Wear Mode Transition Research Articles

Influence of grit particles characteristics on the abrasive wear micro-mechanisms of NbC-Ni and WC-Co hard materials

Knowledge of wear and associated damage mechanism that is prevalent during abrasive wear conditions using NbC-based cermets is lacking. In the current investigation, the abrasive wear response and associated damage mechanisms of cermets due to characteristics effect of grit particles such as size and hardness have been explored. The present study evaluates the abrasive wear response of NbC-12Ni-10Mo2C (NbC-Ni) cermet during two-body abrasive wear, which was experimentally simulated by a pin abrasion tester following the ASTM G132 standard. The WC-Co cemented carbide (WC-15.6Co) with similar hardness was used as a reference material in this study for a comprehensive comparison of materials. The investigated test parameters included different applied loads (4–16 N) and abrasive particle sizes (22–200 μm) for a 30 m sliding distance at 0.15 m/s sliding velocity. Silicon carbide (SiC) and aluminium oxide (Al2O3) were used as abrasive counter bodies. Test results clearly show the particle size effect and the critical abrasive particle size (CPS) for the cermet lies between 82 μm and 125 μm for both abrasives (SiC, Al2O3). It is noticed that the wear rate shows three different trends as the particle size increases, initial increase then a steady state during critical particle size and becomes unpredictable. This effect reflects the transition of wear micro-mechanisms dominated from binder removal (below CPS) to fracture and fragmentations (beyond CPS). The wear mode transition map from plastic grooving to fracture-dominated failure (fragmentation and granular cracks) was created by correlating factors such as the severity of contact and specific wear rate with microscopic observations. The wear produced by SiC abrasives was about an order of magnitude higher (≈18×) than with Al2O3 abrasives. In addition, the material comparison highlight that the abrasive wear rate of NbC-Ni cermet was about 37–86% (SiC) to 66–83% (Al2O3) higher than for the WC-Co cemented carbide, despite both cermets having similar micro-hardness. In addition, the present study illustrates that the abrasion of cermets is not only related to mechanical properties such as hardness and fracture toughness but is inherently related to composite chemical properties such as wettability and interfacial strength. This work provides new insight into the wear response of NbC-Ni cermets and WC-Co cemented carbides regarding different abrasive counterfaces, abrasive particle sizes and transition of abrasive wear mechanisms.

Micro-scale tribological study of a Ni-Cr-Fe-Ti-Al-V high entropy alloy thin film by magnetron co-sputtering of Inconel-718 and Ti-6Al-4V

In this study, we fabricated high entropy alloy (HEA) thin films by RF magnetron co-sputtering of Inconel 718 and Ti-6Al-4V targets. Their coefficient of friction (CoF) and specific wear rate (K0) were investigated to evaluate their potential as a material for MEMS moving parts. By placing different number of Ti-6Al-4V pellets (samples abbreviated as IT2, IT4, IT6) on an Inconel 718 target (abbreviated as IT0), Ni-Cr-Fe-Ti-Al-V HEA thin films with configurational entropy of mixing (∆Sconf) >1.5R were successfully deposited. Electron microscopy and diffraction confirms that IT0 possessed a mixed nanocrysalline/amorphous structure, while the Ti-added IT2, IT4 and IT6 films were amorphous. They also have a significantly reduced root-mean-square roughness. In order to evaluate their micro-scale wear behavior, various tribological studies including indentation, scratch test and scanning wear test were conducted. From IT0 to IT6, film hardness H increases while reduced modulus Er remains similar. Plastic criterion Rw is also reduced, showing that the films IT2, IT4 and IT6 are more prone to elastic deformation. Scratch test also reveals that IT6 can afford the highest normal load before the transition of wear mode occurs. Lastly, a scanning wear test was conducted to evaluate the specific wear rate (K0) of each HEA film. It was found that IT6 had the lowest value of K0 = 2.26 × 10−4 mm3 N−1 m−1, which was also a lot lower than Si-to-Si (K0 = 0.0183 mm3 N−1 m−1) wear in other studies. The excellence of IT6 can be attributed to the fact that alloying of Ti effectively reduced the average interatomic distance in the HEA films, resulting in a densely packed, very elastic microstructure. Therefore, IT6 is expected to have longer service life than silicon if it were made into MEMS moving parts.

Study on the Micro-Abrasion Wear Behavior of PVD Hard Coating under Different SiC Abrasive Particles/Distilled Water Ratios.

Microscale abrasion has been intensively used to study the wear behavior o several hard coatings, enabling the observation of different wear mechanisms. Recently, a study arguing whether the surface texture of the ball could influence the dynamics of abrasive particles throughout the contact was presented. In this work, the influence of the abrasive particles concentration able to change the texture of the ball was studied to understand its influence on the wear modes-rolling or grooving. Thus, tests were carried out using samples with a thin coating of TiN, deposited using the Physical Vapor Deposition (PVD) technique, and AISI 52100 steel balls etched over 60 s to induce a change in their texture and roughness were used. Three abrasive slurries were prepared with black silicon carbide (SiC) particles (average particle size of 4 μm) with different concentrations, 0.25, 0.35, and 0.45 g/cm3. The rotation speed used in the tests was 80 rpm and the normal loads applied in the study were 0.2 N and 0.5 N, and 1 N. After the wear tests, the coated samples and tracks on the surface of the balls were observed by SEM and 3D microscopy to understand the abrasive particle dynamics, evaluating the wear mode transition as well as the function of both applied load and slurry concentration. The tracks in the balls showed particles embedded on their surface. A lower concentration of abrasion was conducted to higher specific wear rate. Moreover, a predominant two-body wear mechanism was induced when the abrasive concentration was increased. There was an increase in the roughness of the scar and the surface of the balls with an increase in the abrasive particles' concentration.

Influence of Frictional Heat on Wear Mode Transition of Current Collecting Material

Influence of Frictional Heat on Wear Mode Transition of Current Collecting Material

On the quantitative analysis of drill edge wear when machining CFRP/Ti6Al4V stacks

Mechanical drilling of composite/metal stacks is a challenging task due to the rapid tool wear leading to poor hole quality and short tool life. To control effectively the wear process of tools, a scientific understanding of phenomena behind the drill wear progression remains a subject of fundamental importance. The present work aims to quantify the mechanisms of the drill edge wear during the machining of CFRP/Ti6Al4V stacks using diamond-coated twist drills. The novelty of this study lies in identifying the phenomenon of the wear mode transition during the stacks machining. A quantitative analysis was conducted to correlate the flank wear extents at different positions of drill edges with the material removal volume at the constant cutting speed and feed rate. The wear rate of each drill edge segment was studied with respect to the material removal volume. A mechanism transition from adhesion to abrasion is identified after drilling a certain number of stack holes, being the cause of the phenomenon that the drill wear rate decreases with increasing the material removal volume. The results discussed in this paper offer several implications for the structure design and edge reinforcement of drill bits specialized for the machining of CFRP/Ti6Al4V stacks.

Tribological Performance of Al Alloys Dispersed with Carbon Nanotubes or Ni-Coated Carbon Nanotubes Produced by Mechanical Milling and Extrusion

The microstructure, mechanical and tribological behaviors of Al alloy (AA), Al alloy-carbon nanotubes (AC) and Al alloy-Ni-coated carbon nanotubes composites (ANC) fabricated by mechanical milling of elemental powders and subsequent hot extrusion were investigated. Dry sliding wear tests conducted at three different normal loads reveal that the wear rate increases monotonously with the load. The formation and subsequent delamination of the mechanically mixed layer indicate that the general wear mechanism is a combination of sliding and adhesion, while ripple-like worn surface features correspond to wear mode transition. The higher wear resistance exhibited by AC and ANC samples correlates well with the corresponding mechanical properties achieved through the dispersion of carbon nanotubes (CNT) and Ni-coated CNT, following the traditional Archard’s wear relationship.

Improvement in Surface Properties of M50NiL Steel by Plasma Nitriding with Rare Earth Addition

The quenched M50NiL steel was plasma nitrided at 560 °C with and without rare earth (RE) addition. The effect of pure RE lanthanum (La) on the surface properties of plasma nitrided M50NiL steel was investigated using pin-on-disk tribometer. The treated surfaces were characterized using SEM equipped with EDS, XRD and microhardness tester. The results show that the presence of La obviously changes the surface morphologies and phase structures of the nitrided layers. The Fe4N phase appeared on the plasma nitrided surface is replaced by the LaFeO3 phase after introducing La into nitriding atmosphere. A suitable amount of La addition could accelerate the nitriding process by regulating the nitrogen concentration on the nitrided surface. The wear rates of plasma nitrided specimens are apparently lower than that of untreated one. The involvement of La could further reduce the wear rates of plasma nitrided specimens. The specimen plasma nitrided with La addition of 2.5 g demonstrates the best wear resistance with the wear rate of 3.01 ± 0.4 × 10−5 mm3/Nm. The transition of wear mode between adhesion and abrasion is mainly due to the differences in the phase structures and their proportion in the nitrided layers.

High-Temperature Tribology of AA5052/ZrB2 PAMCs

AA5052/ZrB2 particulate aluminum matrix composites (PAMCs) have been produced by in situ reaction of K2ZrF6 and KBF4 compounds with molten alloy at about 860 °C. Dry sliding wear and friction of composites have been investigated for a particular sliding velocity and sliding distance at different loads from ambient temperature to 200 °C. It is revealed that for a particular load and temperature, wear rate and normalized wear rate decrease with increase in the volume percentage of ZrB2 particles whereas coefficient of friction (COF) shows a reverse trend. Wear rate and COF also increase with increase in temperature for a constant load and composition. Whereas with load for a particular temperature, wear rate and wear rate per unit vol. % ZrB2 increase while COF decreases. Worn surface and wear debris morphology examined under scanning electron microscopy (SEM) and profilometer to understand the wear mechanism revealed that wear mode transition takes place from mild-oxidative to severe-metallic at 100 °C for unreinforced alloy, whereas a shifting is observed in transition temperature from 100 to 150 °C for composite with 9 vol. % ZrB2 particles. Energy dispersive spectroscopy (EDS) analysis of worn surface confirms the oxidative wear mode. Profilometry results indicate that wear surface has higher surface roughness at higher values of load and temperatures. Prior to wear and friction studies, composites were also characterized by X-ray diffraction (XRD) and SEM for morphology and microstructural characteristics to correlate with wear results. The findings are very helpful to make the AA5052/ZrB2 composites suitable for the applications, where high-temperature wear is a limiting factor.

An Investigation of the Thermal Sprayed Molybdenum Coatings Behaviour to Micro-Abrasion Wear

The wear behaviour of thick molybdenum coatings deposited by electric arc thermal spray on steel support was investigated by micro-abrasion, a relatively recent introduced method for small scale wear testing. The wear mechanisms and wear rates without coatings penetration were investigated with respect of time corresponding to primary and secondary wear stages. The micro-abrasion of Mo coatings using SiC abrasive slurry have been discussed and wear scar characteristics were evaluated based on the experimentally results. The worn surfaces of the tested specimen were examined by SEM and the specific wear rate was calculated from experimental data. For the testing durations used it was identified the change from grooving to rolling wear corresponding to the transition of wear mode from two-body to three body-abrasion.

The influence of initial roughness and circular axial run-out on friction and wear behavior of Si3N4–Al2O3 sliding in water

Recently, it has been shown that water-lubricated sliding of Si3N4 against Al2O3 can result in steady-state friction coefficient values as low as 0.004. However, most experiments were performed using extremely polished surfaces and did not consider the effect of circular axial run-out of the discs, which could be important in practical applications. In this paper it was investigated the influence of these parameters on the ultra-low friction coefficient (ULFC) phenomenon, including correlations with running-in. Greater initial surface roughness and circular axial run-out resulted in greater running-in duration and wear. In addition, the transition of wear mode from mechanical to tribochemical dominated as a function of sliding distance was clarified and it was proposed that a mixed lubrication regime is required for ULFC to occur.

Modelling of ploughing-cutting transition regime during abrasive manufacturing process

Abrasive manufacturing process is widely used in the automotive manufactures (polishing of valves, crankshafts, camshafts, etc.). To understand the abrasive wear mechanisms during abrasive manufacturing process, a multi-asperity abrasive wear model is proposed. The latter combines different deformation modes of the surface with abrasive wear mechanisms, which depend on a degree of penetration DP (ratio between the groove depth and the half-width of the groove produced by each abrasive grain). This study showed that the wear volume per unit sliding distance increases with the total normal load. At low load, the wear volume increases slowly and the main wear mechanism is ploughing without resulting in material removal. At higher normal load, the wear rate increases with increasing the degree of penetration, leading to the transition in dominant wear mode from ploughing to wedging and cutting.

Influence of particle size and temperature on the wear properties of rutile-reinforced aluminium metal matrix composite

In the present investigations, LM13 aluminium alloy reinforced with 15 and 20wt.% rutile mineral of fine (50–75 µm) and coarse (106–125 µm) size range was prepared through stir casting technique. The microhardness on different phase of the composite was measured to check the interfacial bonding of particles with the base material. The wear properties of the samples were studied using pin-on-disc tribometer at high load (49 N) with variation in temperatures from 50℃ to 300℃. Wear results indicated that the composites containing fine size reinforced particles showed around two times higher wear resistance over a wide range of temperature than the composite-containing coarse particles. A transition in wear mode from mild to severe was observed above 200℃. Wear track and wear debris were analysed to understand the nature of wear.

High-speed wear testing of selected ceramics in abrasive slurry

Due to increased production speeds in modern process environments, the loading conditions in sliding contact applications have become more challenging. Therefore it is important to have good understanding of wear mechanisms in high-speed sliding conditions.A wear testing device was manufactured for the purpose of cost-efficient simulation of water-containing high-speed sliding conditions. Sliding speeds up to 40 meters per second can be achieved while abrasive-containing slurry is fed into the contact interface of material samples and a rubber coated drum. High-speed wear tests were run with three ceramic materials: silicon nitride, silicon carbide and partially stabilized zirconia. Wear behavior of these ceramics was analyzed as a function of sliding speed and slurry composition.Results indicate that in mild wear region increase in sliding speed reduced overall wear, whereas in severe wear conditions increasing speed accelerated wear. A transition from mild to severe wear was observed for silicon carbide when tested in alumina-containing slurry. For the materials that had high enough hardness, wear rates were dictated by the respective order of fracture toughness. Visual inspection of the worn samples supported the interpretation of wear mode transition.

Effect of Particle Size on Wear of Particulate Reinforced Aluminum Alloy Composites at Elevated Temperatures

The present paper describes the effect of particle size on operative wear mechanism in particle reinforced aluminum alloy composites at elevated temperatures. Two composites containing zircon sand particles of 20-32 μm and 106-125 μm were fabricated by stir casting process. The dry sliding wear tests of the developed composites were performed at low and high loads with variation in temperatures from 50 to 300 °C. The transition in wear mode from mild-to-severe was observed with variation in temperature and load. The wear at 200 °C presented entirely different wear behavior from the one at 250 °C. The wear rate of fine size reinforced composite at 200 °C at higher load was substantially lower than that of coarse size reinforced composite. Examination of wear tracks and debris revealed that delamination occurs after run in wear mode followed by formation of smaller size wear debris, transfer of materials from the counter surfaces and mixing of these materials on the contact surfaces. The volume loss was observed to increase with increase in load and temperature. Composite containing bigger size particles exhibit higher loss under similar conditions.

Understanding the friction and wear mechanisms of bulk metallic glass under contact sliding

This paper investigates the friction and wear properties of bulk metallic glass Ti40Zr25Ni3Cu12Be20 (at%) sliding against EN26 steel in a dry environment. It was found that frictional heating plays a central role in the variation of the tribological properties of the material. When the temperature rise does not cause phase transformation but introduces plasticity, the friction coefficient decreases and the wear rate increases. A further temperature rise brings about a wear mode transition from brittle to ductile wear. When the temperature is above the glass transition temperature of the material, crystal particles emerge in the deformed subsurface, and turns the wear to a brittle mode again, even though superplastic deformation of the material also takes place in conjunction with such phase transformation. As a result, friction coefficient increases and wear rate decreases.

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.

Effect of pressure on abrasive wear mode transitions in micro-abrasive wear tests of WC-Co P20

The purpose of this work was to analyse the effect of the pressure (variable and constant) on the wear mode transition in ball-cratering wear tests. It was conducted using balls of 52100 steel, specimens of WC-Co P20 and abrasive slurry prepared with SiC particles and distilled water. The results showed that the conditions of variable and constant pressure had significant effects on the occurrence of the abrasive wear modes and their transitions. Under the condition of variable pressure, the transition from grooving to rolling abrasion occurred earlier than for constant pressure and the ratio Ag/Ap was larger for the condition of constant pressure; Ap is the projected area of the crater, and Ag is the projected area with grooving abrasion.

Experimental study on microscopic wear mechanism of copper/carbon/rice bran ceramics composites

This paper reports on the analysis of microscopic wear mechanisms of copper/carbon/rice bran ceramics (Cu/C/RBC) composites, which were developed as a new pantograph contact strip material for the current collector of electric trains, and the proposal of the wear equation of those composites.Low friction coefficients, of less than 0.15, and relatively low specific wear rates, of less than 10−4mm2/N, were obtained for the Cu/C/RBC composites, when both the mean diameter and the mass fraction of the rice bran ceramics (RBC) particulate were small. At the opposite compounding ratios, the contrary results were obtained. According to SEM observation on wear particles and worn surfaces at low and high wear conditions, different wear modes were observed as follows: ploughing with no typical wear particle; small cracks and small plastic flow with fine wear particles; large brittle fracture and severe plastic flow with flake-like-shaped wear particles.On the basis of the wear mode map of ceramics proposed by Hokkirigawa, the wear mode transition of the Cu/C/RBC composites is discussed. The wear equation which showed the exponential relationship between the specific wear rates and the parameter Sw is proposed. As indicated by this equation, the Cu/C/RBC composites have low Sw values due to their high fracture toughness and low friction coefficient resulting in low specific wear rates.

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.

Improvement of wear resistance for carbon steel under unlubricated sliding and variable loading conditions

Pin-on-disk unlubricated wear tests for 0.35% C steel were conducted in moist air under stepwise loading between low and high levels. The effects of rubbing history under mild or severe wear in the first stage on the transition of wear mode in the second stage were investigated. Under increased loading, in the first stage a highly wear resistant surface is formed by oxidation, work-hardening and flattening of contact surfaces for a long sliding distance under mild wear. In the second stage, the worn surface can bear high loads at which severe wear occurs under constant loading. This brings about a low specific wear rate under quasi-mild wear, which has been newly defined by the authors. The upper critical load (PAcr,i) under increased loading between severe and quasi-mild wear is quite higher than that (PAcr,c) under constant loading, leading to a considerable improvement in wear resistance. Under decreased loading, severe wear for very short sliding distance in the first stage generates unoxidized, roughened worn-surfaces with a highly deformed, hardened layer. In the second stage the worn surface is slightly oxidized at a low load for a long sliding distance, resulting in quasi-mild wear. However the critical load (PAcr,d) under decreased loading is slightly higher than the critical load (PAcr,c) under constant loading, meaning little improvement in wear resistance.