Improving tribological properties and machining performance of a-C coatings by doping with titanium

In this study, a-C:Ti _x% coatings with various levels of Ti addition are deposited on cemented tungsten carbide (WC-Co) substrates using a medium-frequency twin magnetron sputtering and unbalanced magnetron sputtering system. This study investigates the tribological properties of the coatings by conducting wear tests against an AISI 1045 steel counterbody under a cylinder-on-disk line contact wear mode using an oscillating friction and wear tester. Additionally, turning tests and high-speed through-hole drilling tests are performed on AISI 1045 steel counterbodies and PCB workpieces, respectively, to investigate the machining performance of coated turning cutters and microdrills. The a-C:Ti _x% coatings not only have improved tribological properties but also demonstrate enhanced machining performance. For sliding against the AISI 1045 steel counterbody under loads of 10 and 100 N, the results show that the optimal friction and wear resistance properties are provided by the a-C:Ti_13% and a-C:Ti_3% coatings, respectively. Meanwhile, the a-C:Ti_20% and a-C:Ti_51% coatings yield the optimal turning and drilling performance, respectively.     

Optimum Me-DLC coatings and hard coatings for tribological performance

In this study, hard coatings (TiN, TiCN, CrN, and CrCN) and Me-DLC coatings (Ti _x%-C:H and Cr _x%-C:H) were deposited on tungsten carbide (WC) substrate by multiarc physical vapor deposition (MAPVD) and unbalanced magnetron (UBM) sputtering, respectively. Counterbodies of the AISI 1045 steel cylinder and the AA7075T651 aluminum cylinder were used in the cylinder-on-disk, line-contact wear mode under dry condition; a counterbody of the AISI 52100 steel ball was used in the ball-on-disk, point-contact wear mode, under both dry and lubricated conditions. All wear tests were conducted with a reciprocating machine. After the tests, the most suitable coating for various counterbodies and test environments was selected. For the coating/1045 steel cylinder, the Ti_10%-C:H coating possesses excellent tribological characteristics. For the coating/7075T651 aluminum cylinder, hard coatings display excellent wear resistance. For the coating/steel ball, CrCN and CrN coatings display very little wear under both dry and lubricated conditions. On TiN and TiCN coatings, special wear mechanisms of material transfer, adhesion wear, and fatigue fracture occurred during initial tests under kerosene lubrication.     

Effect of hydrogen content in a-C:H coatings on their tribological behaviour at room temperature up to 150 °C

Hydrogenated amorphous carbon (a-C:H) coatings deposited onto steel substrates by plasma assisted CVD, using different precursor gases (1 < H/C ratio < 4) were tested for their tribological behaviour. The H content in these coatings ranged from 25 to 29 at.%. Fretting mode I tests were performed on different couples consisting of coated and/or uncoated first bodies. Some tests were performed after a heat treatment of the coatings. As-deposited a-C:H/corundum couples tested at 23 °C and 50% RH showed lowering of the coefficient of friction at increasing normal load. Graphitisation is taking place in sliding contacts at high normal loads. For a-C:H/corundum couples a clear minimum in the coefficient of friction was noticed at 100 °C for coatings containing 27 at.% H. The coefficient of friction recorded on such couples is high compared to the one recorded on as-deposited a-C:H/a-C:H couples. However for the a-C:H/a-C:H couple, a lowering of the coefficient of friction with increasing fretting test temperature was noticed. The decreasing coefficient of friction was accompanied by an increasing wear. Graphitisation is causing severe degradation of a-C:H coatings at high test temperatures. An energetic analysis of the wear is finally reported. It appeared that the wear volume recorded at RT on as-deposited a-C:H coatings varies linearly with the cumulative dissipated energy. The wear rate coefficient decreases with increasing H-content. A stabilization of the sp³ bonds with increasing H-content might explain this behaviour. Confirmation was found by performing high temperature fretting tests. Interesting is the finding that fretting tests at RT performed after a thermal treatment of a-C:H coatings at either 100 or 150 °C, show a friction and wear behaviour identical to the ones recorded on as-deposited coatings tested at RT.     

Structure and properties of selected (Cr–Al–N,TiC–C,Cr–B–N) nanostructured tribological coatings

The paper will present the state-of-art in the process, structure and properties of nanostructured multifunctional tribological coatings used in different industrial applications that require high hardness, toughness, wear resistance and thermal stability. The optimization of these coating systems by means of tailoring the structure (graded, superlattice and nanocomposite systems), composition optimization, and energetic ion bombardment from substrate bias voltage control to provide improved mechanical and tribological properties will be assessed for a range of coating systems, including nanocrystalline graded Cr_1−xAl_xN coatings, superlattice CrN/AlN coatings and nanocomposite Cr–B–N and TiC/a-C coatings. The results showed that the superlattice CrN/AlN coating exhibited a super hardness of 45 GPa when the bilayer period Λ was about 3.0 nm. Improved toughness and wear resistance have been achieved in the CrN/AlN multilayer and graded CrAlN coatings as compared to the homogeneous CrAlN coating. For the TiC/a-C coatings, increasing the substrate bias increased the hardness of TiC/a-C coatings up to 34 GPa (at −150 V) but also led to a decrease in the coating toughness and wear resistance. The TiC/a-C coating deposited at a −50 V bias voltage exhibited an optimized high hardness of 28 GPa, a low coefficient of friction of 0.19 and a wear rate of 2.37 × 10⁻⁷ mm³ N⁻¹ m⁻¹. The Cr–B–N coating system consists of nanocrystalline CrB₂ embedded in an amorphous BN phase when the N content is low. With an increase in the N content, a decrease in the CrB₂ phase and an increase in the amorphous BN phase were identified. The resulting structure changes led to both decreases in the hardness and wear resistance of Cr–B–N coatings.     

Preparation of a-C:H/a-C:H:Si:O and a-C:H/a-C:H:Si multilayer coatings by PACVD

Carbon based multilayer coatings were prepared by plasma assisted chemical vapor deposition (PACVD) using methane (CH₄) and hexamethyldisiloxane (HMDSO) or methane and tetramethylsilane (TMS) as precursors. These coatings were deposited in a modified plasma nitriding plant operated at relatively high working pressures of 20 Pa. The multilayer design consisted of a-C:H and a-C:H:Si:O or a-C:H and a-C:H:Si single layers, respectively. The number of single layers and the material of the top layer were varied at constant total coating thicknesses. These multilayer coatings were investigated with regard to their morphology and composition as well as indentation hardness, abrasive wear, lubricant free friction and wetting behavior via contact angle measurements. The multilayer coatings exhibited lower wear rates and higher hardness values than a-C:H:Si:O or a-C:H:Si single layers and lower friction coefficients than pure a-C:H coatings under unlubricated test condition. Utilizing duplex processes, combining plasma nitriding pre-treatment and a following coating deposition, the adhesion of the multilayer coatings on high speed and cold working steel substrates could be considerably improved.     

The nanostructure, wear and corrosion performance of arc-evaporated CrBxNy nanocomposite coatings

The composition, nanostructure, tribological and corrosion behaviour of reactive arc evaporated CrB_xN_y coatings have been studied and compared to CrN. The CrB_xN_y coatings were deposited on a commercial Oerlikon Balzers RCS coating system employing 80:20 Cr:B targets. To vary the composition, the nitrogen fraction was adjusted (N₂ fraction = N₂/(Ar + N₂)) and a moderate bias voltage of − 20 V was applied during coating growth. The coating composition and nanostructure was determined using time-of-flight elastic recoil detection analysis (TOF-ERDA), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Ball-on-disc dry sliding wear tests were conducted using an alumina ball counterface both at room temperature and at 500 °C with the relative humidity controlled at 20%. Potentiodynamic corrosion tests were undertaken in 3.5% NaCl aqueous solution. The wear tracks were examined using optical profilometry and scanning electron microscopy (SEM); the surface composition inside and outside of the wear tracks were investigated using Raman spectroscopy and XPS. All coatings exhibit nanocomposite structures and phase compositions which are in fair agreement with those expected from the equilibrium phase diagram. The lowest wear rate at room temperature and 500 °C was found for CrB_0.14N_1.14, which was shown to exhibit the highest hardness and possesses a nanocomposite nc-CrN/a-BN structure. CrB_0.12N_0.84 coatings showed the lowest passive current density in potentiodynamic corrosion tests.     

Microstructure and mechanical properties of W-C:H coatings deposited by pulsed reactive magnetron sputtering

Reported are results of microstructure, mechanical and tribological properties studies for thin, amorphous hydrogenated carbon based coatings with tungsten content from 4.7 at.% up to 10.3 at.%. Studied coatings have been deposited by pulsed, reactive magnetron sputtering on substrates under planetary rotation. Resulting coatings, characterized by transmission electron microscopy (TEM) also at high resolution (HREM), show multilayer structure consisting of sub-layers of W-C:H type, with alternately high and low tungsten concentration. Thickness and number of sub-layers depend on rotation speed of planetary substrate holder. An average tungsten concentration decreases with increasing partial pressure of reactive gas (C₂H₂) during deposition. More insight into the microstructure of coatings provided HREM analysis showing crystalline precipitations of about 1-2 nm in size as well as tungsten-rich and tungsten-poor W-C:H sub-layers. Raman spectra confirm presence of amorphous, hydrogenated carbon (a-C:H) phase in the coatings. Microhardness of studied coatings depends on tungsten content and increases from 10.7 GPa to 13.7 GPa, for 5.1 at.% and 10.3 at.% of tungsten content, respectively. The highest cracking resistance and best adhesion (L_c2 = 78 N and HF1) has been achieved for coatings containing 4.9 at.% of tungsten and a sub-layer thickness of 5 nm. Tribological processes occurring in the coating-coating contact zone are dominated by graphitization and oxidation of W-C:H coating. Very low friction coefficient (0.04) and low wear rate seems to be an effect gaseous micro-bearing by tribo-generated carbon oxides and methane as well as hydrogen released from the coating. In the W-C:H-steel contact zone a tribo-layer composed of iron and tungsten oxides mixed with graphite-like products is growing at the surface of steel counterpart. This tribo-layer becomes a barrier restricting direct contact of steel with the coating and thus preventing it from further intense wear.     

Effect of the addition of crystalline β-phase in Al-Cu-Fe quasicrystalline coatings on their tribological properties

We investigate tribological properties (friction coefficient, wear, and adhesion force with fretting tests) of both quasicrystalline (Ψ-phase) and dual-phase (Ψ + β-cubic phases) Al-Cu-Fe coatings produced by electron-beam physical vapour deposition. Performed standard pin-on-disk tests (using bear steel pin and a load of 2 N) indicate that both quasicrystalline and dual-phase (Ψ + β) Al-Cu-Fe coatings exhibit close values of the friction coefficient (≈ 0.2-0.3) in vacuum. At the same time, the wear rate of the dual-phase coating is found to be essentially lower than that of quasicrystalline coating. It is demonstrated also that the value of the adhesion between the coating and the steel counterpart under fretting depends on the coating structure. The lowest adhesion is found to be observed for quasicrystalline coatings. Possible origins of the tribological behaviour of the coatings and their potential applications are discussed.     

Identification of the wear mechanism on WC/C nanostructured coatings

A series of WC/C nanostructured films with carbon contents ranging from 30 to 70 at.% was deposited on M2 steel substrates by magnetron sputtering of WC and graphite targets in argon. Depending on the amorphous carbon (a-C) incorporated in the coatings, nanocrystalline coating (formed mainly by WC_{1 − x} and W₂C phases) or nanocomposite (WC_{1 − x}/a-C) were obtained with tunable mechanical and tribological properties. Ultrahardness values of 36–40 GPa were measured for the nanocrystalline samples whilst values between 16 and 23 GPa were obtained in the nanocomposite ones depending on the a-C content. The tribological properties were studied using a pin-on-disk tester versus steel (100Cr6) balls and 5 N of applied load in dry sliding conditions and the failure modes by scratch adhesion tests. Three different zones were identified according to the observed tribological behavior: I (μ > 0.8; adhesive wear), II (μ: 0.3–0.6; abrasive wear) and III (μ ~ 0.2; self-lubricated). The wear tracks and the ball scars were observed by scanning electron microscopy (SEM) and Raman spectroscopy in order to elucidate the tribochemical reactions appearing at the contact and to determine the wear mechanism present in each type. A correlation among structure, crystalline phases, a-C content and tribomechanical properties could be established for the series of WC/C coatings and extended to understand the trends observed in the literature for similar coatings.     

Microstructure and tribology of TiC(Ag)/a-C:H nanocomposite coatings deposited by unbalanced magnetron sputtering

TiC(Ag)/a-C:H nanocomposite coatings with various Ag concentrations were fabricated on Si p(100) substrates. The composition and structure of as-deposited nanocomposite coatings were systemically investigated, and the friction and wear behaviors were also evaluated under the ambient, high temperature and high vacuum, respectively. Results show that the TiC nanocrystallites were formed in the amorphous hydrogenated carbon matrix near the substrate. The co-dopant Ag possessed nanocrystalline structure in the as-fabricated coatings whilst it formed Ag clusters (10–50 nm) on the surface. Furthermore, the introduction of Ag caused a significant reduction in the residual compressive stress without considerable decrease of the hardness and improved the adhesive strength of nanocomposite coatings. Tested as-deposited and after annealed at 500 °C coatings, the TiC(Ag)/a-C:H coatings showed a reduction of friction coefficients and wear rates with increment of Ag concentration. Under high vacuum condition, the TiC(Ag)/a-C:H coatings presented superlow friction behavior where the friction coefficient was reduced from 0.01 to 0.005 and lifetime increased from 0 to 1500 cycles. The significant improvement in tribological properties was mainly attributed to the low shear strength of Ag clusters on the surface as well as Ag diffusion to surface and wear track of coatings. The superior friction and wear behaviors of TiC(Ag)/a-C:H coatings make them good candidates as solid lubrication materials in space and aircraft applications.     

Controlling friction and wear of nc-WC/a-C(Al) nanocomposite coating by lubricant/additive synergies

Owing to increasing demands for reductions in emissions and improvements in fuel economy in the automotive industry, there is an urgent need to improve tribological performances of components. In the current paper, an nc-WC/a-C(Al) carbon-based nanocomposite coating was fabricated successfully via the magnetron sputtering process. The microstructure and mechanical properties of the as-fabricated nanocomposite coating were investigated. In particular, its friction and wear behaviors under poly-alpha-olefin oil lubricant added with anti-wear (AW), extreme-pressure (EP), or molybdenum dialkyldithiocarbamate (MoDTC) additive were systemically evaluated. Results show that the nc-WC/a-C(Al) nanocomposite coating has a typical nanocrystallite/amorphous microstructure and good mechanical properties. The significant improvement in the tribological performance of the boundary-lubricated nc-WC/a-C(Al) coating is mainly attributed to the WS₂ or MoS₂ + WS₂-containing tribofilm when S-based EP or MoDTC additive was used. Superior tribological performance of nc-WC/a-C(Al) nanocomposite coating was achieved by lubricant/additive synergies, indicating its potential application as a protective coating for automotive tribo-components.     

Comparison of hardmetal and hard chromium coatings under different tribological conditions

Electroplated hard chromium and thermal spray hardmetal coatings are widely used in a variety of applications for wear protection of component surfaces. The two protective coating types are tested in direct comparison for tribological conditions of dry abrasive wear (Taber Abraser test) and dry oscillating wear load. Oscillating wear tests are carried out both with hardened 100Cr6 steel and alumina balls as counterbody. Different types of hardmetal coatings are imparted. Besides HVOF sprayed coatings also coatings sprayed by an APS gun with axial powder feed are tested. For HVOF spraying besides standard WC/Co(Cr) feedstock also coarse (d₅₀ = 5 μm) and fine carbide feedstock (d₅₀ = 0.8 μm) and ultrafine powders, i.e. 2 μm < d < 12 μm, are considered. Use of ultrafine powders is particularly interesting from the economical point of view, as belt grinding can be sufficient for finishing in many cases. The optimum coating solution for wear protection depends on the specific tribosystem. The choice of feedstock, spraying process, equipment and processing conditions does not only depend on the resultant tribological properties. Therefore simultaneous influence on corrosion protection capability and thermal conductivity might have to be considered.     

Mechanical and tribological properties of multi-element (AlCrTaTiZr)N coatings

Multi-element (AlCrTaTiZr)N coatings are deposited onto Si and cemented carbide substrates by reactive RF magnetron sputtering in an Ar + N₂ mixture. The influence of substrate bias voltage, ranging from 0 to − 200 V, on the microstructural, mechanical and tribological properties of these nitride coatings is studied. A reduction in concentration of N and Al is observed with increasing substrate biases. The (AlCrTaTiZr)N coatings show the face-centered-cubic crystal structure (B1-NaCl type). The use of substrate bias changes the microstructure of the (AlCrTaTiZr)N coating from the columns with microvoids in boundaries to the dense and less identified columns. The compressive macrostress increases from − 0.9 GPa to − 3.6 GPa with an increase of substrate bias. The hardness and adhesion increase to peak values of 36.9 GPa and 60.7 N at the bias voltage of − 150 V, respectively. The tribological properties of the (AlCrTaTiZr)N coatings against 100Cr6 steel balls are evaluated by a ball-on-disc tribometer with a 10 N applied load. With an increase of substrate bias, the wear rate reduces while the friction coefficient almost keeps constant at 0.75. The lowest wear rate of 3.65 × 10^− 6 mm³/Nm is obtained for the (AlCrTaTiZr)N coating deposited at the bias voltage of − 150 V.     

Failure mechanisms of a hydrogenated amorphous carbon coating in load-scanning tests

A diamond-like carbon (DLC) coating with a top layer of pure hydrogenated amorphous carbon (a-C:H) and an interlayer of tungsten-modified hydrogenated amorphous carbon (a-C:H:W) was deposited onto polished cylindrical specimens of a hardened and tempered cold work tool steel. On a load-scanning test rig, tribological–mechanical tests under dry conditions with DLC coated specimens sliding against identical, but uncoated specimens were performed. Additionally, comparative tests with DLC sliding against DLC and tool steel sliding against tool steel were carried out. During each test cycle, the normal load was gradually increased from 13 to 350 N, corresponding to a Hertzian contact pressure of 1.0 to 3.0 GPa. The coefficient of friction was monitored as a function of the normal load, with a significant increase in friction indicating failure of the coating. The tests were repeated and stopped at different total numbers of load cycles. After the tests, a FIB-assisted microscopical analysis in terms of wear and damage of the DLC coating was performed, revealing the (subsurface) failure mechanisms. For DLC sliding against steel, the coating fails within only few load cycles; first tribologically and after that mechanically. Failure is initiated by adherence and subsequent transfer of steel of the counter body. Below adhered steel flakes, tensile cracks form in the a-C:H top layer, with sharp crack edges removing even more steel from the counter body. In following load cycles, coating fragments are being pulled out at these spots, representing the final failure mode. In contrast, for DLC sliding against DLC, no coating failure and also no significant wear are observed, even after a considerably higher number of load cycles.     

Effects of thickness and cycle parameters on fretting wear behavior of CVD diamond coatings on steel substrates

Diamond films have been grown on carbon steel substrates by hot filament chemical vapour deposition (CVD) methods. A Co-containing tungsten-carbide coating prepared by high velocity oxy-fuel spraying was used as an intermediate layer on the steel substrates to minimize the early formation of graphite (and thus growth of low quality diamond films) and to enhance the diamond film adhesion. The effects of thickness and cycle parameters on adhesion, tribological behaviour and electrochemical treatment of the diamond film were investigated. The diamond films exhibit excellent adhesion under Rockwell indentation testing (1500 N load) and in high-speed, high-load, long-time reciprocating dry sliding ball-on-flat wear tests against a Si₃N₄ counterface in ambient air (500 rpm, 200 N, 300000 cycles). Time modulated CVD (wherein the CH₄ fraction in the process gas mixture is cycled in time) is shown to yield diamond films offering an exceptional combination of low friction, high hardness, high wear resistance, as well as promising corrosion resistance.     

Preparation and characterisation of a-C and a-C:H coatings deposited by pulsed magnetron sputtering

The amorphous carbon coatings of a-C and a-C:H type were deposited by pulsed magnetron sputtering in argon and argon/acetylene atmosphere, respectively. The deposition rate, chemical composition, structure and mechanical properties of these coatings were studied as a function of acetylene flow rate. The adding of acetylene to working atmosphere caused increase of deposition rate and hydrogen content in coatings, and at the same time decrease in their hardness. The friction and wear behaviour of a-C and a-C:H coatings in ambient air are highly dependent on kind of counterparts material. The “true” friction coefficients of a-C and a-C:H coatings sliding against a-C and a-C:H coatings, respectively, are similar in values (0.06-0.08) and wear rates are similar too. Significantly higher friction coefficients (0.2-0.3) and wear rates were observed for both a-C and a-C:H coatings sliding against 100Cr6 steel. The lowest friction coefficients (0.02-0.04) and wear rates were obtained for a-C and a-C:H coatings sliding against Alumina counterpart.     

Mechanisms of self-lubrication in patterned TiN coatings containing solid lubricant microreservoirs

The tribological mechanisms of friction and lubrication have been investigated in TiN coatings patterned to contain microscopic reservoirs for solid lubricant entrapment. Photo-lithography was used to fabricate three sets of samples on silicon wafers, varying the reservoir size (4 and 9 μm) and spacing (11 and 25 μm), which resulted in samples with a nominal reservoir area of either 2 or 10%. Pin-on-disk tests were run using lubricants of graphite and indium and counterfaces of alumina and steel (440C). In most cases, the samples with the 9 μm holes spaced 25 μm apart gave the lowest friction coefficients and longest wear life. Analysis of the wear tracks by SEM/EDS methods showed carbon to be present in the holes of the graphite/steel counterface samples, but TiO₂ was found in the holes of the graphite/alumina counterface samples. For the indium/steel counterface samples indium was detected within the microreservoirs, but iron was also found, transferred from the ball. These experiments highlight a variety of tribological mechanisms that can operate in microreservoir-patterned coatings.     

Wear of CrC-coated carbide tools in dry machining

This paper discusses the tribological characteristics and cutting performance of chromium carbide (Cr_x%C)-coated carbide tool inserts and micron-drills in dry machining. Cr_x%C coatings have been deposited with different optical emission monitoring (OEM) set values, x%, of chromium target “poisoning” by unbalanced magnetron sputtering and OEM control. The microstructures and mechanical properties of Cr_x%C coatings have been measured by the experiments of scanning electron microscope (SEM), nanoindentation and adhesion. Experimental results indicate that the coating microstructure, mechanical properties and wear resistance vary according to OEM set values. Cr_10%C-coated inserts showed the best wear resistance in AISI 1045 steel turning test. Cr_50%C-coated tools have performed exceptionally well in both copper turning and printed circuit board (PCB) through-hole drilling tests. The service life of Cr_50%C-coated tool is four times higher than that of an uncoated tool in the PCB through-hole drilling test.     

TiN-Coating Effects on Stainless Steel Tribological Behavior Under Dry and Lubricated Conditions

The tribological properties of magnetron sputtered titanium nitride coating on 316L steel, sliding against Si₃N₄ ceramic ball under dry friction and synthetic perspiration lubrication, were investigated. The morphology of the worn surface and the elemental composition of the wear debris were examined by scanning electron microscopy and energy dispersive spectroscopy. TiN coatings and 316L stainless steel had better tribological properties under synthetic perspiration lubrication than under dry friction. Among the three tested materials (316L, 1.6 and 2.4 μm TiN coatings), 2.4 μm TiN coating exhibits the best wear resistance. The difference in wear damage of the three materials is essentially due to the wear mechanisms. For the TiN coating, the damage is attributed to abrasive wear under synthetic perspiration lubrication and the complex interactive mechanisms, including abrasive and adhesive wear, along with plastic deformation, under dry friction.     

The Tribological Performance of Surface Treated Ti6A14V as Sliding Against Si<Subscript>3</Subscript>N<Subscript>4</Subscript> Ball and 316L Stainless Steel Cylinder

Closed field unbalanced magnetron sputtering was used to deposit diamond-like carbon (Ti-C:H) coatings on Ti6Al4V alloy and gas nitrided Ti6Al4V alloy. Four different specimens were prepared, namely untreated Ti6Al4V alloy (Ti6Al4V), gas nitrided Ti6Al4V alloy (N-Ti6Al4V), Ti-C:H-coated Ti6Al4V alloy (Ti-C:H/Ti6Al4V) and Ti-C:H-coated gas nitrided Ti6Al4V alloy (Ti-C:H/N-Ti6Al4V). The tribological properties of the four specimens were evaluated using a reciprocating wear tester sliding against a Si₃N₄ ball (point contact mode) and 316L stainless steel cylinder (line contact mode). The wear tests were performed in a 0.89 wt.% NaCl solution. The results showed that the nitriding treatment increased the surface roughness and hardness of the Ti6Al4V alloy and improved the wear resistance as a result. In addition, the Ti-C:H coating also improved the tribological performance of Ti6Al4V. For example, compared to the untreated Ti6Al4V sample, the Ti-C:H coating reduced the wear depth and friction coefficient by 340 times and 10 times, respectively, in the point contact wear mode, and 151 times and 9 times, respectively, in the line contact wear mode. It is thus inferred that diamond-like carbon coatings are of significant benefit in extending the service life of artificial biomedical implants.