Coated Ti6Al4V Alloy Research Articles

Thermal analyses and weight gain modeling study on Ti–Al – based intermetallic coated Ti6Al4V alloy

Abstract Ti6Al4V alloy is a commonly used α + β alloy among titanium alloys. In this study, in order to improve the oxidation resistance of the Ti6Al4V alloy, Ti–Al – based aluminum coating was deposited to the surface by the pack cementation method. The aluminizing process was carried out in an open atmosphere oven at 700 °C for 4 and 6 h. It has been observed that the coating layer thickness varies between 13 and 17 µm depending on the duration of cementation process. From XRD analysis, it has been detected the TiAl3, TiAl2, and TiAl phases on the coating layer. Aluminum coated and untreated Ti6Al4V alloys were subjected to oxidation tests at 800, 850, and 900 °C for 4, 20, and 40 h. The obtained nonlinear weight gain characteristic has been modeled to determine the coating status of the samples. It was determined that the highest weight gain was in the untreated sample. Using the provided model, samples were classified in terms of coating condition by systematic approach based on weight gain profile versus time. Oxidation tests also supported with DTA and TG analyses.

Characterization and antibacterial activity of co-sputtered Cu-doped TiO2 coatings deposited on Ti6Al4V alloy

Copper has gained increased interest because of its important role in metabolism and antimicrobial activity. In this study, composite target material of Ti and Cu was used to deposit TiO2 coatings doped with copper on Ti6Al4V alloy. The aim was to examine the influence of the applied bias during the deposition of Cu-doped TiO2 coating by sputtering in a glow-discharge in a pure O2 atmosphere for a deposition time of 240 min. Different substrate values, selected from 0 to -150 V, were used in the process. The increase in bias voltage from -50 to - 150 V decreased the thickness of the oxide coatings and improved their adhesion to the substrate while increasing the Cu2O phase at the expense of a CuO phase decrease. Simultaneously, the increase in bias voltage decreased Cu content from about 32 wt% for the -50 V biased down to around 11 wt% for the -150 V biased specimens. The antimicrobial efficacy against E. coli estimated by direct contact experiments on the top of the uncoated (control) and coated Ti6Al4V alloy revealed about 94% inhibition for the -50V biased down to around 37% for the -150 V biased coatings as opposed to the control.

Effects of substrate roughness on the tribological properties of duplex plasma nitrided and MoS2 coated Ti6Al4V alloy

The poor surface shear resistance of Ti6Al4V alloy limits its applications involving moving components. To improve its tribological properties, a duplex treatment method involving plasma nitriding and MoS2 coating was proposed. The objective was to enhance load-bearing capacity, optimize surface roughness, and extend the lifetime of the MoS2 coating. Plasma nitriding significantly increased surface hardness by 2.3 times compared to untreated alloy. MoS2 coating on the hardened subsurface resulted in low friction coefficients of 0.05 at 25 % relative humidity. The duplex treated sample with a rough subsurface showed a lifetime of 11.90 h, six times better than the smooth subsurface sample. Higher subsurface roughness facilitated lubricant storage, release, and the formation of a continuous tribofilm, resulting in longer lifetime.

Comparison study of corrosion behavior for chitosan coated Ti6Al4V alloy produced by selective laser melting and forging

In recent years, the selective laser melting (SLM) technique has attracted widespread interest due to its ability to prepare biomedical materials with complex geometries, high dimensional accuracy and cost-effectiveness. However, Ti6Al4V alloy produced by SLM technique is faced with poor corrosion resistance and bio-inertness problems. Therefore, in this study, chitosan coatings were performed on Ti6Al4V alloy produced by electrophoretic deposition (EPD) forging (traditional method) and SLM for 15 min and 30 min. Corrosion behaviors of chitosan coated surfaces were compared by using electrochemical corrosion test method in simulated body fluid (SBF). The highest corrosion potential (Ecorr) values were −504 mV for forged and −592 mV for SLM on chitosan coated surfaces for 30 min. As a result, the chitosan coating showed that the Ti6Al4V alloy produced by the SLM technique increased the corrosion resistance. When the deposition time was 30 min, the resulting chitosan coating was about 1.4 order of magnitude than the untreated sample for the Ecorr value for both sample groups. Therefore, thanks to the biocompatible chitosan coating obtained by the EPD technique, the corrosion resistance of the surfaces produced using SLM has reached a level that can compete with forged surfaces.

Systematic microstructure modification effect on nanomechanical, tribology, corrosion, and biomineralization behavior by optimized anodic alumina nanotubes coated Ti–6Al–4V alloy

Electrochemical anodization is a cost-effective surface modification method that has been used in recent years not only for creating protective layers but also for the fabrication of porosity in biomedical applications. This method allows for the optimized fabrication of self-ordered nanotubular or nanoporous oxide structures. In this study, the structural characteristics, mechanism, adhesion, scratch hardness, wettability, nanoindentation, wear resistance, corrosion behavior, and in-vitro bioactivity of aluminum/alumina (Al/Al2O3) nanotube coating on Ti–6Al–4V (Ti64) were systematically studied. As the primary layer, a thin layer of pure Al was sputtered onto a Ti64 substrate via physical vapor deposition. Consequently, a dense and uniform Al2O3 nanotubes layer was fabricated as the second layer by anodization in a 0.35 wt% NH4F electrolyte solution (90 ethylene glycol:10 water) at 60 V (constant potential) for various durations, followed by optimization of the sealing to remove the oxide layer and transform the nanoporous into nanotubes. Optimized anodizing, sealing, and annealing resulted in a homogeneous nanotube structure with a mean diameter of 85 nm and a length of 1.58 μm. Systematic improvements in the adhesion, scratch hardness, nanoindentation, and wettability were achieved in each modification process. The corrosion rate and the coefficient of friction also reached 0.7297 × 10−1 (mm year−1) and 0.208 (load of 10 N) after 1 h of anodization and 30 min sealing followed by annealing at 450 °C, respectively. When a thick apatite layer with the desired Ca/P ratio was created on the annealed Al2O3 nanotube structure, an excellent improvement in surface bioactivity was demonstrated.

Optimisation on machining parametres by EDM of TiN coated Ti6Al4V alloys

ABSTRACT This study investigated the effects of electro-erosion (EDM) processing parameters on TiN-coated Ti6Al4V alloy by the physical vapour deposition (PVD) technique. Electrode wear rate (TWR), workpiece machining rate (MRR), and surface roughness (Ra) values were determined by including discharge current, pulse time (ton), and two different tool electrodes (E-Cu and CuBe) into the EDM process parameters. Variables affecting the experimental study (ANOVA) were performed depending on the analysis of variance method. For the analysed (ANOVA) TiN-coated Ti6Al4V samples, the most optimal parameters of MRR value were determined using current 12 A, ton 100, and Cu electrodes. For the TWR value, the optimum parameters were examined by using current 6 A, ton 100, and CuBe electrodes. Finally, 12 A current, ton 100, and electrode E-Cu were analysed for the lowest Ra value. The results showed a better result in MRR and Ra with increasing discharge current, while a better result was obtained in TWR with increasing pulse duration and decreasing discharge current. In addition, it was observed that the E-Cu electrode performed better than the CuBe electrode in processing TiN-coated Ti6Al4V.

The Significantly Enhanced Mechanical and Tribological Performances of the Dual Plasma Nitrided and PVD Coated Ti6Al4V Alloy

The Significantly Enhanced Mechanical and Tribological Performances of the Dual Plasma Nitrided and PVD Coated Ti6Al4V Alloy

High temperature oxidation behavior of thermal and plasma processed aluminide coated Ti6Al4V alloys

In this study, the high temperature cyclic oxidation behavior of thermal and plasma-treated aluminide coated Ti6Al4V alloy was investigated at 800 °C up to 360 h in 24 h cyclic exposures. The microstructural characteristics, phase analysis, morphological features, and microhardness of resultant oxidized samples were evaluated and compared with those of untreated Ti6Al4V alloy. The weight gain studies conducted from the cyclic oxidation tests revealed very minimal weight gain in plasma treated (PT) aluminide coated samples as compared to the thermal treated (TT) and uncoated (UC) samples. XRD results indicate that the UC samples oxidized at 800 °C exhibits the formation of a thick oxide layer consisting of only the rutile phase (TiO2). The TT and PT samples oxidized at 800 °C revealed presence of both alumina (Al2O3) and rutile (TiO2) phases. However, PT samples revealed stable α-Al2O3 phase whereas the TT samples showed metastable θ-Al2O3 phases in the oxide layer. The surface morphological features reveal that the oxide film formed on the surface of the PT samples had enough stability at 800 °C irrespective of the oxidation time. The PT samples exhibited higher hardness and improved oxidation resistance as compared to TT and UC samples. Increase in thermal stability, mechanical and oxidation properties of PT samples could be attributed to the formation of stable alumina (α-Al2O3) and presence of nanocrystalline aluminide phases (TiAl3 & TiAl2) in the diffusion layers during the oxidation tests. Therefore, a strong emphasis was placed on correlating the interfacial processes to the high temperature oxidation behavior.

Role of phosphate, silicate and aluminate in the electrolytes on PEO coating formation and properties of coated Ti6Al4V alloy

A comparison of PEO layers on Ti6Al4V alloy formed in phosphate, aluminate and silicate-based electrolytes respectively, has been made to reveal the influence of the electrolyte composition on the formation process. The phosphate-based electrolyte has been identified as the most promising one as it has the best coating formation efficiency and the lowest breakdown voltage. On the bases of the microstructure and elemental/phase analysis of the different PEO coatings, it could be observed that the PEO coating formed in phosphate-based electrolyte is mainly composed of anatase and rutile. An amorphous phase is dominant in the coating produced in silicate-based electrolyte. Moreover, there are mainly γ-Al2O3, Na2Al2xO3x+1 and TiAl2O5 present in the coating formed in the aluminate-based electrolyte. The coating formation process in silicate- and aluminate-based electrolytes is more dependent on the deposition originating from the electrolytes. All of the coatings have shown noticeable corrosion resistance and good performance in the photocatalytic test as the degradation rates of methyl orange higher than 45 %. Thus, multifunctional PEO coatings on Ti6Al4V alloy are obtained.

Mechanical and chemical properties of CoCrFeNiMo0.2 high entropy alloy coating fabricated on Ti6Al4V by laser cladding

CoCrFeNiMo0.2 high entropy alloy (HEA) coating was successfully synthesized on Ti6Al4V sheet by laser cladding. Microstructural characteristics of the HEA coating were investigated by the combined use of multiple characterization techniques. The results indicate that the coating consists of body-centered cubic (BCC) and σ phases with a typical uniform dendrite microstructure. The hardness of the coating is ∼900 HV0.1, about 2.3 times that of the substrate. The coated Ti6Al4V alloy presents better oxidation resistance than Ti6Al4V at 600 °C due to a compact oxide layer rich in Cr element. Compared to the Ti6Al4V substrate, a lower wear rate is noted for the coating, demonstrating greatly improved wear resistance, especially at 600 °C. The wear mechanisms of the coating are dominated by abrasive wear and oxidative wear. A more positive corrosion potential value and lower corrosion current density value are found for the coating, indicating a better corrosion resistance than the Ti6Al4V alloy. In-depth analyses suggest that the improved surface performance is associated with combined contributions from the solid-solution strengthening and grain refinement hardening, as well as the addition of Cr element.

Evaluation of fluorohydroxyapatite/strontium coating on titanium implants fabricated by hydrothermal treatment.

Titanium and its alloys are considered as appropriate replacements for the irreparable bone. Calcium phosphate coatings are widely used to improve the osteoinduction and osseointegration ability of titanium alloys. To further improve the performance of the calcium phosphate-coated implants, strontium (Sr) was introduced to partially replace the calcium ions. In this study, the effect of Sr ion addition on the fluorohydroxyapatite (FHA)-coated Ti6Al4V alloy was investigated and all the coatings were treated under hydrothermal condition. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the phases and microstructures, respectively. Shear tests were done to evaluate the bond strength of the coating layer. MTT, adhesion, and alkaline phosphatase tests were performed to evaluate the biocompatibility and osteogenic behavior of the samples. Results showed that the average crystallite size for the strontium-doped FHA samples was 48nm and the bond strength had increased 13.15% in comparison with FHA-coated samples. Analysis of variance showed p value for all MTT tests at more than 0.322 and there was not any evidence of cell death after 7days. The results of the ALP test showed that the increase of the cell activity in Sr samples from day 7 to 14 is three times higher than the FHA ones.

Electrochemical, Tribological and Biocompatible Performance of Electron Beam Modified and Coated Ti6Al4V Alloy

Vacuum cathodic arc TiN coatings with overlaying TiO2 film were deposited on polished and surface roughened by electron beam modification (EBM) Ti6Al4V alloy. The substrate microtopography consisted of long grooves formed by the liner scan of the electron beam with appropriate frequencies (500 (AR500) and 850 (AR850) Hz). EBM transformed the α + β Ti6Al4V mixed structure into a single α’-martensite phase. Тhe gradient TiN/TiO2 films deposited on mechanically polished (AR) and EBM (AR500 and AR850) alloys share the same surface chemistry and composition (almost stoichiometric TiN, anatase and rutile in different ratios) but exhibit different topographies (Sa equal to approximately 0.62, 1.73, and 1.08 μm, respectively) over areas of 50 × 50 μm. Although the nanohardness of the coatings on AR500 and AR850 alloy (approximately 10.45 and 9.02 GPa, respectively) was lower than that measured on the film deposited on AR alloy (about 13.05 GPa), the hybrid surface treatment offered improvement in critical adhesive loads, coefficient of friction, and wear-resistance of the surface. In phosphate buffer saline, all coated samples showed low corrosion potentials and passivation current densities, confirming their good corrosion protection. The coated EBM samples cultured with human osteoblast-like MG63 cells demonstrated increased cell attachment, viability, and bone mineralization activity especially for the AR500-coated alloy, compared to uncoated polished alloy. The results underline the synergetic effect between the sub-micron structure and composition of TiN/TiO2 coating and microarchitecture obtained by EBM.

Surface modification of nanocomposite Al2O3/Gr/HAP coating for improving wear and corrosion behaviour on Ti–6Al–4V alloy using sol–gel technique

In this work, Alumina/Graphene/Hydroxyapatite as a nanocomposites developed using sol–gel associated Dip coating technique on Ti–6Al–4V Substrates. The wear and corrosion behaviour is a predominant factor for implant material like Ti–6Al–4V alloys that reduces the function and service life of the components. The tribological behaviour of Al2O3/Gr/HAP-coated and -uncoated substrates was investigated by wear test using pin-on-disk tribometer. The corrosion resistance of coated and uncoated substrate was analyzed by potentiodynamic polarization studies in SBF solution at 37 °C. In addition, the performance of the coated surface was assessed by X-ray Diffraction analysis (XRD), scanning electron microscopy (SEM), Atomic Force Microscopy (AFM), and Raman Spectroscopy. The lower wear rate is attributed to the hardness and it was observed that the hardness value increased from 358 to 616 HV, respectively. This study resulted that the surface-coating technique can efficiently improve the wear and corrosion resistance of coated Ti–6Al–4V alloys.

Characterization of SiO2 sol-gel coated Ti6Al4V alloy obtained by using TEOS and GPTMS

Synthesis of silicon oxide (SiO2) via the sol-gel method and SiO2 coating ability on to Ti6Al4V alloy were investigated, in the novel study. Ti6Al4V alloy is the most used alloy in biomedical applications due to its many advantages. However, it has a minor disadvantage like releasing ions into the human body. In this study, the substrate material Ti6Al4V alloy samples were coated using the sol-gel method with alkoxysilane solutions (tetraethyl orthosilicate, TEOS; Si(OC2H5)4 and glycidoxypropyltrimethoxysilane, GPTMS; C9H20O5Si) containing the unit of prepared Si(OR)n after the surface preparations were made. The prepared solutions were examined using thermal analysis methods and the process temperatures to be applied to the coatings were determined according to the results of the analysis. Coated samples were subjected to aging, drying, and sintering processes at specified temperatures. The morphologies and structures of the samples were investigated by using a scanning electron microscope with energy-dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The sol-gel coating ability of the silicon oxide on the surface of the Ti6Al4V alloys has been discussed. The results demonstrate that cracks were observed in coating produced by TEOS precursor whereas the coatings used GPTMS precursor exhibited crack-free surface independently of dipping number. The crack formation tended to reduce with increasing dipping number of coatings produced by TEOS precursor. Distances between coating islets gradually became smaller as the number of dippings increased, and the continuity of the coatings increased. It has been observed that SiO2 coating layers produced with GPTMS are obtained in a more continuous and crack-free form than the layers produced with TEOS.

The Effect of Oxalic Acid on Corrosion Resistance of Hydroxyapatite Sol-Gel Coated Ti6Al4V Alloys

Bu çalışmada biyomalzeme uygulamalarında kullanılmak üzere etkili bir biyomalzeme geliştirilmesi amaçlanmış ve sol-jel yöntemi kullanılarak Ti6Al4V altlık malzemeler üzerine hidroksiapatit kaplamalar yapılmıştır. Sol-jel yöntemi ile biyoaktifliği ve korozyon dayanımı yüksek, çatlaksız bir kaplama tabakası elde etmek amaçlanmıştır. Bu amaçla, hazırlanan hidroksiapatit çözeltilerine farklı oranlarda oksalik asit (OA, C2H2O4) eklenmiş ve OA’nın kaplama morfolojisinde oluşturduğu değişimler incelenmiştir. Analizlerde, enerji dispersif spektrumlu taramalı elektron mikroskobu (SEM-EDS) ve X-Işını kırınımı (XRD) kullanılmıştır. Kaplama yapılmış numunelerin korozyon özelliklerinde meydana gelen değişimler ise hazırlanan yapay vücut sıvısı içinde üç elektrotlu sistem kullanılarak gerçekleştirilen elektrokimyasal-potansiyodinamik korozyon testleri ile incelenmiştir. Çalışmanın sonucunda OA katkı oranının artması ile kaplama adacıkları arasındaki mesafelerin kapandığı, morfolojide gözlemlenen çatlakların azaldığı ve büyük ölçüde engellendiği gözlemlenmiştir. Korozyon hızları kıyaslandığında ise OA miktarının ağırlıkça % 0,001 olduğu ve 0,015 olduğu numunelerde korozyon hızının diğer katkılı numunelere göre 10 kat ve katkısız numuneye göre ise 5 kat daha az olduğu gözlemlenmiştir.

Investigation of hot-dip aluminized Ti6Al4V alloy processed by different thermal treatments in an oxidizing atmosphere

Plasma assisted aluminide coating was formed on Ti6Al4V alloy by hot-dip aluminizing (HDA) followed by two-step diffusion heat treatment. The HDA coated Ti6Al4V alloys were subjected to solution annealing (900°C/1h) and aging heat treatment (500°C/6h) by plasma processing route and compared with thermal treatment. The resultant coated and heat-treated samples were characterized using SEM for surface morphology and microstructure analysis, EDS for elemental analysis and x-ray diffraction (XRD) for phase analysis. From the characterization, it was observed that after the diffusion heat treatments, the microstructure of aluminized coating consisted of an outer layer of Al2O3 followed by TiAl3, TiAl2, Ti-Al, and Ti3Al phases. In the diffusion zone, hardness variation in the range of 366–490HV0.05 and 342–525HV0.05 was observed in case of thermal and plasma-treated samples respectively. However, in the diffusion zone, the microhardness of plasma-treated samples was slightly higher than the thermally treated samples. The plasma ion bombardment appears to alter the crystalline size due to vacancy concentration which leads to increment in the hardness value. The details of experiments, characterization along with the interpretations and comparison of various microstructural aspects have been presented in this manuscript.

Mechanical properties and in vitro biocompatibility evaluation of TiN/TiO2 coated Ti6Al4V alloy

Production of a mechanical matched and bioactive bone substitute is important for biomedical application in bone defects repair. In this paper, as-received (AR) and solution treated (ST) Ti6Al4V was coated with PVD deposited TiN/TiO2 films. The microstructure, phase composition, adhesion, and hardness of the bioactive coatings were characterized. Except near stoichiometric (2 0 0) and (2 2 0) textured TiN phase, XRD analysis revealed that the superficial TiO2 consisted of rutile and anatase with ratio 71%-29% and 85%-15% on the surface of AR and ST samples, respectively. With SEM cross-section micrographs it was measured that the thickness of the nitride and oxide was 3.3 and 0.5 μm, respectively. The scratch test showed that the coating deposited on the treated substrate exhibited an ability to higher critical load (72.0 ± 3.16 N) as opposed to that on AR substrate (43.4 ± 1.42 N). The coating deposited on the ST substrate had higher nanohardness and elastic modulus (5.33 GPa and 145.70 GPa, respectively) than that on AR alloy (2.73 GPa and 37.70 GPa, respectively). Cell adhesion, viability, and bone mineralization of osteoblast cells were determined using adsorption, MTT assay, and microscopy. The coated samples displayed better cell attachment and cytocompatibility with no negative effects on MG63 cells. Increased cell viability by almost 100% was seen after 24 h on both coated samples relative to the bare AR alloy. After 31 days, the mineralized areas at coated ST surface were almost twice higher as opposed to the coated AR samples because of the different surface characteristics and oxide composition.

Microstructure, Wettability, Corrosion Resistance and Antibacterial Property of Cu-MTa2O5 Multilayer Composite Coatings with Different Cu Incorporation Contents.

Bacterial infection and toxic metal ions releasing are the challenges in the clinical application of Ti6Al4V alloy implant materials. Copper is a kind of long-acting, broad-spectrum and safe antibacterial element, and Ta2O5 has good corrosion resistance, wear-resistance and biocompatibility, they are considered and chosen as a potential coating candidate for implant surface modification. In this paper, magnetron sputtering technology was used to prepare copper doped Ta2O5 multilayer composite coating Cu-Ta2O5/Ta2O5/Ta2O5-TiO2/TiO2/Ti (Cu-MTa2O5 for short) on Ti6Al4V alloy surface, for studying the effect of copper incorporation on the microstructure, wettability, anticorrosion and antibacterial activities of the composite coating. The results showed that Cu-MTa2O5 coating obviously improves the hydrophobicity, corrosion resistance and antibacterial property of Ti6Al4V alloy. In the coating, both copper and Ta2O5 exhibit an amorphous structure and copper mainly presents as an oxidation state (Cu2O and CuO). With the increase of the doping amount of copper, the grain size, roughness, and hydrophobicity of the modified surface of Ti6Al4V alloy are increased. Electrochemical experiment results demonstrated that the corrosion resistance of Cu-MTa2O5 coated Ti6Al4V alloy slightly decreased with the increase of copper concentration, but this coating still acts strong anticorrosion protection for Ti6Al4V alloy. Moreover, the Cu-MTa2O5 coating can kill more than 97% of Staphylococcus aureus in 24 h, and the antibacterial rate increases with the increase of copper content. Therefore, Cu-MTa2O5 composite coating is a good candidate for improving anticorrosion and antibacterial properties of Ti6Al4V alloy implant medical devices.

The effect of residual stress and gradient nanostructure on the fretting fatigue behavior of plasma electrolytic oxidation coated Ti–6Al–4V alloy

The influence of plasma electrolytic oxidation (PEO) treatment and ultrasonic surface rolling process (USRP) pretreatment followed by PEO treatment on the fretting fatigue (FF) performance of Ti–6Al–4V alloy was investigated. PEO treatment yielded effective improvement in the FF life of the alloy at low stress levels, which was attributed to that the coating with high hardness suppressed crack initiation. The FF life of USRP-PEO-coated specimens was significantly improved and by at least a factor of 81 at a maximum alternating stress of 650 MPa compared to the uncoated ones. This resulted mainly from the fact that the high-hardness coating retarded the FF crack initiation, and the synergistic effect of the induced large deep-distributed compressive residual stress and gradient nanostructure retarded early FF crack propagation. The compressive residual stress played the dominant role in the FF life improvement. For the PEO-coated or USRP-PEO-coated specimens, the FF cracks were initiated at the interface of stick zone and slip zone in the fretting wear contact zone of the coating and then propagated through the coating and coating/substrate interface into the substrate. During fretting, the wear debris of the coating moved into the cracks and promoted early crack propagation as wedge effect.

In vitro and in vivo investigations of a-C/a-C:Ti nanomultilayer coated Ti6Al4V alloy as artificial femoral head

Hydrogen-free a-C/a-C:Ti nanomultilayer (a-C NM) films were deposited on medical Ti6Al4V by the magnetron sputtering technique under bias-graded voltage. Cell tests and implantations were performed for the a-C NM films coated Ti6Al4V with the uncoated Ti6Al4V as the control. The canine total hip arthroplasty (THA) surgeries were conducted for 12 dogs using the coated femoral heads, with the CoCr heads as the control. Results of cell tests showed that the coated Ti6Al4V had no cytotoxicity, and there was no statistical difference of the cell attachment rates between the coated and uncoated sample (P = 0.091). No significant difference of the tissue response around the coated and uncoated implants were observed after the intramuscular (P = 0.679) and intraosseous implantations (P = 0.122). After two years of successful canine THA, the polyethylene wear particles isolated from periprosthetic soft tissue showed similar sizes, shapes and counts in the two groups (all of the P values >0.05). The retrieved femoral heads showed slightly change of the surface roughness, but no statistical differences between groups (P = 0.696). However, the systemic metal ion analysis indicated that the content of Co and Cr ions released in the coated group (Co: 0.71 ± 0.06 μg/L, Cr: 0.52 ± 0.05 μg/L) were significant lower than that in the control (Co: 1.98 ± 0.16 μg/L, Cr: 1.17 ± 0.19 μg/L) (both P < 0.005). Histological analysis of the periprosthetic tissue in CoCr group showed a severer histiocyte response than that in the coated group (P = 0.029). The head-taper interfaces showed galvanic corrosion attack in the CoCr group, but not in the coated Ti6Al4V group. Therefore, the a-C NM films coated Ti6Al4V exhibited good biocompatibility as an implant material. Compared with the CoCr, the coated Ti6Al4V femoral head could provide comparable in vivo wear properties, release less harmful metal ions and reduce the inflammatory response in periprosthetic tissue, which may help to prolong the longevity of prostheses.