Fundamental Wear Mechanisms Research Articles

A predictive wear model in grinding using single-layer electroplated cBN tools

Wheel wear is a complex phenomenon significantly affecting grinding performance. While microscopic grit observation can detect various wear mechanisms, a predictive model is required to anticipate the total wear behavior under diverse grinding conditions. This study incorporates all wear mechanisms, including pullout, attrition, and fracture, into an analytical model aimed at determining improved grinding conditions. The grinding particles are approximated as standard constitutive geometries to model the wheel surface topography and the grit height reduction obtained from the wheel surface roughness is correlated with wear. The present model introduces an innovative approach to tracking and predicting wheel wear performance, eliminating the need for time-consuming grit micro-observation. Numerous grinding tests employing different tools were conducted, revealing strong agreement between the experimental results and the model predictions. The Application of this approach for predicting prolonged tool life is also demonstrated. Finally, the paper discusses how these findings contribute to a deeper understanding of the fundamental wear mechanisms in the grinding process.

Wear behavior of different coated tools in MQL-assisted milling of magnesium-based rare-earth alloys

One of the most important and often employed indicators for describing machinability and machining quality is tool wear. While flank wear is commonly used to gauge the extent of a worn scar, tool wear is characterized more by its shape than its size. To quantify the wear shape, more specific data concerning the wear contour is required. With this aim, the present work addresses the fundamental wear mechanisms and failure modes of several coated tools used in the mechanical milling of rare-earth magnesium (Mg-RE) alloys. Uncoated, edge-strengthened, TiAlN-coated, and diamond-coated tools were tested under dry and minimal quantity lubrication (MQL) conditions. The cutting energy flow and consumption rules governing the tool wear processes were quantified using the exergy analysis theory. The results indicate that the cutting performances of tools and the surface quality are both enhanced by the MQL through reducing adhesion wear. For the unstrengthened tool, a tool wear reduction of 55% is achieved by the MQL. While for the TiAlN-coated tool, the tool wear can be furtherly suppressed by 49%.

Tribological behaviors of nanotwinned Al alloys

Wear-induced damages cause significant materials loss each year. Al alloys are widely used by industry but usually have low wear resistance. Here, we compare the tribological behaviors of ultrafine grained Al, a nanoprecipitate hardened Al 7075 alloy and nanotwinned Al–Ni alloys using the nanoscratch. The nanotwinned Al–Ni alloys exhibit lower coefficient of friction and much greater wear resistance than the Al and Al 7075 alloys. The enhanced wear properties of Al–Ni alloys arise from their high strength and the evolution of nanotwinned microstructures into gradient nanograins during wear. These findings on fundamental wear mechanisms in nanotwinned alloys may advance the discovery of wear-resistant metallic materials.

Graphite lubrication mechanisms under high mechanical load

In this study, the fundamental wear mechanisms of graphite were studied in sliding friction under high mechanical load. For these investigations, graphite coatings of various thickness were applied with an airbrush spray gun onto substrates with two roughness levels. When tested in a microtribometer, as film thickness was increased from 0.2 to 17 μm, the coefficient of friction increased 3.6-fold, due to higher ploughing effects; the higher thickness, however, resulted in an extended lifetime of the coating and a lower counterbody wear. As the pressure was elevated up to 1 GPa a decrease in friction was observed with a coefficient of friction as low as 0.12. The performance could be additionally improved in terms of friction, wear, and lifetime by increasing the substrate roughness by a factor of seven. An increased lifetime up to 7.6-fold was achieved due to the formation of a stable, 30–150 nm thick carbon layer in the tribocontact. During all experiments graphite is transferred onto the counterbody and transported out of the wear track during the first ten friction cycles. The observed carbon layer consists of compressed graphite material in the friction track that was transported from the sides, thus filling and covering the trenches of the rough substrate and thereby reducing contact pressure.

On the machining behavior of carbon fiber reinforced polyimide and PEEK thermoplastic composites

AbstractPolyimide (PI) and polyetheretherketone (PEEK) are superior high‐performance thermoplastics being extensively used in the fields of fiber‐reinforced polymer composites. However, there is very limited literature addressing the machining behavior of the PI and PEEK composites. The present paper aims to conduct a comparative study into the machining characteristics of these two representative high‐performance thermoplastic matrix composites under varying cutting conditions. Machinability aspects of the carbon/PI and carbon/PEEK thermoplastic composites were evaluated in terms of drilling forces, machining temperatures, delamination damage, surface morphologies, hole dimensional accuracy and tool wear. The results indicate that the carbon/PEEK composites generally show a much poorer machinability than the carbon/PI composites in terms of higher drilling forces, higher cutting temperatures, larger delamination extents and excessive tool wear. Since the carbon/PEEK composites exhibit certain ductility leading to the continuous chip formation, the cut hole surface morphologies and dimensional accuracy are much better than those gained in the carbon/PI composites. Both the cutting speed and the feed rate affect significantly the drilling forces and the resulting delamination damage. The fundamental wear mechanisms of drilling carbon/PI composites are abrasion wear in the form of edge rounding and slight chip adhesion, while for the carbon/PEEK composites, they are abrasion, serious chip adhesion because of the high drilling temperatures promoted at the drill‐work interface and catastrophic failures of coating peeling and edge fracture.

The fundamental mechanisms of wear of cemented carbide in continuous cutting of medical grade cobalt chromium alloy (ASTM F75)

Medical grade cobalt chromium alloys are one of a select number of material types approved for use in the components of orthopaedic implants. However, there has been minimal published research into the fundamental mechanisms in the cutting processes used in their manufacture. These processes affect the form accuracy, surface finish and integrity of these safety critical devices.The present work reports on a scientific investigation into the fundamental mechanisms of tool wear in continuous cutting of the biomedical grade Co-Cr-Mo ASTM F75 alloy using uncoated tungsten carbide tools. Confocal and scanning electron microscopy (SEM) is used to examine and characterise the progression of tool wear at intervals up to a defined “end of life limit” for each combination of speed (vc) and feed rate (f) in experiments where the range of these parameters vary from 20 to 60 m/min and 20–60 μm/rev respectively to reflect the ranges used in industry.An empirical model is then established for progressive tool wear which demonstrates that the wear rates vary by over an order of magnitude. The parameters for the Taylor equation are also determined for this material for the first time. Microscopic examination shows the presence of characteristic tool wear “zones” with consistent size, shape and composition. These zones evolve depending on combination of speeds and feeds as determined in the full factorial experiment. Detailed characterisation of the wear surfaces and cross sections provide a number of insights into the possible mechanisms of wear. It is hypothesised that micron thick layers of Co-Cr-Mo, found on the rake and flank wear surfaces, indicate primary wear mechanism involving adhesion of the work material and subsequent removal of WC hard particles by entrainment in the work material flow.

Temperature and load influence on in-situ formed layers during high temperature abrasion

Abrasive wear at high temperature (HT) applications is a serious issue in industry, limiting the lifetime of core components, e.g. in steel- or cement production. In literature abrasive wear is commonly linked to material's hardness, but it is known that microstructure and temperature show also major influence. Current studies also found wear protecting effects by the in-situ formation of mechanically mixed layers (MML) with the abrasive, which can be especially beneficial at HT.To investigate the temperature and load influence of this MML formation at high-stress abrasive conditions a modified ASTM G65 test, allowing for temperatures up to 700°C, was utilised. Two metal matrix composite (MMC) materials prone to MML formation were chosen: a Ni-based and Fe-based cast alloy with carbide content of ~15%. Thereby the MMC matrix influence on MML formation was studied. Load was varied from 10 to 45 and 80N, and temperature from room temperature to 500°C and 700°C. Abrasive is collected during tests in order to determine the severity of the contact during the wear process. Post-test analysis investigate the MML coverage and depth in order to estimate the wear protecting effect. Further micro-hardness investigations and nano-scratch experiments identified fundamental wear mechanisms and load bearing capacity of the hard phase network.It was found that increasing load leads to higher severity of the contact (more abrasive breakage). MML coverage was strongly dependent on load and temperature at the Fe-based material. Despite a pronounced drop of the hardness at 500°C this material features efficient wear protection by MML formation at HT. On the other hand the Ni-based MMC shows minor temperature and load influence on MML formation, which can be put down to its relative temperature stable fcc matrix. Wear rates of the Ni-based MMC are superior to the Fe-based material at highest testing temperature. Strain hardening and dynamic recrystallisation were found to be beneficial especially at 500°C for the Ni-based MMC.

An approach to understanding tribological behaviour of dental composites through volumetric wear loss and wear mechanism determination; beyond material ranking

ObjectiveTo investigate the fundamental wear mechanisms of six resin-based composite (RBC) formulations during short-term in vitro wear testing. MaterialsRBC materials were condensed into rectangular bar-shaped specimens and light irradiated using the ISO 4049 specimen manufacture and irradiation protocol. Wear testing (n=10 specimens for each RBC) was performed on a modified pin-on-plate wear test apparatus and wear facets were analysed for wear volume loss using a white light profilometer. The wear tested RBC specimens and their corresponding antagonists were analysed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively to determine the wear mechanism. ResultsData generated using the profilometer showed variations in the mean total wear volume (mm3) between the RBCs tested (p<0.05). Abrasive wear was evident in all RBCs investigated with varying degrees of damage. Material transfer/deposition of the filler particles on the corresponding antagonists was evident in two RBC materials (Filtek Supreme and Kalore) indicative of a further adhesive wear mechanism. ConclusionIt is proposed that the approach employed to use a combination of measurement and analytical techniques to quantify the wear facet volume (profilometry), wear trough (SEM) and material transfer (EDS) provides more useful information on the wear mechanism and the tribology of the system rather than relying on a simple wear ranking for the RBC materials as is routinely the case in dental research studies.

トライボロジー（摩擦・摩耗・潤滑の学問）の基礎から応用，最近の進歩

To extend the wear lives of tribomaterials, the proper control of wear rate is desired. The description of wear rates is shown at the first portion. The fundamental wear mechanisms for rubbers and polymeric materials, such as abrasive wear and adhesive wear, are explained in this paper.

Investigation of fundamental wear mechanisms at the piston ring and cylinder wall interface in internal combustion engines

This research examined the cylinder liner-piston ring system simultaneously from the metallurgical and metrological standpoints, using specimens cut from real engine components (rings and liners), in order to identify the mild and severe wear mechanisms. Work has been conducted using a Plint TE77 high frequency friction machine. Metrological analysis was performed using stylus contacting profilometer. Metallurgical analysis of the samples was carried out using a JOEL JSM-6400 scanning electron microscope. In addition to wear, the coefficient of friction (μ) was recorded for every piston ring - cylinder liner pair so as to observe the transitions between mixed and boundary lubrication. This paper presents the results obtained using flame sprayed Mo-coated spheroidal graphite cast iron, which is an old piston ring coating and is not available anymore, and relatively new Federal Mogul CKS-36™ top compression rings tested against a grey cast iron cylinder liner tested at two different bulk oil temperatures (90 °C and 140 °C), two different pressures (3.9 MPa and 6.5 MPa) and with two different lubricants (SAE 0W20 with a Friction Modifier and SAE 15W40).

Tribological and Nanomechanical Properties of Unmodified and Crosslinked Ultra-High Molecular Weight Polyethylene for Total Joint Replacements

Wear of ultra-high molecular weight polyethylene (UHMWPE) continues to be a major obstacle limiting the longevity of total joint replacements. Efforts to solve the wear problem in UHMWPE have resulted in numerous studies dealing with the microstructure, morphology, and mechanical properties of this polymer. However, the fundamental wear mechanisms at different material length scales in total joint replacements remain elusive. Consequently, a systematic investigation of the initial stage of the wear process was performed in this study in order to obtain insight into the origins of wear in UHMWPE at submicrometer scales. Sliding experiments were performed with both unmodified and crosslinked (by gamma radiation treatment) UHMWPE subjected to reciprocating sliding against Co-Cr alloy in a bath of bovine serum under ranges of mean contact pressure and sliding speed typical of knee joints. Nanoindentation and optical, scanning electron, and transmission electron microscopy were used to examine the effect of crosslinking on the nanomechanical properties, dominant wear mechanisms, and microstructure of UHMWPE. The fundamental wear micromechanisms of unmodified and crosslinked UHMWPE are interpreted in the context of coefficient of friction, wear factor, creep, adhesion force, and microstructure results.

Tribological evaluation of oil pump relief valve coatings compatible with an aluminum oil pump body

Wear can cause automotive relief valves to jam. In order to evaluate and screen candidate coatings for oil pump relief valves for reduction of aluminum pump cylinder bore wear and wear-related sticking, a laboratory reciprocating wear test using production parts has been developed. The coatings on valves include impinged and physical vapor deposited (PVD)-coated molybdenum disulfides, electroplated nickel–phosphorous with polytetrafluoroethylene (Ni–PTFE), electroplated bronze, and electroplated nickel–phosphorous–boron nitride (Ni–P–BN).The test results showed that the electroplated bronze coating demonstrated the best wear resistance against 380 aluminum pump bores while Ni–PTFE ranked second, PVD-coated MoS2 third, and Ni–P–BN ranked last. It was observed that the electroplated bronze coating showed only mild oxidative or abrasive wear after 20h wear test. The Ni–P–BN coating gave the worst wear resistance due to severe abrasive wear, surface scoring, and coating abrasion during the wear test. The major wear mechanisms for valve bore/relief valve can be classified at different levels from mild wear (oxidative wear or surface delamination) to abrasive wear (scoring, scuffing, and ploughing). This paper also reviewed the rooted wear mechanisms of production pump relief valves against aluminum bores based on metallographic observations of worn surfaces after field tests. This tribological investigation of valve coatings has provided insights into the fundamental wear mechanisms which depend on the compatibility of two sliding materials, protective coating composition, hard particle content, and surface interaction. The information will be useful in preventing oil pump relief valves from jamming.

Wear in relation to friction — a review

Soft or hard film coating, multi-phase alloying and composite structuring have been developed to control wear and friction by improving materials and surfaces with some aspects for better properties of friction and wear. On the other hand, it is well recognized recently that the coefficients of friction and wear are not material properties but two kinds of responses of a tribo-system. They are always reasonably related with each other when the necessary functions of the tribo-system are well considered. Typical wear behaviors of representative materials of coatings, composites, metallic alloys and ceramics are reviewed in relation to their friction behaviors, and fundamental mechanisms of wear are confirmed for the technical development of wear control.

Frequency dependence of the lifetime of a surface micromachined microengine driving a load

Abstract Experiments have been performed on surface micromachined microengines driving load gears to determine the rotational frequency dependence on median cycles to failure. A sample of 272 microengines, each driving a load, was stressed at eight different frequencies. Frequency dependence was observed and a model was developed based on fundamental wear mechanisms and forces exhibited in resonant mechanical systems. Stressing loaded microengines caused observable wear in the rotating joints and in a few instances led to fracture of the pin joint in the drive gear.

Current Concepts Review - Wear in Total Hip and Knee Replacements*

Before the advent of total joint replacement, patients who had end-stage arthritis of the lower extremities had unremitting pain and a greatly decreased functional capacity. In addition, they often were confined to a wheelchair and were dependent on the care of others. Today, the outcomes of primary total hip and knee replacement are predictable and usually excellent35,45,57,64,212,221. Prosthetic joint replacement has dramatically improved the lives of millions of people worldwide. As the fixation of total joint implants has become more reliable and durable and as the technology of total joint replacement has been applied to younger and more active patients, the current limitations of total joint arthroplasty are related to the wear of the components248. Wear is the removal of material, with the generation of wear particles, that occurs as a result of the relative motion between two opposing surfaces under load. In complex mechanical-biological systems such as total hip and knee replacements, there can be many types of wear. Although the mechanical consequences of wear, such as progressive thinning of polyethylene components, can limit the functional life of a joint replacement, the clinical problems from wear more frequently are due to the release of an excessive number of wear particles into a biological environment. When particles within a certain size-range are phagocytized in sufficient amounts, the macrophages enter into an activated state of metabolism, releasing substances that can result in periprosthetic bone resorption. Progressive loss of periprosthetic bone can necessitate a reoperation, which is the definitive measure of clinical failure of a joint arthroplasty. It is important to distinguish among the fundamental mechanisms of wear (adhesion, abrasion, and fatigue); the changes in the appearance (the morphological characteristics) of the bearing surfaces, which are referred to …

Tribological properties of metal matrix composites

High wear resistance is an attribute frequently ascribed to metal matrix composites and is of clear importance to the designer is considering both the use of these materials in some applications and in selecting the machining processes which can be employed to fabricate components. Sliding wear of metal matrix composites is important wherever there is relative motion, either deliberate or unintentional. If hard particles are present in the system, for example, as contamination in a lubricant or intentionally in abrasive machining, then the abrasion resistance of the material may be relevant. This critical review considers the complex tribological behaviour of metal matrix composites with fibre, whisker, and particulate reinforcement. Under certain conditions, metal matrix composites show high wear resistance, but this is not always the case; an understanding of the fundamental mechanisms of wear is essential in order to use them more efficiently.MST/2057