Ultra-low Wear Rates Research Articles

Achieving ultra-low coefficient of friction of FeCoNiW multi-bonded composite coatings by Co-coated WC

It is of paramount importance to enhance the surface wear resistance and reduce the impact of corrosion caused by the marine environment in order to guarantee the propeller transmission components’ exterior protection. FeCoNiW multi-bonded Co-WC composite coatings were prepared with an ultralow friction coefficient (0.17) and wear rate (7.22 ×10−7 mm3⋅N−1⋅m−1) in this research. The uniform and fine hard phase skeleton, which is cobalt-rich, ensures that the coating exhibits reliable tribological characteristics. Furthermore, this coating exhibits high hardness (1000HV0.3 at 80 wt.%Co-WC) and sufficient low current density (7.485 ×10−6 A/cm2). The primary reason for these enhanced attributes is a reduction in the density of flaws in the coatings. Consequently, Co-WC-added composite coatings have considerable potential for utilization in drive shaft components and propeller applications.

Macroscale structural superlubricity: Dynamic evolution of tribolayers in two-dimensional materials under extreme pressure

Achieving macroscale structural superlubricity with two-dimensional (2D) materials under ultrahigh contact pressure in ambient condition is particularly challenging. Furthermore, the mechanisms underlying the disparate trans-scale tribological behaviors of 2D materials continue to be a subject of debate. Here, we propose a novel principle concerning pressure-induced dynamic structural evolution and tribochemical behaviors of tribolayers to broaden the macroscale structural superlubricity. For the first time, robust macroscale structural superlubricity with ultralow wear rate is realized by 2D material coating in ambient condition by sliding steel counterparts under ultrahigh contact pressure. The results reveal that macroscale structural superlubricity of 2D materials is highly dependent on the dynamic evolution of tribolayers nanostructures, as well as the adsorption and tribochemical behaviors governed by extreme pressure. These findings shed light on achieving robust macroscale structural superlubricity with 2D materials for harsh engineering conditions.

Achieving the ultra-low friction and wear rate of PEEK-PTFE composites by Ti3C2Tx MXene reinforcement

In this work, a series of poly(ether-ether-ketone) (PEEK) and poly(tetra-fluoroethylene) (PTFE) composites reinforced by Ti3C2Tx MXene are fabricated, and the mechanical as well as tribological properties are investigated. The MXene forms a strong bonding with both PEEK and PTFE, thus improving the compressive strength by 28.37 % when compared to the undoped composite. Meanwhile, the MXene selectively adheres PTFE on the ZrO2 counterpart and facilitates the formation of transfer tribofilm. Eventually, the PEEK(Ti3C2Tx)-PTFE composites reach an ultra-low coefficient of friction (COF) of 0.065 ± 0.003 accompanied by a decrement in wear rate of 40 %. The promising performances of PEEK-PTFE composites by MXene reinforcement indicate an efficient way towards self-lubricating composites.

Wear of alumina-PTFE against brass and aluminum: Role of interfacial films and tribochemistry

PTFE matrix composites reinforced with α-Al2O3 fillers are considered a gold standard polymeric solid lubricant. α-Al2O3 PTFE exhibits ultra-low wear rates (k ∼10−8 mm3/Nm) when sliding against steel in the presence of water vapor. Mechanochemical interactions involving the breaking of PTFE chains, and subsequent oxidation in the presence of water vapor helps promote growth of interfacial films that are strongly bound to the sliding interface. In the absence of moisture, wear rates of α-Al2O3 PTFE can increase by as much as three orders of magnitude, underscoring its importance to ultra-low wear behavior. A similar increase in wear rates of α-Al2O3 PTFE in humid environments has recently been observed when sliding against brass counter surfaces, though reasons for this increase remain unclear. These findings suggest that mechanisms of ultra-low wear not only rely on ambient humidity but are also strongly dependent on the counter surface chemistry. In the present work, we test the hypothesis that counter surface chemistry drives alumina PTFE wear by systematically investigating the wear of an α-Al2O3 PTFE composite against brass and aluminum substrates within the context of the morphological and mechanochemical evolution of the sliding interface. Wear tests are conducted under reciprocating, dry sliding conditions. Results presented in this work offer insights on mechanochemical mechanisms that drive wear of α-Al2O3 PTFE against brass and aluminum, and provide a framework for developing strategies for controlling wear.

An Ultrahigh Power Density and Ultralow Wear GaN-Based Tribovoltaic Nanogenerator for Sliding Ball Bearing as Self-Powered Wireless Sensor Node.

The tribovoltaic effect is regarded as a newly discovered semiconductor effect for mechanical-to-electrical energy conversion. However, tribovoltaic nanogenerators (TVNGs) are widely limited by low output power and poor wear resistance for device integration and application. Here, this work invents a TVNG using a ball-on-disk structure composed of gallium nitride (GaN) and steel ball. It exhibits an open-circuit voltage exceeding 130V and an ultrahigh normalized average power density of 24.6kW m-2 Hz-1 , which is a 282-fold improvement compared to previous works. Meanwhile, this TVNG reaches an ultralow wear rate of 5×10-7 mm3 N-1 m-1 at a maximum contact pressure of 906.6MPa, surpassing the TVNG composed of Si by three orders of magnitude due to the local concentrated injection of frictional energy. Based on the TVNG, this work constructs the first tribovoltaic bearing and achieves sensing signal transmission within 16 s (300 rpm) by integrating a management circuit, a transmission module, a relay, and receiving terminals, which enables the monitoring of ambient pressure and temperature. This work realizes a GaN-based TVNG with high-performance and low wear simultaneously, demonstrating great potential for intelligent components and self-powered sensor nodes in the industrial Internet of Things.

WS2-Ti-based solid-liquid synergetic lubricating coating with super-high wear resistance for space application

Solid-liquid lubricating technology is a quite effective approach to achieve long life for sliding components in space. Herein, the WS2-Ti films with porous and dense structures were prepared. The tribological performances of WS2-Ti films lubricated in two kinds of space liquid lubricants (P201 and PFPE) were mainly investigated in vacuum compared to the films in dry friction condition. The dense film exhibits the low friction coefficient of 0.02 and ultra-low wear rate of 2.3 × 10−8 mm3·N−1·m−1 in the dry friction condition. The dense film/oil coatings also show a very long wear life over 4.5 × 105 r, and their wear rates obviously decrease about 79 % and 67 % under harsh test condition compared to the porous film lubricated in P201 and PFPE, respectively. The related analyses indicate that nonpolar P201 molecule is found to have far better compatibility to WS2-Ti crystal surfaces than polar PFPE molecule. It contributes to forming compact tribolayer consisting of numerous ultrathin nanosheets, significantly extending wear life of the coating. Noteworthily, for the solid-liquid coatings, there is a new find that formation of transfer film firstly underwent amorphization and then occurred recrystallization. This reveals lubricating mechanism of the WS2-Ti/oil coating.

Insights of the Ultralow Wear and Low Friction of Carbon Fiber Reinforced PTFE in Inert Trace Moisture Environment

Ultralow wear rates and low friction have been observed for carbon fiber reinforced PTFE (CF/PTFE) when sliding against steel or cast iron in dry gas environments. Although the strong environmental sensitivity of this tribosystem is well known, the origin of the outstanding tribological performance in dry gas remains unanswered. Some researchers attribute the low friction and wear to the formation of carbon-rich surfaces in the absence of oxygen and moisture in the environment. However, low friction between carbon surfaces is generally dependent on moisture. In this paper, extensive analyzes are conducted on the tribofilms formed on the CF/PTFE surface and the steel counterface after sliding in a high-purity nitrogen environment. TEM analysis of a cross-section of the tribofilm on the steel surface reveals that the sliding surface consists mainly of iron (II) fluoride and not carbon, even though a significant amount of carbon was observed near the surface. XPS and TEM analysis further revealed that the tribofilm formed on the worn composite surface consisted of nanoparticle agglomerates, anchored to the PTFE matrix and to each other by carbon with turbostratic structure. Turbostratic carbon also formed an ultrathin and surface-oriented superficial layer on top of the agglomerates. Governing mechanisms of the low friction and wear of the CF/PTFE—steel tribosystem were investigated by complementary tribotests with pure graphite samples and MD simulations of the identified surfaces. These indicated that the low friction between the carbon and iron fluoride in the tribofilms is due to poor adhesion between the distinctly different surfaces.Graphical

Contact pressure dependent mechanisms of ultralow wear PTFE composites

One of the most dramatic reductions in the wear of PTFE has been achieved by compositing PTFE with as little as 1–5 wt% of alumina particles; this has been reported to produce wear rates K ∼10−7 mm3/Nm. The mechanisms associated with this reduction in wear are multifaceted, including 1) preventing crack propagation and delamination of the PTFE wear surface, 2) promoting tribochemistry and more recently 3) tribologically-induced breaking of the filler into nanoscale fragments to stabilize and reinforce tribofilms. However, in an effort to keep experiments comparable, many of the studies throughout the literature have focused on a narrow contact pressure range. In these experiments, we explored the effects of contact pressure on the tribological behavior of different PTFE and alumina composites, one of which is reported to achieve ultra-low wear (∼10−7 mm3/Nm) and another that is reported to only have mild reductions in wear (∼1 × 10−5 mm3/Nm) compared to unfilled PTFE (∼4 × 10−4 mm3/Nm). We found that with decreased contact pressures, the PTFE-alumina composite that was previously reported as high wear could achieve ultralow wear rates. The PTFE-alumina composite previously reported to achieve ultralow wear achieved ultralow wear at a range of low to high contact pressures, with a higher pressure limit corresponding to increases in wear. The friction behavior of PTFE-alumina composites was found to be highly dependent on contact pressure, with increasing pressures resulting in decreasing friction coefficients (∼0.5–0.17 over a 0.62–8.5 MPa range). This effect became more pronounced when the contact pressure was incrementally varied during testing resulting in up to a 70% decrease or increase in friction coefficient due to increasing or decreasing the pressure, respectively. IR spectra of the polymer wear surface showed that tribofilms rich in carboxylates and metal oxides form at the full range of contact pressures tested, even at the extremes. This formation of tribofilms at the sliding interface not only contributes to the ultralow wear of these materials, but plays a role in the friction behavior observed. From this, we gained new insight into the role, functionality and limitations of the alumina fillers.

Effects of deposition temperature on the wear behavior and material properties of plasma enhanced atomic layer deposition (PEALD) titanium vanadium nitride thin films

This work investigates the effects of deposition temperature on the wear behavior and material properties of recently developed plasma enhanced atomic layer deposited (PEALD) TiVN films. ∼50–100 nm thick TixV1-xN (x ~ 0.5, hereto referred to as TiVN) films were deposited using PEALD on Si substrates with thermal oxide at a range of deposition temperatures (150 °C, 200 °C, 250 °C, 300 °C, 350 °C). Wear testing was performed on each film using a linearly reciprocating tribometer in a controlled humidity environment. Wear rates of the TiVN films varied with deposition temperature, with the 250 °C sample achieving ultralow wear(5.4 × 10−7 mm3/Nm), while the 150 °C sample wore through the film completely in early sliding cycles. Along with their low wear properties, these PEALD TiVN films were found to have low electrical resistivity when deposited above 150 °C. Film density and crystallite size increased with increasing deposition temperature up to 250 °C, where these properties plateaued. High compressive residual stresses were measured, ranging from 2.7 to 7.7 GPa. XRD Bragg peak intensities showed that films with increasing deposition temperatures had higher degrees of crystallinity. XPS indicated that above 150 °C deposition temperatures, impurities in the film were reduced by ∼4x. Higher deposition temperatures allow for increased adatom mobility, which can lead to higher densities and crystallinity, which are typically associated with lower wear rates. At deposition temperatures below 200 °C, precursor reactivity is sluggish and there is insufficient energy for complete surface reactions to occur, leading to film contamination and less dense films. The subtle differences in wear rates above 200 °C deposition temperature indicated that there are competing material properties that can either contribute to or detract from the wear behavior of the film, and a combination of desirable mechanical, physical, structural, and chemical properties are required for ultra-low wear rates to be achieved. The low wear and friction properties and low electrical resistivity of these films combined with the low deposition temperature, conformality, and atomic layer thickness control of PEALD make them potential candidates for applications such as thermally sensitive microelectronics and MEMS/NEMS.

Microstructure evolution and deformation mechanism of coherent L12-strengthened high-entropy alloy during sliding wear

Face-centered-cubic high-entropy alloys (HEAs) strengthened with coherent ordered nanoprecipitates have demonstrated excellent strength-ductility synergy, even at elevated temperature. However, there still lacks fundamental understanding on their microstructure evolution and deformation mechanisms during dry sliding wear. Herein, we systematically investigated the friction and wear behaviors of CoCrNi2(Al0.2Nb0.2) alloy with high-density coherent L12 nanoprecipitates during sliding at room and elevated temperatures, with particular focus on wear-induced microstructure evolution. The alloy shows a low wear rate of 1.80 × 10−5 mm3/(N⋅m) at room temperature (RT) and even an ultralow wear rate of the order of 10−6 mm3/(N⋅m) at 600 °C. Detailed TEM analyses reveal that sliding-induced stacking faults (SFs) and dislocation cells play important roles in the formation of the gradient microstructure at RT and 600 °C, respectively. The superior wear resistance at RT is mainly attributed to the precipitation strengthening of high-density coherent L12 phase and the dynamic work-hardening of SF networks near the sliding surface. However, at 600 °C, the reduced wear rates and coefficients of friction are associated with the formation of glaze layer and the high resistance to thermal softening. This work provides significant insight into the sliding-induced microstructure evolution and deformation mechanism of L12-strengthened high-entropy alloys during sliding wear.

High-performance multifunctional (Hf 0.2Nb 0.2Ta 0.2Ti 0.2Zr 0.2)C high-entropy ceramic reinforced with low-loading 3D hybrid graphene–carbon nanotube

There has been growing interest in the high-entropy ceramic (HEC) recently owing to its tailorable compositions and microstructures, versatile properties, together with promising structural and functional applications. However, inferior fracture toughness (<i>K</i>_IC) and damage tolerance restricted many practical applications of the HEC. Herein, we addressed this challenge by incorporating a three-dimensional graphene–carbon nanotube (3D G–CNT) as toughening agent in (Hf_0.2Nb_0.2Ta_0.2Ti_0.2Zr_0.2)C. The resulting enhanced 3D G–CNT/(Hf_0.2Nb_0.2Ta_0.2Ti_0.2Zr_0.2)C featured an outstanding toughness of 8.23 MPa·m^1/2, while remaining superior strength (763 MPa) and hardness (24.7 GPa). An ultralow friction coefficient (0.15) coupled with an ultralow wear rate (<i>w</i>, 2.6×10⁻⁷ mm³/(N·m)) in the 3D G–CNT/(Hf_0.2Nb_0.2Ta_0.2Ti_0.2Zr_0.2)C was obtained primarily as a function of lubricating scrolls, in which two-dimensional (2D) graphene acted as a tribolayer, and one-dimensional (1D) carbon nanotubes acted as nano ball bearings embedded inside. Strikingly, the 3D G–CNT/(Hf_0.2Nb_0.2Ta_0.2Ti_0.2Zr_0.2)C exhibited rather low thermal conductivity (<i>κ</i>) yet excellent electrical conductivity (<i>σ</i>, 1.3×10⁶ S/m) in comparison with the pure (Hf_0.2Nb_0.2Ta_0.2Ti_0.2Zr_0.2)C. This study provided great potential for maximizing the physical and functional properties of the HEC for various applications.

Enabling macroscopic superlubricity in TaC/a-C nanocomposite film by atomic-level Au

Endowing the hard protective coating systems with macroscopic superlubricity can adequately minimize unnecessary material consumption and energy waste caused by friction and wear. Herein, a novel scheme for realizing superlubricity-protective bifunction is demonstrated, namely introducing atomic-level dispersed Au atoms (∼1.4 at.%) into the TaC / amorphous carbon (a-C) nanocomposite structure consisting of the TaC-nanoparticles-based network backbone and the a-C filler. With the aid of the atomic-level dispersed Au atoms reducing the ordered transformation barrier of a-C, the in-situ formation of graphite-like carbon (GLC) flakes during the sliding process wrap the TaC grains to form TaC@GLC nanoscrolls in the shearing layer for multi-contact configuration and incommensurate contact, thereby obtaining the robust macroscopic superlubrication with the friction of coefficient of ∼0.002 and the ultra-low wear rate of ∼8.80 × 10−10 (mm−3/Nm). This strategy of triggering in-situ self-assembled nanoscrolls from hard protective coatings provides a new avenue to enable macroscopic superlubricity for robust engineering applications.

Clarifying the importance of the running film to the ultra-low wear of the polymer composite by eliminating its individual effect

Polytetrafluoroethylene (PTFE) composites with suitable fillers can exhibit ultra-low wear via transfer and running films formation and the prevention of matrix removal. However, they are often generated simultaneously, thereby making it difficult to distinguish their individual effects. In the present study, dual-pin-on-disk (DPOD) friction pairs are used to tailor the combination of different functions, so that the individual effects of the running and transfer films are identified. The results show that the running film formed on the worn polymer surface is indispensable for achieving ultra-low wear. The high-quality transfer film formed on the counterpart steel surface only slightly improves the wear performance individually, whereas ultra-low wear rates are achieved via the synergistic effect of the running and the transfer films.

Remarkable Wear Resistance in a Complex Concentrated Alloy with Nanohierarchical Architecture and Composition Undulation.

Sustained wear damages on the sliding surfaces of alloys are generally the culprit responsible for the failure of various mechanical systems. Inspired by high-entropy effects, here we deliberately deploy nanohierarchical architecture with composition undulation in a Ni50(AlNbTiV)50 complex concentrated alloy, which yields ultralow wear rate within the order of 10-7 to 10-6 mm3/Nm between room temperature and 800 °C. Such remarkable wear resistance heretofore represents one of the highest wear resistance reported for the bulk alloys or composites, and originates from the multi-type adaptive friction interface protection governed by intrinsically nano-coupled grains and nanoprecipitates. This cooperative heterostructure releases gradient frictional stress in stages upon wear at room temperature through the coexistence of multiple deformation pathways while activating a dense nanocrystalline glaze layer upon wear at 800 °C to minimize adhesive and oxidative wear. Our work uncovers a practical avenue for tailoring wear properties with multicomponent heterostructures over a wide temperature range.

Design and Pore Properties Tuning of Two‐Scale Porous Polyimide Fabricated by Isostatic Pressing for Improving Oil Storage and Tribological Properties

The development of smart lubricating materials with lasting lubrication and outstanding wear resistance while achieving speed response is of great significance in the field of bearing cage applications but has proven to be challenging. Herein, polyimide (PI) molding powder containing two kinds of PI with different rigidities is synthesized in situ to fabricate a two‐scale porous polyimide (PPI) by (cold and hot) isostatic pressing. The unique two‐scale porous structure originates from the bimodal particle size distribution of the PI molding powder. The oil stored in the two‐scale PPI is gradually thrown out as the rotation speed increases, which makes the two‐scale PPI suitable for bearing cages with a wider rotation speed range and realize persistent and stable oil supply under different speeds. The porosity of PPI decreases with increasing pressure during hot isostatic pressing, but the effect of temperature on the porosity is not obvious. Moreover, the two‐scale PPI maintains good mechanical properties, and its ring tension is as high as 22.3 MPa. Due to the high oil content (&gt;15%) and excellent oil retention rate (93.3%, at 3000 rpm for 180 min), the two‐scale oil‐containing PPI exhibits a stable low friction coefficient (≈0.096) and ultralow wear rate (≈0.6810−6mm3 (Nm)−1).

Genesis of Superlow Friction in Strengthening Si-DLC/PLC Nanostructured Multilayer Films for Robust Superlubricity at Ultrahigh Contact Stress.

Diamond-like carbon (DLC) films have significant potential to provide solutions for the friction reduction and the lubricity problem of mechanical moving friction pairs. However, the realization of excellent lubrication or even superlubricity and long lifetime under heavy loading conditions is still a great challenge, which is crucial for the applications of DLC in harsh environments. Here, we construct a group of property-strengthening Si-DLC/PLC multilayer films that could withstand ultrahigh contact stresses and achieve robust superlubricity. Under a peak Hertz contact stress of up to 2.37 GPa, the setup of a bilayer thickness of 324 nm enables the multilayered film (an overall film thickness of 1.53 μm) to achieve a superlow coefficient of friction toward 0.001 and an ultralow wear rate of 3.13 × 10-9 mm3/Nm. An alternating load reciprocating friction test emphasizes that this strengthening nanostructured Si-DLC/PLC multilayer possesses a kind of load self-adaptation because of its in situ nanoclustering transformation and local ordering of sp2-C phases at the sliding interface. The genesis of self-adaptation to the applied load is evaluated comprehensively to reveal its strengthening and toughening structural characteristics and robustness of the near-zero friction and wear features. The findings provide a significant design criterion for carbon-based solid lubricants applicable to harsh loading environments.

Macroscale superdurable superlubricity achieved in lubricant oil via operando tribochemical formation of fullerene-like carbon

Friction and wear are ubiquitous in moving mechanical assemblies, causing energy and equipment loss and producing harmful emissions. Mitigation efforts have long relied on oil-based lubricants, but challenges remain in achieving concurrent ultralow friction and wear without oil additives. Here, we demonstrate that a dual-phase TiB2-MoS2 film lubricated by oil without additives exhibits superdurable superlubricity characterized by a vanishingly small friction coefficient (0.007) and ultralow wear rate (10−9 mm3N−1m−1) maintained in lubricants over an unprecedentedly long sliding distance without performance deterioration. We identify a tribochemical route for the decomposition of oil molecules catalytically activated by the TiB2-MoS2 film, leading to operando formation of fullerene-like carbon that leads to diminished friction. First-principles calculations unveil strong stress responses of a TiB2 structural framework under wear strains, offering insights into the ultralow wear rate. These findings showcase a promising strategy to develop high-performance superlubricating materials that meet stringent conditions for demanding applications.

Independently tuning surface and subsurface reinforcement to optimize PTFE wear

Recent studies have shown that PTFE achieves ultra-low wear rates through a combination of surface and subsurface reinforcement. However, these two wear-reducing effects depend on filler material, size, and loading in ways that have proven difficult to isolate and study to date. In a recent study, we used 5 wt% of a secondary subsurface reinforcing phase (PEEK) to independently isolate and optimize surface reinforcement by trace nanofillers. To our knowledge, these hybrid composites are the first to demonstrate optimal wear reducing effects of nanofillers at trace loading (« 1 wt%). The present study independently varied PEEK and nanofiller loading to optimize both subsurface and surface reinforcement, respectively. In the absence of nanofillers, a minimum wear rate of 8 × 10−8 mm3/Nm was achieved at 20 wt% PEEK, which is 4-fold the loading used in our prior study. The addition of 0.1 wt% nano-alumina reduced the wear rate by 5-fold to 1.6 × 10−8 mm3/Nm. For all PEEK loadings, the addition of 0.1 wt% nanofiller reduced the corresponding PEEK-PTFE wear rate by between 4 and 40-fold. Wear performance and tribofilm quality degraded monotonically with increased nanofiller loadings beyond 0.1 wt% at all PEEK loadings. This study shows that surface and subsurface reinforcement are separable and independently tunable using fillers whose sizes and loadings differ by orders of magnitude. Conversely, it suggests that prior optima from single-filler-in-PTFE studies reflect a compromise between surface and subsurface reinforcement rather than an optimum of either.

Mo-doped Cr-Ti-Mo ternary o-MAX with ultra-low wear at elevated temperatures

In this work, the Cr-Ti-Mo ternary o-MAX ceramics based on the Cr2TiAlC2 phase are synthesized, and their tribological performance at elevated temperatures up to 800 ºC in the air is evaluated. With Si3N4 as a tribocouple, an unexpected ultra-low wear rate reaching 6.1 × 10−8 mm3 N−1 m−1 is observed in Cr1.9Ti0.9Mo0.2AlC2 at 800 ºC, accompanied by a stable coefficient of friction (COF) around 0.33 in a wide temperature range. X-ray photoelectron spectroscopy (XPS) depth profiling confirms a tribofilm with gradient composition, which simultaneously offers fluid lubricating at elevated temperatures and self-healing after cooling. Particularly, confirmed by the theoretical simulations, the doping of Mo improves the interlayer binding as well as alters the oxidation behaviors of Cr2TiAlC2. With an optimal interlayer binding strength and oxidation rate, the Cr1.9Ti0.9Mo0.2AlC2 can generate a tribofilm possessing ideal composition, which simultaneously promotes lubrication and anti-wear performance at elevated temperatures.

Ceramic-on-Ceramic Bearings in Total Joint Arthroplasty. Part 1

Summary. Ceramic bearings were first employed as alternatives to polyethylene (PE) bearings in total joint arthroplasty about a decade after Sir John Charnley introduced the first durable total hip arthroplasty (THA) with a metal-PE articulation. Charnley’s approach was based on a metal stem bonded to bone with polymethylmethacrylate (PMMA) and an acetabular component made of ultra-high-molecular-weight PE (UHMWPE). Microscopic particulate debris in the joint space from bearing wear has been shown to lead to periprosthetic inflammation, osteolysis, and implant loosening. Cross-linking can reduce the wear of UHMWPE, but it also compromises UHMWPE’s mechanical properties. Accordingly, there are concerns related to potential brittleness if UHMWPE implants are not positioned optimally. Also, the smaller particles generated from cross-linked UHMWPE may present an increased particulate load in vivo. Thus, there is a need for data on the long-term outcomes of cross-linked UHMWPE. Any technology that can reduce bearing wear rates in THA and total knee arthroplasty (TKA) can potentially decrease the morbidity and risks associated with premature revision surgery related to wear. Improved wear resistance also allows the use of large-diameter femoral heads in THA, leading to increased arc of movement and less risk of prosthesis dislocation. The ideal joint bearing for THA and TKA would be able to withstand high cyclic loading for several decades without undergoing corrosion or fretting at modular metal tapers, and would possess proven biocompatibility and material stability in vivo, as well as ultralow wear rates. The search for the ideal total joint bearing has led to the development of ceramic bearings.