-sectional areas of circular multiscratch grooves and the increase in this area with scratching time. These areas vary as the contact force on the diamond and the fluid covering the silicon surface during the scratching test vary. As expected, the wear rate depended on the force (dead-weight load) on the diamond (the wear rate increased as the force was increased) but fluids also had a significant effect on the wear. The wear rate of silicon scratched in ethanol is twice that in deionized water when the dead-weight load on the diamond is 0.49 N and all other experimental variables are held constant. These results were compared with two models of abrasive wear of ceramic materials.     

Abrasive wear behavior of thermally sprayed diamond reinforced composite coating deposited with both oxy-acetylene and HVOF techniques

Diamond and diamond-based coatings have long been studied for their exceptional properties. Although a great deal of research has been carried out in this field, little is known about their tribological wear behavior. In the present work, diamond reinforced composite (DRC) coatings of varying diamond content was deposited on mild steel substrates using both oxy-acetylene (OA) and high velocity oxy fuel (HVOF) thermal spraying techniques. The high stress abrasive wear behavior of these coatings is studied by performing two body abrasion tests for varying experimental parameters. It is observed that the HVOF-sprayed coatings suffered abrasion at a relatively low wear rate. The reasons for variations observed in the wear rate as a function of displacement during abrasion and grit size could be attributed to the deterioration of abrasive particles and the particle size effect respectively. While the disparity in the wear rates with respect to composition of the coatings was primarily controlled by the diamond content in the coating. The abrasive wear mechanism was found to be the same in both the coatings except that the coating deposited by HVOF spray technique, offered better abrasion resistance and therefore abraded at a slower rate. This is possibly due to lower porosity in the coating and higher bond strength between reinforced diamond particulates and the bronze matrix in HVOF-sprayed specimens.     

A micro-contact and wear model for chemical–mechanical polishing of silicon wafers

A micro-contact and wear model for chemical–mechanical polishing (CMP) of silicon wafers is presented in this paper. The model is developed on the basis of elastic–plastic micro-contact mechanics and abrasive wear theory. The synergetic effects of mechanical and chemical actions are formulated into the model. A close-form equation of material removal rate from the wafer surface is derived relating to the material, geometric, chemical and operating parameters in a CMP process. The model is evaluated by comparing the theoretical removal rates with those experimentally determined. Good agreement is obtained for both chemically active and inactive polishing processes. The model reveals some insights into the micro-contact and wear mechanisms of the CMP process. It suggests that the removal rate is sensitive to the particle concentration in the slurry, more sensitive to the applied load and operating speed and most sensitive to the surface hardness and slurry particle size. The model may be used to study the effects of different materials, geometry, slurry chemistry and operating conditions on CMP processes.     

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.     

Influence of abrasive grain geometry on friction coefficient and wear rate in belt finishing

We focus our study on belt finishing process using a 3D model with multi-asperity abrasive wear on real rough surfaces. The established model allows determining the effect of the local geometry of abrasive grain on the friction coefficient and wear rate. This study shows that the friction coefficient and wear rate increase with the local slopes of the roughness. With the increase of the macroscopic normal load, the wear rate increases rapidly. Such effect is related to the increase of the cutting force of each grain leading to the transition in dominant wear mode from ploughing to wedging and cutting.     

Ti6A14V的微磨粒磨损研究

研究了医用Ti6A14V合金在蒸馏水中的微磨粒磨损行为，考察了载荷、滑行距离、料浆浓度和转速对微磨粒磨损规律的影响，并对微磨粒磨损机制进行了讨论。结果表明：随载荷、滑行距离和料浆浓度的增加，Ti6A14V合金的磨损量增加，磨损机制由三体磨损转变为混合磨损。     

Tribological Behaviors of Self-lubricating Coating Prepared by Electrospark Deposition

Cu/h-BN self-lubricating coating was prepared on AISI1045 steel by electrospark deposition. The friction coefficient and wear rates were measured using the ball-on-disk method, and the tribological behaviors were discussed. Results showed that the friction coefficient decreased with an increase in sliding speed and load. The wear rate decreased with an increase in sliding speed and increased with an increase in load. The self-lubricating coating exhibited much lower friction coefficient and wear rate than the uncoated mild steel under the test condition. SEM micrographs show that the main wear mechanisms of the self-lubricating coating are abrasive wear and fatigue wear.     

Diamond particle shape: Its measurement and influence in abrasive wear

The classification of diamond particles in terms of their abrasive characteristics is addressed in this work. Specifically, diamond particles of different grades have been studied in terms of their shape to identify useful trends and correlations with experimental wear rate. Ten diamond types, typically used by the abrasives industry and exhibiting varied shape, were selected. They included highly geometric single crystals, crushed single crystals, and polycrystalline diamond particles, with nominal diameters of between 65 and 197 μm. Electronic boundary projections were obtained using a digital-camera-equipped optical microscope, which were then processed using proprietary software. The parameters calculated include: diameter (minimum, minor and maximum), aspect ratio, convexity and sharpness. Interesting correlations were found between convexity and sharpness that engendered both these parameters to be considered as useful measures of wear rate. This was reinforced by experimental wear tests, using grinding wheels manufactured from six of the 10 diamond types, which demonstrated excellent correlations of sharpness (0.991 correlation coefficient), and convexity (0.987 correlation coefficient), with the wear rate of a polyurethane workpiece.     

挤压型不锈钢向心关节轴承的摩擦磨损性能

研究挤压型不锈钢向心关节轴承在不同的试验参数下的摩擦磨损性能,分析其摩擦磨损形式。结果表明:不锈钢向心关节轴承的磨损形式以黏着磨损和磨粒磨损为主,磨损量随载荷的增大而增大,随摆动频率先减小而后增大;摩擦因数随载荷和摆动频率的增大而减小。     

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.     

Some observations on two-body abrasive wear

Pin-on-disc-type two-body abrasion tests were carried out on five metals with seven particle sizes over a range of loads, lengths of travel and sliding speeds. The familiar results that two-body abrasive wear is proportional to load and to distance travelled were confirmed. The “size effect”, in which particles below about 100 μm produce progressively less wear, was shown to be independent of load, sliding speed and prior cold working. Increasing the sliding speed from 1 to about 100 mm s^?1 produced an increase in wear resistance of about 50% for AISI 1020 steel. An increase in velocity above 100 mm s^?1 had little effect on the wear resistance. Plots of the wear resistance against the hardness of the annealed metal showed significant deviations from the linear relationship reported in the literature. The result is influenced by both sliding velocity and particle size.     

Two-body abrasion of some polymers against 6–50 μm SiC abrasives

Single- and multiple-pass two-body abrasion tests were run on Nylon $\text{6}\text{6}\text{+ 20\%}$ polytetrafluoroethylene (PTFE) and polycarbonate + 10% PTFE sliding dry against 6–50 μm SiC abrasives. A functional relationship was developed between the single-pass wear rate and the abrasive particle size for abrasive particle sizes less than or equal to 10.4 μm. The single-pass abrasive wear rate was 20–40 times greater than the multiple-pass wear rate for each material when it was slid against abrasive grains with a mean size not exceeding 10.4 μm. This was due to the formation of loose polymer fibril wear debris in single-pass sliding and of transferred plateaux of polymer in multiple-pass sliding. The rate of increase in wear with particle size was about 20 times greater for single-pass sliding than for multiple-pass sliding. Above a mean abrasive particle size of 10.4 μm the type of mechanism in both single-pass and multiple-pass sliding was that of ploughing.