Superior Tribological Properties Research Articles

Tribological Properties of Several Surface-Modified Piston Rings Under Extreme Conditions

Abstract This article explores the performance of different commercial piston rings when matched with a boron-phosphorus (BP) alloy cast iron cylinder liner, specifically in high-power density diesel engines. The focus is on the friction, wear, and scuffing characteristics. An interrupted wear test was conducted under lean oil conditions to study the scuffing behavior of plated Cr-diamonds coating (GDC) and diamond-like carbon coating (DLC). The findings reveal that DLC coatings exhibit superior tribological properties, displaying low friction coefficients and wear loss at temperatures of 150 °C and 240 °C. In contrast, GDC coatings demonstrate relatively poor performance. Additionally, the DLC coating demonstrates excellent scuffing resistance, as no material transfer was observed for up to 77 min, even without lubrication. The interrupted scuffing test reveals that the scuffing process undergoes a stable wear stage, followed by a sudden drop and subsequent increase in friction force, ultimately resulting in scuffing when the BP cylinder is paired with GDC. On the other hand, although the frictional force of DLC initially increases after a brief decline, no significant adhesive wear is observed. This can be attributed to the formation of a tribo-chemical layer of carbides, which effectively prevents scuffing. In comparison to traditional methods of postwear morphology and analysis, our proposed interrupted scuffing tests offer enhanced capabilities for evaluating the wear condition of friction pairs at various time intervals during the oil depletion process. This novel approach introduces a new paradigm for investigating wear patterns in different friction pairs.

Effects of power on tribological and mechanical properties of diamond-like carbon-film-modified rubber

This study aims to improve the wear resistance of nitrile butadiene rubber (NBR) by depositing diamond-like carbon (DLC) films using direct-current magnetron sputtering (DC-MS), a simple and cost-effective technique. DC-MS is a coating process that uses a direct current to generate an electric field and sputter conductive materials from a target to a substrate. A magnetic field enhances the plasma density and sputtering rate. This study examines the bonding force, surface morphology, tribological properties and mechanical strength of DLC. Scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy are used to characterize the cross-sectional morphology, structural features and chemical bonding species of DLC films and NBR substrates. The nanoindentation results show that varying the power has no significant effect on hardness and Young’s modulus. Tribological tests are conducted under ambient conditions using a ball-and-disk tribometer, with a fixed load of 0.3 N. The results indicate that the power of DLC films influences their tribological properties. Specifically, DLC films prepared at 120 W exhibit superior tribological properties, maintaining a stable coefficient of friction below 0.2 for the test duration. These findings have promising implications for application of DLC films.

Study of the Effect of ZnO Functionalization on the Performance of a Fully Formulated Engine Oil.

The automotive sector is demanding higher specifications to achieve maximum efficiency; in this sense a new generation of lubricants with higher thermo-oxidative stability and superior tribological properties is being explored. The formulation of nanolubricants based on the nature of different nanomaterials is one of the most recent approaches, with several gaps to cover, such as dispersion stability, related to the compatibility of proposed nanomaterials with conventional additives and baseoils used in lubricant formulation. This study evaluated the effect of ZnO nanomaterial dispersed in a commercial engine oil using two different approaches; the use of surfactant and nanomaterial surface functionalization to promote higher stability and lower cluster size. Experimental evidence shows a synergetic effect between the tribological protection mechanism and the antioxidant properties in the lubricant. The effect of nanoparticle cluster size, functionalization level, and nanomaterial content are presented.

Graphite-like carbon films catalytically grown on a carburized substrate with an antenna structure at the interface: Experiments and first-principles calculations

This article reports a novel process to produce high-performance GLC films on steel substrate by successive steps in a plasma nitriding system. Different from those made by conventional PVD/CVD, the GLC film reported here was grown on carburized/carbonitrided steel surface involving catalytic reactions. An antenna structure was observed at the interface with the substrate, which benefits the GLC film with improved durability, since such a structure could block or split cracks, leading to elevated adhesion strength and resistance to spallation. With combined experiments and first-principles calculations, we demonstrate that Fe3C has a stronger catalytic effect on GLC films than Fe3C(N), and the GLC films grown on carburized layers are thicker with stronger bonding and superior tribological properties due to the beneficial structure at the interface. The findings demonstrate a simple and low-cost method to produce high-performance GLC films via catalytic growth and interface matching mechanisms.

Investigation on microstructure and tribological performances of electrodeposited Ni-W-Y2O3 composite coatings

Nickel-tungsten-yttrium oxide (Ni-W-Y2O3) composite coatings were co-electrodeposited onto low-carbon steel surfaces using the direct current electrodeposition method with a constant current density of 2 A/dm2. The influence of Y2O3 nanoparticles on the microstructure, morphology, microhardness and tribological performance of the composite coatings was investigated. The incorporation of Y2O3 nanoparticles was found to significantly refine the crystallite size of the coatings. The microhardness improvement and superior tribological properties of the Ni-W-Y2O3 composite coatings were attributed to the dispersion strengthening and refine crystalline strengthening effects induced by the addition of Y2O3 nanoparticles. It was also observed that the coating prepared from an electrolyte containing 10 g/L Y2O3 nanoparticles exhibits the highest wear resistance. These results highlight the potential of Y2O3 nanoparticles as a promising additive for enhancing the mechanical and tribological properties of coatings.

Nickel metal matrix composites reinforced with solid lubricants: A comprehensive review

Nickel metal matrix composites are suitable for aerospace and military applications due to their superior mechanical and tribological properties. The incorporation of reinforcing components in the nickel metal matrix composites significantly improves the specific strength, microhardness, wear resistance, frictional behavior, creep, and fatigue characteristics, as well as provides exceptional surface quality in comparison to typical engineering materials. The current study attempted to explore a review on nickel composites reinforced with various solid lubricants, along with their pros and cons. The study focuses on the issues like interfacial transition, agglomerating activity, and non-uniform particle dispersion. Several studies have been conducted to highlight the effect of solid lubricants on the microstructure, mechanical and tribological characteristics such as tensile strength, yield strength, ductility, hardness, friction, wear, and fatigue. In this review, the principal applications of various nickel matrix composites are also thoroughly examined.

Se Nanopowder Conversion into Lubricious 2D Selenide Layers by Tribochemical Reactions.

Transition metal dichalcogenide (TMD) coatings have attracted enormous scientific and industrial interest due to their outstanding tribological behavior. The paradigmatic example is MoS2 , even though selenides and tellurides have demonstrated superior tribological properties. Here, an innovative in operando conversion of Se nanopowders into lubricious 2D selenides, by sprinkling them onto sliding metallic surfaces coated with Mo and W thin films, is described. Advanced material characterization confirms the tribochemical formation of a thin tribofilm containing selenides, reducing the coefficient of friction down to below 0.1 in ambient air, levels typically reached using fully formulated oils. Ab initio molecular dynamics simulations under tribological conditions reveal the atomistic mechanisms that result in the shear-induced synthesis of selenide monolayers from nanopowders. The use of Se nanopowder provides thermal stability and prevents outgassing in vacuum environments. Additionally, the high reactivity of the Se nanopowder with the transition metal coating in the conditions prevailing in the contact interface yields highly reproducible results, making it particularly suitable for the replenishment of sliding components with solid lubricants, avoiding the long-lasting problem of TMD-lubricity degradation caused by environmental molecules. The suggested straightforward approach demonstrates an unconventional and smart way to synthesize TMDs in operando and exploit their friction- and wear-reducing impact.

Performance of Polymer Composites Lubricated with Glycerol and Water as Green Lubricants

The study analysed the tribological performance of five different polymer composites: polyetheretherketone reinforced with 30% carbon fibres—PEEK CF30, polyetheretherketone reinforced with 10% carbon fibres, 10% graphite and 10% polytetrafluoroethylene—PEEK MOD, polytetrafluoroethylene reinforced with 25% carbon fibres—PTFE CF25, polyoxymethylene with 30% carbon fibres—POM CF30 and ultra-high molecular weight polyethylene—UHMW PE. The polymers were tested under the sliding regime of a reciprocating stainless-steel ball on a polymer disc, with test parameters expected for hydraulic valves. Two environmentally safe lubricants were used: glycerol and water. The selected polymer materials and their tribological properties were compared based on the coefficient of friction and the specific wear rate. The worn surfaces were examined using scanning electron microscopy, and the transfer film was analysed using the energy dispersive spectroscopy technique. When tested in glycerol, a comparable and low coefficient of friction was measured for all polymers (~0.02). At the same time, a significantly lower coefficient was measured for all polymers in glycerol compared to water-lubricated conditions (~0.06–0.22). The polymers differed in the measured specific wear rate, which increases significantly in water for all polymers. A lower specific wear rate was measured for three polymers with higher microhardness: PEEK CF30, PEEK MOD and POM CF30. In water, PEEK CF30 showed superior tribological properties under harsh conditions but was well followed by POM CF30, which showed the most intense transfer film.

ZnO-Doped gC3N4 Nanocapsules for Enhancing the Performance of Electroless NiP Coating-Mechanical, Corrosion Protection, and Antibacterial Properties.

A carbon nitride (C3N4) nanomaterial has superior mechanical, thermal, and tribological properties, which make them attractive for various applications, including corrosion-resistant coatings. In this research, newly synthesized C3N4 nanocapsules with different concentrations (0.5, 1.0, and 2.0 wt %) of ZnO as a dopant were incorporated into the NiP coating using an electroless deposition technique. The nanocomposite coatings either ZnO-doped (NiP-C3N4/ZnO) or undoped (NiP-C3N4) were heat-treated at 400 °C for 1 h. The as-plated and heat-treated (HT) nanocomposite coatings were characterized by their morphology, phases, roughness, wettability, hardness, corrosion protection, and antibacterial properties. The results indicated that the microhardness of as-plated and heat-treated nanocomposite coatings was significantly improved after the incorporation of 0.5 wt % ZnO-doped C3N4 nanocapsules. The outcomes of electrochemical studies revealed that the corrosion resistance of the HT coatings is higher than the corresponding as-plated ones. The highest corrosion resistance is achieved on the heat-treated NiP-C3N4/1.0 wt % ZnO coatings. Although the presence of ZnO in the C3N4 nanocapsules increased its surface area and porosity, the C3N4/ZnO nanocapsules prevented localized corrosion by filling the microdefects and pores of the NiP matrix. Furthermore, the colony-counting method used to evaluate the antibacterial behavior of the different coatings demonstrated superior antibacterial properties, namely, after heat treatment. Therefore, the novel perspective C3N4/ZnO nanocapsules can be utilized as a reinforcement nanomaterial in improving the mechanical and anticorrosion performance of NiP coatings in chloride media, together with providing superior antibacterial properties.

Optimization of Wear Process Parameters of Al6061-Zircon Composites Using Taguchi Method

Aluminium metal matrix composites are utilised extensively in a variety of engineering applications, including those involving automobiles, aerospace, and other fields of engineering because of its superior tribological properties. In the present research work, an effort was made to investigate the wear behaviour of an aluminium alloy called Al6061 that was manufactured by a process called two-step stir casting. The alloy was strengthened with zircon particles. The zircon particles were varied in three different percentages: six percent, nine percent, and twelve percent. A pin-on-disc wear testing machine was used to investigate the wear behaviour of Al6061-Zircon composites at elevated temperature 100°C. Experiments were performed as per the design of the experiments that had been generated using Taguchi’s method. In order to do the analysis on the data, L27 Orthogonal array was chosen. During the wear process, an investigation was conducted to determine the impact of applied load, speed, percentage of reinforcement, and sliding distance on the wear response parameter. An analysis of variance (ANOVA) table and a regression equation were established to facilitate this study. In order to conduct the study of the dry sliding wear resistance, the aim of this equation was to select the smallest possible features. The scanning electron micrographs of Al6061-Zircon composites show the presence of zircon particles. It also shows that the particles are distributed uniformly in the Al6061 matrix. The scanning micrographs of worn out surfaces of Al6061-Zircon composites show the presence of grooves on the wear surface moving parallel to the sliding direction. According to the outcomes, the factor with the major impact is the load, followed by speed, sliding distance, and the percentage of reinforcement. In conclusion, confirmation tests were conducted in order to validate the experimental results.

Effect of different volume ratios of SiC and TiO2 reinforcement particles on mono and hybrid surface composites of AA7075-T651 through friction stir processing

In the present work, the different volume ratios of silicon carbide and titanium dioxide particles were incorporated with AA7075-T651 to improve the surface properties using multipass friction stir processing. The metallurgical study of the friction stir processed samples was examined through optical microscopy and field emission scanning electron microscopy with energy-dispersive X-ray analysis. In addition, the microhardness, wear, and corrosion properties were measured and analyzed. The results revealed that the increased amount of SiC particles caused uniform particle dispersion and was devoid of cluster-rich regions within the matrix. The increased volume of SiC particles exhibited a smaller grain size due to higher grain refinement. The sample with 100% SiC showed superior mechanical, tribological, and corrosion properties. The microhardness of sample with 100% SiC was increased by 13.60% compared to base metal, it was also better compared to other composite samples. Similarly, the coefficient of friction, wear rate, and corrosion resistance properties were reduced by 43.24%, 14.98%, and 75%, respectively.

Achieving superior tribological properties of GNPs reinforced Ti6Al4V composites via interface structure design

The severe interface reaction, which has been a challenging problem in graphene nanoplatelets (GNPs) reinforced Ti6Al4V (TC4) matrix composites, results in poor mechanical and tribological properties. Herein, GNPs/TC4 composites exhibited excellent wear resistance by introducing the in-situ TiB whiskers (TiBw) on the interface between GNPs and matrix. This work highlights the mechanical and tribological properties of GNPs/TC4 composites by diminishing the interface reaction and strengthening the interface bonding through the in-situ formed TiBw.

Nitrogen-Doped Carbon Dot as a Lubricant Additive in Polar and Non-polar Oils for Superior Tribological Properties via Condensation Reaction.

Nitrogen-doped lubricating additives have been proved to be an effective strategy to improve the tribological properties of lubricating oil. However, the traditional preparation methods of nitrogen-doped lubricating additives have the defects including harsh preparation conditions and a time-consuming preparation process. Herein, we report a preparation method of nitrogen-doped carbon dot (NCD) lubricating additives in a short time by one-step aldehyde condensation reaction at room temperature. The small size effect and nitrogen-containing functional groups of NCD lubricating additives provide favorable conditions for their dispersion and low friction in base oil. The tribological properties of NCD lubricating additives in sunflower oil (SFO) and PAO10 were systematically evaluated. The results show that NCD lubricating additives could reduce the average friction coefficient of SFO from 0.15 to 0.06 and PAO10 oil from 0.12 to 0.06, and the wear width is also decreased by 50-60%. In particular, the friction curve is very stable, and the friction coefficient was maintained at about 0.06 even under the working time of 5 h. By analyzing the morphology and chemical properties of the worn surface, the lubrication effect of NCDs is attributed to its small size effect and adsorption, which was easy to enter the friction gap to fill and repair. Furthermore, the doping of nitrogen induces the occurrence of friction chemical reactions, forming a friction film of nitrides and metal oxides at the friction interface, which effectively reduces the friction and wear of the surface. These findings provide a possibility for the convenient and effective preparation of NCD lubricating additives.

Effects of sintering temperature on the microstructure, mechanical, tribological and thermophysical properties of GNPs/IN738 composite

While IN738 Ni-based superalloy is a high strength alloy, it is feasible to improve its properties at the bulk level by reinforcing with graphene nanoplatelets (GNPs), taking advantage of the superior mechanical, tribological and thermal properties using the spark plasma sintering technique. In the present study, the influence of spark plasma sintering temperature range between 900 and 1100 °C on the microstructure, mechanical, tribological and thermophysical properties of GNPs/IN738 composite is assessed. The dispersion of GNPs reinforcement and alloying metals to form composite powder is conducted using a turbular mixer and low-frequency planetary ball milling, followed by spark plasma sintering. The relative density of the sintered samples assessed following Archimedes' method indicates increasing densification with the increasing sintering temperature from 94.7% (900 °C) to 98.5% (1100 °C). The microstructure assessed via SEM, XRD and Raman spectroscopy indicates the formation of precipitate gamma, intermetallic gamma prime, solid solution and GNPs strengthening phases. Thus, the mechanical (micro/nano hardness and Young's modulus), tribological (wear rate and coefficient of friction), and thermophysical (thermal diffusivity, thermal conductivity, and specific heat capacity) properties increased with the increasing sintering temperature. The microhardness increased from 354HV (900 °C) to 469HV (1100 °C), nanohardness from 8 GPa (900 °C) to 17 GPa (900 °C), and Young's modulus from 190 GPa (900 °C) to 291 GPa (1100 °C). The wear rate reduced with an increase in sintering temperature for the three loads of 5, 10 and 20N. The thermophysical properties assessed from 25 to 600 °C show the formation of few inflection points as the temperature increases, which is attributed to the dissolution and rearrangement of precipitate gamma prime and Cr in solid solution phases. Similarly, the small increment in the thermal diffusivity is equally associated with the smoother phonon transition at the GNPs/matrix interface.

Impact of Using Tungsten, Cobalt, and Aluminum Additives on the Tribological and Mechanical Properties of Iron Composites

The effect of tungsten, aluminum, and cobalt on the mechanical properties of iron-based composites prepared by powder technology was studied. Five samples with different contents of tungsten, aluminum, and cobalt were established. The five samples have the following chemical compositions: (I) full iron sample, (II) 5wt.% tungsten, (III) 5wt.% tungsten-4wt.% cobalt-1wt.% aluminum, (IV) 5wt.% tungsten-2.5wt.% cobalt-2.5wt.% aluminum, and (V) 5wt.% tungsten-1wt.% cobalt-4wt.% aluminum. The mixed composite powders were prepared by mechanical milling, in which 10:1 ball to powder ratio with 350 rpm for 20 h was cold compacted by a diaxial press under 80 bars, then sintered at temperatures ranging from 1050 °C to 1250 °C in an argon furnace. The samples were characterized mechanically and physically using XRD, SEM, a density measuring device, a hardness measuring device, a compression test device, and a tribological device for wear and friction tests. XRD results refer to the formation of different intermetallic compounds such as Fe7W6, Al5Co2, Fe2W2Co and Co7W6 with the main peaks of Fe. The good combination of tribological and mechanical properties was recorded for sample number five, which contained 5% W, 4% Al, 1% Co and Fe base, where it obtained the highest wear resistance, largest hardness, acceptable compressive strength, and lowest friction coefficient due to the good combination of hard and anti-friction intermetallic action compared with the other samples. This sample is a good candidate for applications which require high wear resistance and a moderate friction coefficient accompanied with high toughness, like bearing materials for both static and dynamic loading with superior mechanical and tribological properties.

Superior mechanical and tribological properties of short-cut carbon fiber reinforced monomer casting nylon composites after heat treatment

The effect of oil and water treatment with respect to the mechanical and tribological properties of short-cut carbon fiber (SCF)/monomer casting (MC) nylon composites was investigated. It was found that both the oil and water treatment can improve the crystallinity of SCF/MC nylon composites. The tensile strength and impact strength of oil treatment composites increase and the friction coefficient and the volumetric wear decrease. In addition, the water treatment is not as effective as oil treatment in improving material properties. This work would provide significant guidance for the preparation and post-treatment of SCF/MC nylon composites with excellent properties. It is also a useful attempt to develop new composite materials further to meet the needs of certain special spiral drives.

Reproduction of Nanofluid Synthesis, Thermal Properties and Experiments in Engineering: A Research Paradigm Shift

The suspension of different nanoparticles into various conventional thermal fluids to synthesize nanofluids has been proven to possess superior thermal, optical, tribological, and convective properties, and the heat transfer performance over conventional thermal fluids. This task appears trivial but is complicated and significant to nanofluid synthesis and its subsequent utilization in diverse applications. The stability of mono and hybrid nanofluids is significantly related to stirring duration and speed; volume, density, and base fluid type; weight/volume concentration, density, nano-size, and type of mono or hybrid nanoparticles used; type and weight of surfactant used; and sonication time, frequency, mode, and amplitude. The effects of these parameters on stability consequently affect the thermal, optical, tribological, and convective properties, and the heat transfer performance of nanofluids in various applications, leading to divergent, inaccurate, and suspicious results. Disparities in results have inundated the public domain in this regard. Thus, this study utilized published works in the public domain to highlight the trend in mono or hybrid nanofluid formulation presently documented as the norm, with the possibility of changing the status quo. With the huge progress made in this research area in which a large quantum of different nanoparticles, base fluids, and surfactants have been deployed and more are still emerging in the application of these advanced thermal fluids in diverse areas, there is a need for conformity and better accuracy of results. Reproduction of results of stability, thermal, optical, tribological, anti-wear, and fuel properties; photothermal conversion; and supercooling, lubrication, engine, combustion, emission, thermo-hydraulic, and heat transfer performances of formulated mono or hybrid nanofluids are possible through the optimization and detailed documentation of applicable nanofluid preparation parameters (stirring time and speed, sonication duration, amplitude, mode, frequency, and surfactant concentration) employed in formulating mono or hybrid nanofluids. This proposed approach is expected to project a new frontier in nanofluid research and serve as a veritable working guide to the nanofluid research community.

A minireview on nanofluids for automotive applications: Current status and future perspectives

• Nanofluids have superior thermophysical, rheological, and tribological properties. • Nanofluids can be applied as radiator coolant, engine fuel, and engine lubricant. • There exist several challenges for automotive applications of nanofluids. • Recommendations for automotive applications of nanofluids are disclosed. In view of the superior thermophysical, rheological, and tribological properties of nanofluids, they are applicable for heat transfer and lubrication in automobiles. Nanofluids in automobiles have possible applications such as a radiator coolant, engine lubricant, air conditioning system lubricant, engine fuel, brake fluid, and shock absorber. This review focuses on automotive applications of nanofluids. Details about the experimental reports on the various properties of nanofluids along with correlations for nanofluids have been specified. How nanofluids prove to be advantageous as well as the disadvantages of their use in automobiles are elaborated. Along with this, it emphasizes the challenges and future directions for nanofluids for each automotive application of nanofluids. It has been found that the stability of the nanofluids and the lack of sufficient data to provide proof hinder their way towards commercialization. Overall, there is still a lot of scope and need for research in nanofluid applications in the automotive area.

Study of the Influence of V, Mo and Co Additives on the Carbide Formation and Microhardness during Thermal Diffusion Chrome Planting of X35CrNi2-3 Steel

Saturation diffusion with chromium has not been adequately studied among all the surface thermochemical treatment (STCT) processes of steels. Especially, the complex saturation behavior when several elements are added directly for chemical treatment needs to be systematically studied. This work aims at determining the effect of V, Mo, and Co on the parameters of chromium thermal saturation diffusion (thickness, phase composition, microstructure, and microhardness) of the surface layer in X35CrNi2-3 steel. The process was carried out at a temperature of 1000 °C for 24 h. The results showed that complex structural chromium plating together with the addition of strong carbide-forming elements (V and Mo) has a significant effect on the phase composition of the fabricated layer, where the formation of VC and Mo2C carbides significantly increases the microhardness of the samples to 2000 HV and 2500 HV, respectively. On the other hand, the addition of Co with a less carbide-forming affinity has little effect on the phase composition of the coating, and nitride compounds predominated in the microstructure similar to the single-element chromium plating. The results indicate the possibility of improving and accelerating the traditional thermal chromium plating processes and opening up new horizons for obtaining gradient coatings with superior tribological properties.

Tribological behaviour of Ti/HA and Ti/SiO2 functionally graded materials fabricated at different strain rates

Functionally graded materials (FGMs) have found extensive applications in the biomedical industry, due to their excellent mechanical and tribological properties. However, new FGM fabrication techniques are yet to be examined for possible enhancements in their properties. This study investigates the tribological properties of Titanium/Hydroxyapatite (Ti-HA) and Titanium/Silicon oxide (Ti-SiO2) FGM samples fabricated by three die compaction techniques for the application of dental implants. The constituting powder particles were functionally dispersed and mixed using a newly-designed mixer and consolidated by hot dynamic and quasi-static compaction techniques at three different strain rates. Microstructure, hardness, wear resistance, wear penetration depth, and friction coefficient of the FGM samples were then studied in this work. Optical microscopy images exhibited smooth dispersion of powders conforming to a linear grading function. Vickers hardness values of the FGM samples was found to be directly proportional to the strain rate and inversely proportional to the content of the reinforcing phase (HA or SiO2). Higher strain rate also resulted in higher wear resistance and lower wear penetration depth in all FGMs, with the highest wear resistance being observed in the samples prepared using the Split Hopkinson Bar. Similarly, the coefficient of friction was also shown to be the lowest in Ti-HA samples prepared using Split Hopkinson Bar. Further, microscopic observations revealed that adhesion, delamination and abrasion as the dominant wear mechanisms in all FGM samples. It was concluded that the Ti-HA sample produced by the SHB method enjoyed superior tribological properties, being comparable to that of natural human teeth.