Major Wear Mechanisms Research Articles

Effects of High Temperature Wear Behaviour of Sintered Ti–6Al–4V Reinforced with Nano B4C Particle

The present work deals with improving the high temperature wear behavior of sintered Ti–6Al–4V reinforced with nano B4C with the help of mechanical alloying method. By using Pin-on-disc wear testing machine, the high temperature wear behavior of the prepared composites were investigated at an applied load of 10–30 N with an increment of 5 N for various pin temperatures (30, 50, 100 and 150 °C). The wear resistance of the Ti–6Al–4V increased with increase in the wt% of the nano B4C reinforced at all temperatures and sliding distances. The transition of severe to mild wear strongly depended on the addition of nano B4C particles. Ti–6Al–4V showed a severe wear at all conditions such as sliding distances and sliding temperatures. But with the addition of 2 to 10 wt% of nano B4C particles, the severe to mild wear was noticed at all temperature conditions. The wear surface of the transition mode was evaluated by scanning electron microscope. At elevated temperature, the major wear mechanism for the Ti–6Al–4V was adhesion, whereas Ti–6Al–4V–B4C composite showed abrasion, oxidation and delamination as the foremost wear mechanisms.

Study of surface roughness and flank wear in hard turning of AISI 4140 steel with coated ceramic inserts

This experimental investigation deals with dry hard turning of AISI 4140 steel using PVD-TiN coated Al2O3+TiCN mixed ceramic inserts. The combined effect of cutting parameters (cutting speed, feed and depth of cut) on performance characteristics such as surface roughness and flank wear is explored by Full factorial design (FFD) and analysis of variance (ANOVA). The results show that feed is the principal cutting parameter influencing surface roughness, followed by cutting speed. However, flank wear is affected by the cutting speed and interaction of feed-depth of cut, although depth of cut has not been found statistically significant, but flank wear is an increasing function of depth of cut. Observations are made on the machined surface, and worn tool by Scanning electron microscope (SEM) to establish the process. Abrasion was the major wear mechanism found during hard turning within the studied range. The effect of tool wear on surface roughness was also studied. The experimental data were analyzed to predict the optimal range of surface roughness and flank wear. Based on Response surface methodology (RSM), mathematical models were developed for surface roughness (Ra) and flank wear (VB) with 95% confidence level. Finally, under optimum cutting conditions (obtained by response optimization technique), tool life was evaluated to perform cost analysis for justifying the economic viability of coated ceramic inserts in hard turning. The estimated machining cost per part for TiN coated ceramic was found to be lower (Rs. 12.31) because of higher tool life (51 min), which results in the reduction of downtime and increase in savings.

Wear mechanism for spray deposited Al-Si/SiCp composites under dry sliding condition

Al-Si/15%SiCp (volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy (OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10–220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.

Design and analysis of engine timing silent chain system

Based on the meshing principle of silent chain and the structure of an automobile engine, timing silent chain system including involute tooth sprocket, guide plate, tension plate, and silent chain is designed in this paper. Dynamics analysis model is built, and vibration of the chain system is studied. The link tensile force and the contact force between link and other components, and the transmission error of crankshaft sprocket and exhaust camshaft sprocket are analyzed. The design and analysis method of the timing silent chain system is proposed. The wear elongation of the timing silent chain system is studied through the road test. The wear morphology of the link plate and pin working surface are observed. Analysis results show that the design method of the timing silent chain system is feasible. The major wear mechanism of the pin is fatigue wear, and the major wear mechanism of the link plate is fatigue wear and abrasive wear. The results of the dynamic simulation and the experimental research show that the design and analysis method of timing silent chain system is scientific and feasible, and wear resistant of the timing silent chain system is high.

Improving the Wear Resistance of Aluminum Fly Ash Composites by Multipass Friction Stir Processing

In this study, the multi-pass friction stir processing (MP-FSP) technique was performed on ADC6 aluminum alloy + 5 wt% fly ash composite (A5FC) castings to increase their surface area. The dry sliding wear behaviors of the ADC6 alloy, A5FCs, and MP-FSPed A5FCs were evaluated. Dry sliding wear tests were performed using a ring-on-washer machine at a constant rotation speed of 100 rpm for 60 min, and the normal load was 10, 20, 30, and 40 N. The results showed that the MP-FSPed A5FCs had the lowest wear rates in the load range from 10 to 40 N, and adhesive wear was the major wear mechanism in these tests. The increased wear resistance was mainly due to grain refinement and elimination of casting defects after subjecting the ash composite to MP-FSP. The microstructure of the MP-FSPed A5FCs reveals that the sizes of the added raw fly ash particles decreased from micro-to nanoscale levels, and the nanoscale fly ash was uniformly dispersed in the aluminum matrix.

Experimental investigation into machinability of hardened AISI 4140 steel using TiN coated ceramic tool

The concerns with some machinability aspects on surface roughness, flank wear and chip morphology in hard turning of AISI 4140 steel using PVD-TiN coated Al2O3+TiCN mixed ceramic inserts under dry environment. The machined surface characterization, tool wear mechanism and chip morphology are investigated in this study, along with optimization and development of mathematical models for surface roughness and flank wear. By adopting combined techniques such as orthogonal array and analysis of variance, the consequences of cutting parameters (cutting speed, feed and depth of cut) on surface roughness (Ra, Rq and Rz) and flank wear (VB) are explored. The results show that feed is the principal cutting parameter influencing surface roughness, followed by cutting speed. However, flank wear is affected by the cutting speed and interaction of feed-depth of cut, although depth of cut has not been found statistical significant, but the flank wear is an increasing function of depth of cut. Thereafter, observations are made on the machined surface, worn tool and the generated chips by scanning electron microscope (SEM) to establish the process. Abrasion was the major wear mechanism found during hard turning within the studied range. Chip morphology indicates the formation saw-tooth/serrated chips at higher feed due to reduction of chip thickness, results in degradation of surface finish. Additionally, effect of tool wear on surface roughness has been studied. The experimental data were further analyzed to predict the optimal range of surface roughness and flank wear. Finally, based on response surface methodology (RSM) mathematical models are developed for surface roughness (Ra, Rq and Rz) and flank wear (VB) with 95% confidence level. Effectiveness, adequacy, statistical significance and validity, and fit of data of the developed model has been checked using ANOVA analysis (depending on P value, F value and R2 value), Anderson–Darling test and normal probability plot. The proposed experimental and statistical techniques initiate authentic methodologies to optimize, model and improve the hard turning process, which can be prolonged effectively to analyse other machining processes.

부품 및 벤치 실험을 통한 폴리우레탄 유압 왕복 실의 가속 실험

Hydraulic reciprocating seals have been widely used to prevent fluid leakage and to provide lubricant film on counter surface in various hydraulic system. The degradation of the seal may cause the catastrophic failure of the hydraulic system. To assess the durability of the seals and the compatibility with counter surface, accelerated life testing (ALT) has been typically employed from industry. However, ALT often takes up to a few months to cause a failure of the seals, and therefore, there is a need to develop more efficient ALT methods. In this work, the degradation characteristics of polyurethane (PU) seals from field test are investigated and they are compared to those from the component and bench tests, with an aim to contribute to the development of ALT method. From the comparison of the cross-sectional profiles of the sealing surface of the PU specimens before and after the tests, both wear and compression set are found to be responsible for degradation of the PU seals. It is also shown that the major wear mechanisms of the PU seals from the field is abrasive wear and formation of pits. The component and bench tests performed in this work are shown to reproduce such wear mechanisms, and therefore, those test methods can be used as an ALT method for PU seals. In particular, the bench test proposed in this work may be effectively utilized to assess the durability and the compatibility of the seals with the counter surface. The results of this work are expected to aid in the design of ALT for PU seal.

Effects of photoaging on the tribological properties of engineering plastics

Ball‐on‐disk tests were performed to investigate the effects of photoaging on the tribological properties of engineering plastics under dry sliding. Results exhibit that different molecular structures of plastics result in different aging morphologies, and ultra high molecular weight polyethylene has better resistance to photoaging than polyformaldehyde (POM). However, POM has better wear resistance before and after the photoaging. Marked increase of the width and depth of wear tracks is observed after aging. Analysis of worn surface has revealed that photoaging significantly affects the wear mechanism of ultra high molecular weight polyethylene and POM. Although the major wear mechanism before the aging of materials is identified as plastic deformation and adhesive wear, it becomes quite complicated when the materials experienced photoaging. Such complex wear mechanism hence deteriorates the tribological performance of the engineering plastics. Copyright © 2014 John Wiley & Sons, Ltd.

Tribological and corrosion properties of Al–12Si produced by selective laser melting

Abstract

Fretting wear of Mg–Li–Al based alloys

The fretting wear behavior of newly developed Mg–Li–Al based alloys LAT971 and LATZ9531 is investigated by using reciprocating fretting wear testing under dry condition with varying number of cycles (10–104), normal load (1–10N), oscillation frequency (1–9Hz), and displacement amplitude (80–200µm). The worn surface is characterized by scanning electron microscopy to reveal wear mechanisms governing under each condition. Overall, results show that LATZ9531 elicits consistent performance, lower coefficient of friction (~0.50) than conventional AZ31 (~0.69) and LAT971 (0.60). But, under the condition of high normal load (of 10N), LAT971 shows least wear volume loss (~0.05mm3) as well as lower coefficient of friction (~0.26) compared to that of LATZ9531 or conventional AZ31. In addition to central cracking in LATZ9531, mainly adhesive and delamination wear mechanism are noticed. Under frequency variation LAT971 shows enhanced performance especially at high frequency (~9Hz). However, with increase in slip amplitude (~200μm), the major wear mechanism is observed to be abrasive and oxidative wear, wherein LATZ9531 shows least wear volume. Friction hysteresis of increasing slip amplitude shows increase in energy consumption during fretting wear, and its shape confirms that in spite of change in stroke lengths, fretting is occurring in the gross slip regime.

Diffusion and Oxidation Wear of Superhard Cutting Tool Based on Thermodynamics Enthalpy

Cutting temperature always highly reaches over to 1000°C? when high speed machining with PCBN tools. Diffusion of tool material element may have important influence on tool wear at such high temperature, the diffusion wear and oxidation wear have become the major wear mechanism. In this paper, the rules of diffusion wear and oxidation wear for PCBN cutting tools are proposed and analyzed based on thermodynamics theory. Dissolution concentrations in typical normal workpice materials of PCBN tool material at different temperature are then calculated. Diffusion reaction rules in high temperature are developed and analyzed using Gibbs free energy criterion. The machining tests were conducted using the PCBN tools at different cutting speeds of 50, 95,100 and 180 m/min, feed of 0.1, 0.2 and depth of cut of 0.1, 0.8, 1, and 1.5 mm respectively on PUMA300LM numerically-controlled lathe. It was found that the theoretical results were uniform with the experimental data; the results will provide useful references for tool material design and selection.

Wear damage of cemented carbides with different combinations of WC mean grain size and Co content. Part II: Laboratory performance tests on rock cutting and drilling

In the present work we carried out laboratory performance tests of cemented carbides with very different WC grain sizes varying from nearly 0.2μm to 5μm and Co contents varying from 6 to 33wt.% in rock cutting and drilling. These tests are determined to well simulate the real operation of cemented carbides in mining and construction applications, particularly in road-planing and rock-cutting as well as in percussive drilling and rotary drilling. The major objective of the present work was to examine the wear damage, wear behavior and wear mechanisms of cemented carbides having a similar hardness but greatly varying with respect to their WC mean grain size and Co content in rock evacuation.Phenomena of micro-fatigue, micro-fracturing and micro-chipping of cemented carbides are found to play the decisive role in rock-cutting. As a result, the wear-resistance of the near-nano carbides having a reduced fracture resistance is significantly lower than that of the medium and coarse grades having similar hardness values. The major wear mechanism of the near-nano grade in rock-cutting is related to micro-cracking and micro-chipping leading to the detachment of huge WC–Co agglomerates. This is presumably a result of reduced fracture toughness of the near-nano cemented carbides containing much grain growth inhibitors, which is caused by the segregation of grain growth inhibitors at the WC–Co and WC–WC interfaces. In contrast to the near-nano grades, the major wear mechanism of the coarse grade in rock-cutting is related to wearing off the binder interlayers among the large WC grains and their micro-chipping and fragmentation.Phenomena of micro-fatigue, micro-fracturing and micro-chipping of cemented carbides also play a very important role in rock-drilling. The wear-resistance of the near-nano grade is noticeably lower than that of the corresponding straight coarse-grain grade having nearly the same hardness but significantly higher fracture resistance. As in the case of rock-cutting, the major wear mechanism of the near-nano grade in rock-drilling is related to micro-cracking and micro-chipping caused by micro-fatigue phenomena, which leads to the detachment of huge WC–Co agglomerates. In contrast to that, the following wear mechanisms take place on the surface of the medium and medium-coarse grades during percussive drilling: (1) wearing the binder among WC grains, which leaves them unsupported, (2) abrasion of the surface of the WC grains, (3) micro-chipping the WC grains, (4) detachment of separate WC grains, and (5) detachment of relatively small WC–Co fragments. There are some regions on the worn surface of the medium and medium-coarse grades, where the WC grains were presumably in direct contact with the rock during drilling (first regions), and there are some regions lying slightly below the first regions (second regions). The worn surfaces in the first regions are characterized by a significantly lower Co content (less than 1wt.%) than on average. The Co contents on the surface of the second regions, which were not presumably in direct contact with the rock when drilling, are noticeably greater and even slightly higher than the average Co content in the bulk of the medium and medium-coarse grades, therefore, the binder was not predominately worn out from the carbide surface in these regions. The second regions presumably comprise Co interlayers on the surface on underlying WC grains after the detachment of WC–Co fragments due to micro-fatigue, as there are no traces of abrasive wear on their surface. Therefore, the presence of the first and the second region on the worn surface with various Co contents is a clear indication of the completely different wear mechanisms in these two regions.

Diffusion and Oxidation Wear of Superhard Cutting Tool Based on Thermodynamics

Cutting temperature always highly reaches over to 1000°C when high speed machining with PCBN tools. Diffusion of tool material element may have important influence on tool wear at such high temperature, the diffusion wear and oxidation wear have become the major wear mechanism. In this paper, the rules of diffusion wear and oxidation wear for PCBN cutting tools are proposed and analyzed based on thermodynamics theory. Dissolution concentrations in typical normal workpice materials of PCBN tool material at different temperature are then calculated. Diffusion reaction rules in high temperature are developed and analyzed using Gibbs free energy criterion. The machining tests were conducted using the PCBN tools at different cutting speeds of 50, 95,100 and 180 m/min, feed of 0.1, 0.2 and depth of cut of 0.1, 0.8, 1, and 1.5 mm respectively on PUMA300LM numerically-controlled lathe. It was found that the theoretical results were uniform with the experimental data; the results will provide useful references for tool material design and selection.

Diffusion and Oxidation Wear of PCBN Tool when Cutting Materials Difficult-to-Cut Based on Thermodynamics

Cutting temperature always highly reaches over to 1000°C when high speed machining with PCBN tools. Diffusion of tool material element may have important influence on tool wear at such high temperature, the diffusion wear and oxidation wear have become the major wear mechanism. In this paper, the rules of diffusion wear and oxidation wear for PCBN cutting tools are proposed and analyzed based on thermodynamics theory. Dissolution concentrations in typical normal workpice materials of PCBN tool material at different temperature are then calculated. Diffusion reaction rules in high temperature are developed and analyzed using Gibbs free energy criterion. The machining tests were conducted using the PCBN tools at different cutting speeds of 50, 95,100 and 180 m/min, feed of 0.1, 0.2 and depth of cut of 0.1, 0.8, 1, and 1.5 mm respectively on PUMA300LM numerically-controlled lathe. It was found that the theoretical results were uniform with the experimental data; the results will provide useful references for tool material design and selection.

Diffusion and Oxidation Wear of Superhard Cutting Tool Based on Thermodynamics Solubility

Cutting temperature always highly reaches over to 1000°C? when high speed machining with PCBN tools. Diffusion of tool material element may have important influence on tool wear at such high temperature, the diffusion wear and oxidation wear have become the major wear mechanism. In this paper, the rules of diffusion wear and oxidation wear for PCBN cutting tools are proposed and analyzed based on thermodynamics theory. Dissolution concentrations in typical normal workpiece materials of PCBN tool material at different temperature are then calculated. Diffusion reaction rules in high temperature are developed and analyzed using Gibbs free energy criterion. The machining tests were conducted using the PCBN tools at different cutting speeds of 50, 95,100 and 180 m/min, feed of 0.1, 0.2 and depth of cut of 0.1, 0.8, 1, and 1.5 mm respectively on PUMA300LM numerically-controlled lathe. It was found that the theoretical results were uniform with the experimental data; the results will provide useful references for tool material design and selection.

Diffusion Wear of PCBN Tool when Cutting Materials Difficult-to-Cut Based on Thermodynamics

Cutting temperature always highly reaches over to 1000°C when high speed machining with PCBN tools. Diffusion of tool material element may have important influence on tool wear at such high temperature, the diffusion wear and oxidation wear have become the major wear mechanism. In this paper, the rules of diffusion wear and oxidation wear for PCBN cutting tools are proposed and analyzed based on thermodynamics theory. Dissolution concentrations in typical normal workpice materials of PCBN tool material at different temperature are then calculated. Diffusion reaction rules in high temperature are developed and analyzed using Gibbs free energy criterion. The machining tests were conducted using the PCBN tools at different cutting speeds of 50, 95,100 and 180 m/min, feed of 0.1, 0.2 and depth of cut of 0.1, 0.8, 1, and 1.5 mm respectively on PUMA300LM numerically-controlled lathe. It was found that the theoretical results were uniform with the experimental data; the results will provide useful references for tool material design and selection.

Wear performance of spark plasma sintered Co/WC and cBN/Co/WC composites

The present study investigates the efficiency of spark plasma sintering (SPS) technique on the tribological behavior of tungsten carbide composites, and aims to develop the wear resistance of these composites by addition of cubic boron nitride (cBN). Wear tests of spark plasma sintered 6(wt.%)Co/WC, 25(vol%)cBN/6Co/WC and conventionally fabricated 6(wt.%)Co/WC as a reference sample were performed by ball-on-disk contact with dry and rotational sliding at room temperature in order to determine the friction coefficient and wear rate. Wear mechanisms were explained by using SEM observations and the wear rates were computed by a surface profilometer. In all cases, the major wear mechanisms were observed gradually in the form of microcraking, material removal by grain pull out, and generation and spalling of a tribochemical layer. Based on the experimental results, the addition of cBN considerably enhanced the wear resistance of tungsten carbides. In addition, these results revealed that SPS process has outstanding potential for the fabrication of tungsten carbides with high wear properties for tribological applications.

Diffusion and Oxidation Wear of PCBN Tool when Cutting Six Workpiece Materials Based on Thermodynamics

Cutting temperature always highly reaches over to 1000°C ? when high speed machining with PCBN tools. Diffusion of tool material element may have important influence on tool wear at such high temperature; the diffusion wear and oxidation wear have become the major wear mechanism. In this paper, the rules of diffusion wear and oxidation wear for PCBN cutting tools are proposed and analyzed based on thermodynamics theory. Dissolution concentrations in typical normal workpiece materials of PCBN tool material at different temperature are then calculated. Diffusion reaction rules in high temperature are developed and analyzed using Gibbs free energy criterion. The machining tests were conducted using the PCBN tools at different cutting speeds of 50, 95,100 and 180 m/min, feed of 0.1, 0.2 and depth of cut of 0.1, 0.8, 1, and 1.5 mm respectively on PUMA300LM numerically-controlled lathe. It was found that the theoretical results were uniform with the experimental data; the results will provide useful references for tool material design and selection.

Wear Mechanisms of Ceramic Tools in High-Speed Turning of Superalloy GH2132

An experimental investigation of wear mechanisms in high-speed turning of superalloy GH2132 with Al2O3-based ceramic was conducted under dry cutting condition. The tool wear mechanisms were characterized by observation of tool wear morphology using scanning electron microscopy (SEM) and detection of the element distribution of the worn tool surface utilizing energy dispersive X-ray spectroscopy (EDS). The results of turning experiments indicated that the major wear mechanisms of the ceramic cutting tool were synergistic interaction between abrasive wear and adhesive wear, and meanwhile the micro-chipping was also observed. It is also shown that cutting distance of the Al2O3-TiC ceramic cutting tool at the speed of 420 m/min was higher than that of the speed of 360 m/min and 540 m/min.

Wear behaviour of a Mg alloy subjected to friction stir processing

In the present investigation, wear behaviour of a Mg alloy AE42 was examined under as-cast as well as friction stir processed conditions. Friction stir processing (FSP) was carried out at an optimized set of FSP parameters. Wear tests were performed in a pin-on-disc configuration using Universal Tribometer. The load range was varied from 5 to 20N, whereas sliding velocity from 0.33 to 3m/s. Worn surfaces and wear debris were analyzed using SEM and EDS for the determination of different wear mechanisms. The friction stir processed (FSPed) AE42 alloy demonstrated significant decrease in the wear rate which may be attributed to the microstructural refinement resulting in enhanced hardness and ductility of the FSPed alloy along with higher work hardening capability. At low loads, wear mechanism transformed from oxidation and abrasive wear at low sliding velocity to delamination at high velocity. At intermediate loads, oxidation and abrasion characterized the worn surface at low velocity, whereas delamination and plastic deformation were found to be major wear mechanisms at high velocities. At high loads, the corresponding mechanisms were abrasion, delamination and plastic deformation at low velocity, whereas severe plastic deformation and delamination at high velocities.