In vitro studies of plasma-sprayed hydroxyapatite/Ti-6Al-4V composite coatings in simulated body fluid (SBF)

The bioactivity of plasma-sprayed hydroxyapatite (HA)/Ti-6Al-4V composite coatings was studied by soaking the coatings in simulated body fluid (SBF) for up to 8 weeks. This investigation was aimed at elucidating the biological behaviour of plasma-sprayed HA/Ti-6Al-4V composite coatings by analyzing the changes in chemistry, and crystallinity of the composite coating in a body-analogous solution. Phase composition, microstructure and calcium ion concentration were analyzed before, and after immersion. The mechanical properties, such as tensile bond strength, microhardness and Young's modulus were appropriately measured. Results demonstrated that the tensile bond strength of the composite coating was significantly higher than that of pure HA coatings even after soaking in the SBF solution over an 8-weeks period. Dissolution of Ca-P phases in SBF was evident after 24h of soaking, and, a layer of carbonate-apatite covered the coating surface after 2 weeks of immersion. The mechanical properties were found to diminish with soaking duration. However, slight variation in mechanical properties was found after supersaturation of the calcium ions was attained with the precipitation of the calcium phosphate layers.     

Activity of plasma sprayed yttria stabilized zirconia reinforced hydroxyapatite/Ti-6Al-4V composite coatings in simulated body fluid

Hydroxyapatite (HA)/yttria stabilized zirconia/Ti-6Al-4V bio-composite coatings deposited onto Ti-6Al-4V substrate through a plasma spray technique were immersed in simulated body fluid (SBF) to investigate their behavior in vitro. Surface morphologies and structural changes in the coatings were analyzed by scanning electron microscopy, thin-film X-ray diffractometer, and X-ray photoelectron spectroscopy. The tensile bond strength of the coatings after immersion was also conducted through the ASTM C-633 standard for thermal sprayed coatings. Results showed that carbonate-containing hydroxyapatite (CHA) layer formed on the surface of composite coatings after 4 weeks immersion in SBF solution, indicating the composite coating possessed excellent bioactivity. The mechanical properties were found to decrease with immersion duration of maximum 56 days. However, minimal variation in mechanical properties was found subsequent to achieving supersaturation of the calcium ions, which was attained with the precipitation of the calcium phosphate layers. The mechanical properties of the composite coating were found to be significantly higher than those of pure HA coatings even after immersion in the SBF solution, indicating the enhanced mechanical properties of the composite coatings.     

TEM and STEM analysis on heat-treated and in vitro plasma-sprayed hydroxyapatite/Ti-6Al-4V composite coatings

A cogent understanding of the microstructure, and indeed nano-structure, of hydroxyapatite (HA) and the interface between Ti-6Al-4V and HA is crucial to its appropriateness as a biomaterials. This paper reports the analysis of plasma-sprayed HA/Ti-6Al-4V composites by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) to elucidate the intricate nature of the materials following plasma spray processing and in vitro evaluation. The novel Ti-6Al-4V/HA composite coating, with approximately 48 wt% HA, had demonstrated attractive tensile adhesion strength (approximately 28 MPa) and improved Young's modulus (approximately 55 GPa). Experimental results demonstrated that amorphous calcium phosphate and fine HA grains were formed during rapid splat solidification in the as-sprayed composite coatings. Small Ti-6Al-4V grains were observed adjacent to the amorphous calcium phosphate. The coatings were further heat treated at 600 degrees C for 6 h, and significant crystallisation of the amorphous calcium phosphate phase took place. However, complete crystallisation was not achieved at this temperature, as the coatings invariably contained a small amount of amorphous calcium phosphate phase in some local regions. After immersion in simulated body fluid for 2 weeks and 10 weeks, TEM and STEM confirmed that the interfaces inside the coating maintained good microstructural integrity.     

An in vitro investigation of plasma sprayed hydroxyapatite (HA) coatings produced with flame-spheroidized feedstock.

The in vitro behaviour and characteristics of plasma sprayed hydroxyapatite (HA) coatings using flame-spheroidized HA feedstock powder on titanium alloy (Ti-6Al-4V) substrates were investigated in a simulated physiological environment as an attempt to reflect the actual incubational condition of an implant in a human body system. As-sprayed and heat-treated HA coatings were immersed in a simulated body fluid with ionic concentrations comparable to that of human blood plasma for time intervals 2, 4, 6, 8 and 10 weeks. Rapid dissolution of calcium phosphate was found to occur within the first 4 weeks, and after the 5th week a retarding rate of 4.1 mM week(-1) was observed where precipitation, nucleation, and, growth of a carbonate-containing, poorly crystallized or amorphous calcium phosphate layer on the as-sprayed coatings were noted. The heat-treated coatings showed minimal or no precipitation on the surface except for the presence of calcite minerals that is due to carbonation effect. Complete dissolution of other calcium phosphate phases such as tetracalcium phosphate, tricalcium phosphate and calcium oxide was also noted after 2 weeks of immersion due to higher ionic solubility relative to HA. A declining trend in respective microhardness and elastic modulus of the as-sprayed HA coatings from 207.06 +/- 3.2 H(k300) to 131.8 +/- 5.2 H(k300) and from 31.37 +/- 1.4 to 19.81 +/- 1.6 GPa was observed after 10 weeks of immersion. Tensile bond strength of both types of coatings showed similar declining trend, with an average dip from 24.5 +/- 2.4 to 7.9 +/- 2.6 MPa. Nevertheless. the heat-treated samples showed rather reasonable mechanical stability and structural integrity of 26.7 +/-1.4 GPa in elastic modulus after soaking.     

Immersion behavior of RF magnetron-assisted sputtered hydroxyapatite/titanium coatings in simulated body fluid.

The focus of the present study was on the dissolution/degradation behavior of a series of magnetron-sputtered, single-layered HA/Ti coatings on Ti-6Al-4V substrate immersed in SBF. Changes in coating morphology, crystal structure, and adhesion strength with immersion time are characterized. XRD, FTIR, and LVSEM results consistently indicate that highly crystalline monolithic HA coating is very dissolvable in SBF. The monolithic HA coating is largely delaminated in 3 weeks and entirely peeled off the substrate in 7 weeks. The dissolution is even greater for 95HA/5Ti coating, which severely disintegrated in only 1 week. The amorphous-like coatings sputtered from targets comprising 10 vol % or more Ti, however, appeared almost intact, and their adhesion strengths, which were all higher than 60 MPa, did not change much (within 10%) even after 14 weeks of immersion. The coatings from targets comprising roughly 10-50 vol % Ti combine advantages of high and nondeclining adhesion strength, high resistance to SBF attack, and possibly much higher bioactivity (with large amounts of Ca, P, etc., dissolved in the coatings) than that of Ti.     

Processing of HA-coated Ti-6Al-4V by a ceramic slurry approach: an in vitro study

Hydroxyapatite-coated titanium alloy composite powders (Ti-6Al-4V/HA) was produced by a ceramic slurry approach. The aim was to evaluate the stability of the coating when subjected to a physiological medium simulated body fluid (SBF). Three consolidation conditions (700 degrees C for 5 h, 700 degrees C for 8 h and 700 degrees C for 11 h) were used in the production of the Ti-6Al-4V/HA composite powders. Results showed that biodissolution followed by apatite precipitation had taken place after soaking in SBF. In addition, it was found that consolidation at 700 degrees C for 5 h resulted in a weak mechanical locking of calcium phosphate on the Ti-6Al-4V surfaces; and the formation of small crystallites, which would increase the dissolution rate.     

Porous Ti-6Al-4V alloy fabricated by spark plasma sintering for biomimetic surface modification

Porous compacts with both biological and biomechanical compatibilities and high strength were developed. Spherical powders of Ti-6Al-4V alloy, which were either as received or surface modified with the use of calcium ions by hydrothermal treatment (HTT), were fabricated by a spark plasma sintering process. The porous compacts of pure Ti were used as reference materials. Porosity was approximately 30%, and compressive strengths were 113 and 125 MPa for the as-received Ti alloy powders and those modified by the HTT process, respectively. The bending strength and elastic modulus of as-received Ti alloy powders were 128-178 MPa and 16-18 GPa, respectively. Each of the compacts was immersed in simulated body fluid (SBF). The amount of adsorption/precipitation of calcium phosphate through the compacts was measured by weight change and was observed by SEM. The compacts were covered with calcium phosphate after 2 weeks of immersion in SBF. The compacts of Ti alloy had plenty of precipitated apatite crystals, and modification by HTT accumulated more precipitation. Because calcium phosphate is a mineral component of bone, apatite, which is precipitated on the surface of the compacts, could adsorb proteins and/or drugs such as antibiotics. It is expected that a large amount of proteins and/or drugs could be impregnated when the porous compacts developed are used.     

Microstructures and mechanical properties of powder injection molded Ti-6Al-4V/HA powder

Taguchi method with an L9 orthogonal array was employed to investigate the sintered properties of Ti-6Al-4V/HA tensile bars produced by powder injection molding. The effects of sintering factors at the 90% significance level: sintering temperature (1050 degrees C, 1100 degrees C and 1150 degrees C), heating rate (5 degrees C/min, 7.5 degrees C/min and 10 degrees C/min), holding time (30, 45 and 60 min) and cooling rate (5 degrees C/min, 20 degrees C/min and 40 degrees C/min) were investigated. Results showed that sintering temperature, heating rate and cooling rate have significant effects on sintered properties, whereas the influence of holding time was insignificant. It was found that a sintering temperature of 1100 degrees C, a heating rate of 7.5 degrees C/min and a cooling rate of 5 degrees C/min increased the relative density, Vicker's microhardness, flexural strength and flexural modulus. However, a further increment of sintering temperature to 1150 degrees C did not show any discernable improvement in the relative density and Vicker's microhardness, but there was a slight increase of 0.6% and 0.9% in the flexural strength and flexural modulus, respectively. Mechanically strong Ti-6Al-4V/HA parts with an open porosity of around 50% were developed.     

Novel production method and in-vitro cell compatibility of porous Ti-6Al-4V alloy disk for hard tissue engineering

Porous metals are attractive due to its unique physical, mechanical, and new bone tissue ingrowth properties. In the present study, the production of highly porous Ti-6Al-4V parts by powder metallurgical technology and subsequently it's uses in in vitro bone tissue engineering is described. A space-holder method using carbamide with different particle size to produce parts with porosities between 35 and 70% were applied. The compressive strength and Young's modulus of porous Ti-6Al-4V were determined. Results indicated that stress and Young's modulus decrease with increasing porosity and pore size. The porous parts are characterized by scanning electron microscopy. Furthermore, study was to investigate the effects of three different porosities of porous Ti-6Al-4V (35, 50, and 70%) on proliferation, differentiation, and cell-matrix interaction of mouse osteoblast-like cells, MC-3T3. Results showed that the cell proliferation was significantly (p < 0.05) higher on 70% porous Ti-6Al-4V. However, synthesis of different types of extra cellular matrix proteins was also more abundant on 70% porous Ti-6Al-4V than 35 and 50% porous Ti-6Al-4V disk except some specific proteins. An increase in alkaline phosphate activity was significantly (p < 0.05) higher on 70 and 50% porous Ti-6Al-4V disk after 12 days of MC-3T3 cells incubation. Above all, results indicated that porosity (nearly 70%) of porous Ti-6Al-4V topography affects proliferation and differentiation of osteoblast-like MC-3T3 cells. The results showed that this novel process is a promise to fabricate porous biomaterials for bone implants.     

Mechanical properties of calcium phosphate scaffolds fabricated by robocasting

The mechanical behavior under compressive stresses of beta-tricalcium phosphate (beta-TCP) and hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) technique is analyzed. Concentrated colloidal inks prepared from beta-TCP and HA commercial powders were used to fabricate porous structures consisting of a 3-D tetragonal mesh of interpenetrating ceramic rods. The compressive strength and elastic modulus of these model scaffolds were determined by uniaxial testing to compare the relative performance of the selected materials. The effect of a 3-week immersion in simulated body fluid (SBF) on the strength of the scaffolds was also analyzed. The results are compared with those reported in the literature for calcium phosphate scaffolds and human bone. The robocast calcium phosphate scaffolds were found to exhibit excellent mechanical performances in terms of strength, especially the HA structures after SBF immersion, indicating a great potential of this type of scaffolds for use in load-bearing bone tissue engineering applications.     

Structure and immersion behavior of plasma-sprayed apatite-matrix coatings

The microstructure and properties of a series of plasma-sprayed coatings from sinter-granulated powders fabricated from SiO2, CaO, P2O5 and Na2O-containing HA composite powders on Ti-6Al-4V substrate were reported. The immersion behavior of these coatings in a simulated body fluid (SBF) was also investigated. The results showed that sinter-granulated apatite-matrix powders were irregularly shaped and appeared quite similar. XRD patterns showed that during fabrication of the powders, P2O5 and SiO2 enhanced the decomposition of HA structure, while CaO and Na2O did not. Reasonably high bond strengths (45-50 MPa) were obtained from all coatings. The plasma spray process itself enhanced the decomposition of apatite and chemical reactions among different phases. When immersed in SBF, the intensities of such phases as alpha- and beta-TCP in all coatings decreased with immersion time and an apatite precipitation took place on all coating surfaces. The immersed SiO2- and CaO-containing HA (HSC) coating had the highest rate of apatite precipitation among all coatings. The variations in calcium ion concentration in simulated body fluid indicated that the HSC-immersed solution reached its maximal Ca concentration the earliest, while the HSCP (HA, SiO2, CaO and P2O5)-immersed solution reached its maximum the latest.     

Microstructure and mechanical properties of plasma sprayed HA/YSZ/Ti-6Al-4V composite coatings

Plasma sprayed hydroxyapatite (HA) coatings on titanium alloy substrate have been used extensively due to their excellent biocompatibility and osteoconductivity. However, the erratic bond strength between HA and Ti alloy has raised concern over the long-term reliability of the implant. In this paper, HA/yttria stabilized zirconia (YSZ)/Ti-6Al-4V composite coatings that possess superior mechanical properties to conventional plasma sprayed HA coatings were developed. Ti-6Al-4V powders coated with fine YSZ and HA particles were prepared through a unique ceramic slurry mixing method. The so-formed composite powder was employed as feedstock for plasma spraying of the HA/YSZ/Ti-6Al-4V coatings. The influence of net plasma energy, plasma spray standoff distance, and post-spray heat treatment on microstructure, phase composition and mechanical properties were investigated. Results showed that coatings prepared with the optimum plasma sprayed condition showed a well-defined splat structure. HA/YSZ/Ti-6Al-4V solid solution was formed during plasma spraying which was beneficial for the improvement of mechanical properties. There was no evidence of Ti oxidation from the successful processing of YSZ and HA coated Ti-6Al-4V composite powders. Small amount of CaO apart from HA, ZrO(2) and Ti was present in the composite coatings. The microhardness, Young's modulus, fracture toughness, and bond strength increased significantly with the addition of YSZ. Post-spray heat treatment at 600 degrees C and 700 degrees C for up to 12h was found to further improve the mechanical properties of coatings. After the post-spray heat treatment, 17.6% increment in Young's modulus (E) and 16.3% increment in Vicker's hardness were achieved. The strengthening mechanisms of HA/YSZ/Ti-6Al-4V composite coatings were related to the dispersion strengthening by homogeneous distribution of YSZ particles in the matrix, the good mechanical properties of Ti-6Al-4V and the formation of solid solution among HA, Ti alloy and YSZ components.     

Early apatite deposition and osteoblast growth on plasma-sprayed dicalcium silicate coating

Dicalcium silicate coating was deposited onto a Ti-6Al-4V substrate using plasma-spraying technology. The coating was immersed in simulated body fluid (SBF) for 1, 3, 6, 12, 24, and 48 h to investigate early apatite formation on the coating. Osteoblasts were also seeded onto the surface of the dicalcium silicate coating to evaluate its biocompatibility. Cold field-emission scanning electron microscopy and energy-dispersive X-ray spectrometry were used to evaluate the morphologies and determine the chemical composition of the coatings. The surface structural changes caused by immersion in SBF were analyzed using thin-film X-ray diffraction. After the dicalcium silicate coating was soaked in SBF solution 1-6 h, two types of particles containing calcium and phosphorus were formed on the surface. One type consisted of relatively larger particles (P1) precipitated on the surface of the coating from the precursor cluster formed in the SBF solution. The second type was composed of particles (P2) nucleated on the surface of the coating. With increasing immersion time, the particles coalesced to form a surface Ca-P layer. The Ca-P layer was composed of amorphous calcium phosphate that was not transformed to crystalline apatite until the immersion time in SBF exceeded 24 h. The formation mechanism of the Ca-P layer and apatite on the surface of the coating is believed to be involved in the formation of the Si 3-ring active surface site with negative charge. The cell-seeding test revealed that osteoblasts grew and proliferated very well on the surface of the dicalcium silicate coating.     

Mechanical properties of calcium phosphate coatings deposited by laser ablation

Amorphous calcium phosphate and crystalline hydroxyapatite coatings with different morphologies were deposited onto Ti-6Al-4V substrates by means of the laser ablation technique. The strength of adhesion of the coatings to the substrate and their mode of fracture were evaluated through the scratch test technique and scanning electron microscopy. The effect of wet immersion on the adhesion was also assessed. The mechanisms of failure and the critical load of delamination differ significantly depending on the phase and structure of the coatings. The HA coatings with granular morphology have higher resistance to delamination as compared to HA coatings with columnar morphology. This fact has been related to the absence of stresses for the granular morphology.     

Interaction of a plasma-sprayed hydroxyapatite coating in contact with human osteoblasts and culture medium.

The loss of calcium from plasma-sprayed calcium phosphate ceramics (CPCs) on bioinert metal substrate (Ti-6Al-4V) immersed in cell culture medium with or without human osteoblast culture was measured. The ceramics were a CPC and a duplex system composed of a CPC layer on an alumina coating. The dissolution of calcium compounds was monitored by measuring the calcium leaked from the coatings into the culture medium in 15 days. Calcium was measured by flame photometry. The surfaces of the ceramics exposed to the culture medium and in contact with osteoblasts were analysed by X-ray diffraction (XRD). The dissolution process occurred in the first 6 days of contact, but the calcium released into the culture medium was only a small fraction of the calcium content of the coatings. The presence or absence of osteoblasts on the surface of the ceramics did not make significant difference for the calcium release. The XRD spectra of the ceramics before and after immersion and in contact with cells did not show a significant change in the compounds of the coatings.     

In vitro behavior of HVOF sprayed calcium phosphate splats and coatings

Hydroxyapatite (HA) coatings and splats deposited by high velocity oxy-fuel (HVOF) spray technique was investigated in vitro. HA coatings prepared from two different HA powder size range (30+/-5 and 50 +/-5 microm) were immersed in a simulated body fluid with various incubation periods of maximum 6 weeks. The dissolution/precipitation behavior was studied and the degradation of HA coatings caused by in vitro ageing was demonstrated by measuring the changes in flexural modulus through a 3-point bend test. It was found that the dissolution and precipitation behavior of the coatings was significantly dependent upon the incipient coating phase composition and the precipitation of bone-like hydroxyapatite on the coating's surface was found to be directly related to the dissolution process. Higher dissolution rates of tricalcium phosphate, tetracalcium phosphate and amorphous calcium phosphate relative to HA, resulted in accelerated precipitation. Furthermore, analysis of coatings' surface morphology demonstrated that advanced precipitation invariably occurred at regions where dissolution took place. Results showed that the changes in flexural modulus of investigated HA coatings accompanying different incubation duration was not systematic but was found to be dependent upon changes of coating structure and other factors brought about by in vitro ageing. In vitro investigation of individual HA splats collected from different HA particle sizes revealed, after 3 days ageing, that the rate ratio of precipitation to dissolution was directly determined by the local phase composition, and this phenomenon could be effectively used to explain the behavior of thermally sprayed HA coatings in vitro. It implied that the precipitation was strongly dependent on the first molecule attachment. To achieve rapid precipitation in vitro, partial molten state of HA particles during HVOF coating deposition was recommended.     

植入用Ti-6Al-4V合金模拟体液浸泡后高频和超高周疲劳性能

目的为预测植入用Ti-6Al-4V钛合金的使用寿命,研究其在模拟体液浸泡后,107周次以后的超高周疲劳性能。方法将Ti-6Al-4V钛合金试样在模拟体液中分别浸泡2 d和6 d;利用超声疲劳实验技术,在室温下分别对这两组试样进行超高周疲劳性能测试;利用电子显微镜观察疲劳断口并对裂纹源进行X射线能谱分析,研究其裂纹萌生机理,并与未经浸泡的同种材料的超声疲劳性能进行对比分析。结果模拟体液浸泡后的材料的S-N曲线与未经浸泡时的趋势相近,在104～108周次范围内的疲劳寿命都呈连续下降状态,在107～108周次循环范围内曲线下降趋势有所变慢;模拟体液浸泡后的试样在107周次之前寿命下降更快,107周次之后模拟体液浸泡过的试样寿命比未处理的试样寿命低;浸泡6 d后的试样的寿命和浸泡2 d后的相差不大。疲劳循环超过107周次后,仍然发生疲劳断裂,并不存在传统意义上的疲劳极限。疲劳寿命108周次以后的试样疲劳裂纹在内部萌生,一般为铝元素聚集区;疲劳寿命107周次以前裂纹一般萌生于试件表面,有些试件出现了多处裂纹源。结论模拟体液浸泡会降低Ti-6Al-4V钛合金的超高周疲劳性能;随着循环周次的增加,裂纹萌生由试件表面向其内部转换。     

Poly(D,L-lactic acid) coated 45S5 Bioglass-based scaffolds: processing and characterization

A comparative investigation has been carried out on the mechanical properties and bioactivity of Bioglass-based foams, before and after applying a poly(D,L-lactic acid) (PDLLA) coating layer on the foam struts. It was found that the bioactivity of foams upon immersion in simulated body fluid (SBF) was maintained in the PDLLA-coated foams; however, the transformation kinetics in SBF of the crystalline phase (Na(2)Ca(2)Si(3)O(9)) in the foam struts to an amorphous calcium phosphate phase was retarded by PDLLA coating. The compressive and three-point bending strengths of the Bioglass-based foams were slightly improved by the PDLLA-coating, and the work-of-fracture of the foams was considerably enhanced, as indicated by stress-strain curves. Immersion in SBF for 4 weeks led to a large decrease of the mechanical strength of as-sintered foams decreased (from 0.3 to 0.03 MPa), because of the transformation of the crystalline phase to an amorphous calcium phosphate. On the other hand, the mechanical strength was well-maintained in PDLLA-coated foams after immersion in SBF for 8 weeks. This behavior was attributed to the in-situ formation of a nanocomposite PDLLA/calcium phosphate film on the strut surfaces upon immersion in SBF.     

Bone growth on and resorption of calcium phosphate coatings obtained by pulsed laser deposition

Three different calcium phosphate coatings of crystalline hydroxyapatite (HA), alpha- and beta-tricalcium phosphate (alpha+beta-TCP), or amorphous calcium phosphate (ACP) obtained by pulsed laser deposition on Ti-6Al-4V were incubated in a potentially osteogenic primary cell culture (rat bone marrow) in order to evaluate the amount and mode of mineralized bone matrix formation after 2 weeks with special emphasis on the type of interfacial structure that was created. Evaluation techniques included fluorescence labeling and scanning electron microscopy. The resistance to cellular resorption by osteoclasts was also studied. Bone matrix delaminated from the ACP coatings, while it remained on the HA and the alpha+beta-TCP coatings even after fracturing. A cementlike line was seen as the immediate contiguous interface with the nondegrading dense HA surface and with the surface of the remaining porous beta-TCP coating. Highly dense and crystalline HA coatings do not dissolve but are capable of establishing a strong bond with the bone matrix grown on top. Chemical and mechanical bonding were considered in this case. Cellular resorption was practically not observed on the HA coatings, but it was observed on the alpha+beta-TCP coatings. Resorption took place as dissolution that was due to the acidic microenvironment.     

Bond strength of plasma-sprayed hydroxyapatite/Ti composite coatings

One of the most important clinical applications of hydroxyapatite (HA) is as a coating on metal implants, especially plasma-sprayed HA coating applied on Ti alloy substrate. However, the poor bonding strength between HA and Ti alloy has been of concern to orthopedists. In this paper, an attempt has been made to enhance the bonding strength of HA coating by forming a composite coating with Ti. The bioactivity of the coating has also been studied. HA/Ti composite coatings were prepared via atmospheric plasma spraying on Ti-6Al-4V alloy substrates. The bond strength evaluation of HA/Ti composite coatings was performed according to ASTM C-633 test method. X-ray diffractometer and scanning electron microscopy were applied to identify the phases and the morphologies of the coatings. The bioactivity of HA/Ti composite coating was qualified by immersion of coating in simulated body fluid (SBF). The obtained results revealed that the addition of Ti to HA improved the bonding strength of coating significantly. In the SBF test, the coating surface was covered by carbonate-apatite, which was testified by X-ray photoelectron spectroscope, indicating good bioactivity for HA/Ti composite coating. The bioactivity of the coating has not been reduced by the addition of Ti.