Ti-6Al-4V钛合金脉冲阳极氧化工艺

研究了Ti-6Al-4V钛合金脉冲阳极氧化工艺,并对影响阳极氧化膜厚度的主要因素(如温度、电流密度、时间等)进行了研究,得到了满足膜厚要求的工艺参数。将优化得出的工艺参数应用于零件的仿形试件生产,得到厚度均匀的阳极氧化膜,并对其表面形貌、成分等进行了分析。     

Effect of transition layer on the performance of hydroxyapatite/titanium nitride coating developed on Ti-6Al-4V alloy by magnetron sputtering

A gradient transition multilayer hydroxyapatite/titanium nitride (HA/TiN) coating was prepared on the Ti-6Al-4V alloy by magnetron sputtering. The composition, surface topography, microstructure, adhesion strength and electrochemical properties of the as-deposited coatings were characterized by SEM/EDS, AFM, XRD, FT-IR and electrochemical workstation. The experimental results showed that the single TiN coating deposited at a partial pressure of nitrogen (N₂) of 0.08?Pa had the best internal stress and tribological performance, and its volume loss was only 0.89% of that of Ti-6Al-4V alloy. The introduction of the TiN transition layer greatly improved the wear resistance of the Ti-6Al-4V alloy, and the adhesion strength of the HA layer to the substrate increased from 6.50?±?0.5?N to 11.70?±?1.2?N, an increase of 56%. The HA/TiN coating surface consisted of uniform hemispherical particles with dense structure and invisible defects (micro-cracks and pores). For the HA surface layer, the crystal structure and active hydroxyl (-OH) group was restored after heat treatment. Potentiodynamic polarization experiments indicated that the HA/TiN coating achieved the lowest corrosion current density and the most positive corrosion potential compared to the single TiN layer and Ti-6Al-4V alloy. In summary, it can be conclude that the gradient transition layer can well improve the mechanical properties and electrochemical behavior of the titanium alloy, and largely ensuring the stability of the surface bioactive coating.     

The influence of chloride and sulphate ions on the corrosion behavior of Ti and Ti-6Al-4V alloy in oxalic acid

The electrochemical behavior of pure Ti and Ti-6Al-4V alloy was investigated in oxalic acid solution using various electrochemical techniques, i.e. open circuit potential (OCP), potentiodynamic polarization, electrochemical impedance measurements (EIS) and surface examination via scanning electron microscope (SEM) technique. The influence of concentration and temperature on the electrochemical behavior of TI and its alloy were also studied. The results of polarization measurements showed that corrosion current density (i_corr) increases with increasing either temperature or oxalic acid concentration for both samples. Moreover, the value of i_corr for Ti was found to be lower than that for Ti-6Al-4 V alloy, where the corrosion resistance for titanium was always higher. The effect of additives as SO₄²⁻ and Cl⁻ ions was studied; results indicated that the oxide film resistance (R_ox) value decreases with increasing the concentration of SO₄²⁻ ion. However, for Cl⁻ ion, the value of R_ox decreases with increasing Cl⁻ ion concentration up to 1 mM before it starts to increase at higher concentrations. EIS and polarization results are in good agreement with each other. The obtained results were confirmed by surface examination.     

Factors Affecting the Durability of Ti-6Al-4V/Epoxy Bonds

Factors influencing the durability of Ti-6Al-4V/epoxy interphases were studied by determining chemical and physical properties of Ti-6Al-4V adherend surfaces and by characterizing the strength and durability of Ti-6Al-4V/epoxy bonds.

Ti-6Al-4V adherend surfaces were oxidized either by chemical etch or anodization. Four principal pretreatments were studied: chromic acid anodization (CAA), sodium hydroxide anodization (SHA), phosphate fluoride acid etch (P/F) and TURCO basic etch (TURCO). The oxides were characterized by SEM, STEM, profilometry, contact angles and XPS.

All adhesive bonding was carried out using a structural epoxy, FM-300U. Both lap shear and wedge test samples were tested in hot, wet environments. The results lead to the conclusion that the interfacial area between the adhesive and adherend is the primary factor affecting bond durability.     

TiB2涂层刀具制备及干铣削Ti-6Al-4V磨损行为研究?

由于切削过程中产生高温、刀具粘结与氧化严重,钛合金切削尤其是干切削,一直是刀具行业的重大挑战之一,而在刀具表面添加涂层是提高钛合金切削刀具寿命的有效途径。利用脉冲磁控溅射技术制备了TiB2涂层刀具,以相同基体的无涂层刀具为对照,干铣削Ti-6Al-4V钛合金,切削速度从30~100 m/min变化,研究TiB2涂层刀具的切削性能与失效机理。所制备的TiB2涂层具有(100)择优取向的六方晶体结构,组织致密。涂层硬度可高达4000 HV。切削实验发现,在30 m/min的低速时,TiB2涂层刀具的切削寿命超过无涂层刀具57%之多,当切削速度加倍到60 m/min时,刀具寿命未见下降。当切削速度增加到100 m/min时,TiB2涂层刀具与无涂层刀具切削寿命相当。TiB2涂层刀具表面氧化所产生的B2O3液化膜,起自润滑作用,可充分减少钛合金的粘结,降低摩擦力。因此,在TiB2或B2O3消失之前,TiB2涂层刀具均有良好表现。在100 m/min时,切削高温造成B2O3强烈挥发,且TiB2被氧化为多孔疏松的TiO2,刀具寿命急剧下降到无涂层刀具的水平。     

Corrosion resistance of pulsed laser-treated Ti-6Al-4V implant in simulated biofluids

A commercial Ti-6Al-4V alloy was treated with a pulsed-wave Nd:YAG laser under various process conditions to obtain surface oxide layer for corrosion resistance. The corrosion behaviors of bare and laser-treated Ti-6Al-4V alloy exposed to three different simulated biofluids (SBFs), namely, (1) NaCl solution, (2) Hank's solution, and (3) Cigada solution, were studied by using the electrochemical techniques like open circuit potential (OCP), Tafel analysis, and electrochemical impedance spectroscopy (EIS). The Tafel analysis showed that the laser-treated Ti-6Al-4V specimens were more corrosion resistant than the bare specimens in any of the above SBFs. The various electrical equivalent circuit models were applied to fit the EIS results to further understand corrosion mechanisms due to different surface layers formed on the alloy surface before and after the laser treatment. Optical and AFM imaging techniques were used to evaluate the topographic and morphologic features of the alloy exposed to such SBFs. The corrosion behavior of the laser-treated surfaces was explained by the melting and solid-state oxidation processes, the morphology of the surface oxide, and the underlying alloy microstructure. It is realized during the present investigation that better corrosion resistance and surface stability can be achieved by oxide growth in solid-state, under a pulsed laser condition.     

Microstructure evolution and bonding mechanism of ZrO2 ceramic and Ti-6Al-4V alloy joints brazed by Bi2O3-B2O3-ZnO glass paste

Ceramics and metal joinings have been widely employed in aerospace, dental implants, and the electronic packaging industry for fabricating multifunctional components. In this study, the 35Bi₂O₃-50B₂O₃-15ZnO (mol.%) glass has been employed for joining the ZrO₂ ceramic and Ti-6Al-4V alloy. The effect of brazing temperature on the microstructure evolution, mechanical properties, and bonding mechanism of brazed joints has been analyzed. The microstructure of the ZrO₂/glass/Ti-6Al-4V joints and the content of Bi₄B₂O₉, Bi₂O₃ and Bi₂₄B₂O₃₉ precipitated crystals in glass were found to be dependent on the brazing temperature. The reaction product of Bi₄Ti₃O₁₂ was identified in the glass/Ti-6Al-4V interface because of the chemical reaction between the oxidized layer of Ti-6Al-4V alloy and glass. A maximum shear strength as high as 48.8 ± 5.2 MPa was obtained. Our work, thus, demonstrates that the 35Bi₂O₃-50B₂O₃-15ZnO glass is an effective bonding material for joining ZrO₂ ceramic and Ti-6Al-4V alloy under low temperature in an ambient atmosphere.     

Adhesion Tensile Testing of Environmentally Exposed Ti-6Al-4V Adherends

The structural and bonding properties of Ti-6Al-4V adherends, prepared by chromic acid anodization (CAA), were studied as a function of exposure in high-temperature environments such as vacuum, air, boiling and pressurized water, and steam. Subsequent to the environmental exposure, bonds were produced and the adhesive tensile strengths measured. Long-term exposure to high temperature, dry environments did not cause structural changes to the adherend oxide but did result in poor bond strength. The failure mode in these cases was within the oxide, which was apparently weakened by the exposure. The water-and steam-exposed oxides underwent a transition from amorphous to crystalline TiO₂ (with an accompanying change in oxide morphology); however, bond strength was maintained for moderate exposures at T ≤ 250°C. For exposure at T = 300°C, the bond strength was degraded severely. The latter result can be explained by a lack of porosity in the transformed oxide. SEM and XPS measurements were made on debonded surfaces to determine the loci of failure.     

Heat-resistant thermoplastic/ chromic acid anodized Ti-6Al-4V single lap bond evaluation

Structural, heat-resistant thermoplastic adhesives were evaluated in single lap bonds. The amorphous thermoplastics tested were polyphenylquinoxaline, glass filled Ultem polyetherimide, unfilled Ultem polyetherimide, and Victerex polyethersulfone. The adherend was chromic acid anodized Ti-6Al-4V, tested unprimed and primed with Lica 44 titanate. Initial bond strengths were similar for all adhesives. In general, Lica 44 titanate primer did not affect bond strength. Bond strength was not influenced by 170°C ageing, but 232°C ageing did decrease bond strength when polyphenylquinoxaline was the adhesive. Failure occurred primarily in the adhesive fillet and propagated into the unprimed or primed anodic oxide/polymer interphase.     

Development of hydroxyapatite coatings on laser textured 316 LSS and Ti-6Al-4V and its electrochemical behavior in SBF solution for orthopedic applications

The current work focused on the development of hydroxyapatite (HAP) coating on laser textured metallic implants using electrophoretic deposition. HAP was synthesized by sol-gel technique and its phase purity and surface morphology were confirmed by FT-IR, XRD and SEM analysis. 316 L SS and Ti-6Al-4V metal implants were polished and the surface was modified using Nd-YAG laser operating at a pulse interval of 10 ns at various overlapping rate of 0%, 25% and 50%. The laser treated surface was characterized for its surface roughness using surface profilometry and surface morphology. The surface roughness of the metallic implants was increased by increase in the overlapping rate. The prepared HAP powder was electrophoretically deposited on bare and laser textured Ti-6Al-4V and 316 L stainless steel followed by vacuum sintering at 300 °C for 2 h. Scratch analysis results showed an improvement in adhesion strength for the HAP coatings on laser treated specimens than untreated metal. Corrosion efficiency of the coated samples was studied in SBF solution using EIS and potentiodynamic polarization studies. The result from the corrosion experiments proved increased corrosion resistance property of laser textured coated samples when compared to bare alloy due to higher adhesion of HAP coating on the metal surface.     

The Durability of Adhesively-bonded Ti-6Al-4V

The durability of chromic acid-anodized Ti-6Al-4V alloy, adhesively-bonded with FM-5 supported polyimide adhesive has been studied. The performance tests compared titanium samples that had been thermally treated and bonded, and samples that were bonded and thermally treated. Following the thermal treatment, the durability was examined (1) by immersing wedge-type specimens in boiling water and measuring the crack growth and (2) by measuring the lap shear strength for single lap specimens. In the wedge tests, failure occurs within the adhesive for specimens treated at temperatures below 371°C for less than one hour. For treatments at higher temperatures and for longer periods of time, failure occurs within the anodic oxide. From the lap shear tests, the principal finding is that the lap strength decreases with increasing treatment time at constant temperature and with increasing temperature at a fixed time. For the lap specimens, failure occurs to a greater extent within the oxide as the treatment time and temperature increase. Surface analysis results indicate the formation of an aluminum fluoride species. It is reasoned that the formation of fluorine-containing materials weakens the oxide and promotes failure within the anodic oxide.     

The Durability of Adhesively-bonded Ti-6Al-4V

The durability of chromic acid-anodized Ti-6Al-4V alloy, adhesively-bonded with FM-5 supported polyimide adhesive has been studied. The performance tests compared titanium samples that had been thermally treated and bonded, and samples that were bonded and thermally treated. Following the thermal treatment, the durability was examined (1) by immersing wedge-type specimens in boiling water and measuring the crack growth and (2) by measuring the lap shear strength for single lap specimens. In the wedge tests, failure occurs within the adhesive for specimens treated at temperatures below 371°C for less than one hour. For treatments at higher temperatures and for longer periods of time, failure occurs within the anodic oxide. From the lap shear tests, the principal finding is that the lap strength decreases with increasing treatment time at constant temperature and with increasing temperature at a fixed time. For the lap specimens, failure occurs to a greater extent within the oxide as the treatment time and temperature increase. Surface analysis results indicate the formation of an aluminum fluoride species. It is reasoned that the formation of fluorine-containing materials weakens the oxide and promotes failure within the anodic oxide.     

氧化石墨烯/羟基磷灰石涂层对镁合金耐腐蚀性的影响

采用仿生法在改性模拟体液中于镁合金表面制备了羟基磷灰石(HA)涂层和氧化石墨烯/羟基磷灰石(GO/HA)复合涂层。利用扫描电子显微镜(SEM)和X射线衍射(XRD)对两种涂层进行了形貌和结构表征,通过析氢量测量、极化曲线和交流阻抗等方法分别研究了裸镁合金、含HA涂层及GO/HA涂层镁合金在pH为7.4的模拟体液(SBF)和3.5%NaCl溶液中的腐蚀行为。结果表明,氧化石墨烯增加了羟基磷灰石涂层的致密性,含GO/HA复合涂层的AZ91镁合金耐腐蚀性能最好,相对于裸镁合金,其腐蚀电流密度降低了一个数量级,析氢量降低了52%。     

环氧／纳米ZnO复合涂层对镁锂合金耐腐蚀性的影响

以聚丙烯酰胺凝胶法制备了纳米ZnO,并对其进行改性,得到了环氧/纳米ZnO复合涂层.采用XRD和SEM对环氧/纳米ZnO复合涂层进行了表征.通过极化曲线和交流阻抗研究了裸基、复合涂层以及经锡酸盐转化处理后涂覆环氧/纳米ZnO的复合涂层的耐蚀性能.结果表明:复合涂层呈明显的两相结构,纳米ZnO分布均匀;复合涂层和锡酸盐转化协同,提高了镁锂合金的耐腐蚀性能.涂层中纳米ZnO质量分数不同,对镁锂合金耐蚀性能有不同的影响,纳米ZnO质量分数为2%时,复合涂层对镁锂合金的保护作用最强.     

Structural evaluation,preliminary in vitro stability and electrochemical behavior of apatite coatings on Ti6Al4V substrates

Medical-grade alloys, such as Ti-6Al-4V, have been used for fixation of fractured bone and for the total replacement of defective bone. Their bioactivity could be improved by applying a bone-like apatite layer onto their surfaces. This, in turn, enhances their integration with the surrounding tissues upon implantation. In addition, the presence of a bioactive bone-like coating minimizes the likelihood of corrosion. Various methods are known for the formation of apatite coating onto Ti-6Al-4V, among which sputtering has shown its promise as a simple direct method. In the current work, a sputtering technique was used to develop a 300 nm-thick bone-like apatite layer onto Ti-6Al-4V. Structural composition, integrity and morphology of the as-coated and thermally treated coatings were investigated. Coated substrates were further evaluated after soaking them in a simulated body fluid (SBF) for up to 14 days. Results showed the formation of an amorphous apatite layer onto the alloy, that was further shown to partially crystallize upon heat treatment. As a result of SBF treatment, the apatite layer was found to remodel through a dissolution-precipitation mechanism due to its amorphous and non-stoichiometric nature, forming a smooth layer with better homogeneity and decreased surface roughness. Electrochemical analysis of the coated alloys showed the enhanced corrosion protection of the alloy surfaces by coating them with apatite. In addition, pre-grinding of the alloy surfaces before the formation of the coating was also found to improve the corrosion inhibition of the alloy surfaces in aqueous media.     

Sodium Hydroxide Anodization of Ti-6AI-4V Adherends

The durability of adhesively bonded titanium structures is a topic of concern in a variety of fields today. There appears to be a definite connection between durability and surface pretreatment of the adherend. A variety of pretreatments are reported for Ti-6-4^1-3. For example, the chromic acid anodization (CAA) pretreatment has received a lot of attention in creating surfaces resulting in improved durability of adhesive bonds.     

In situ corrosion monitoring of Ti–6Al–4V alloy in H2SO4/HCl mixed solution using electrochemical AFM

Electrochemical atomic force microscope (ECAFM) was employed for in situ observation of corrosion of solution annealed and furnace cooled Ti–6Al–4V titanium alloy in 0.5 mol l⁻¹ H₂SO₄ + 1 mol l⁻¹ HCl mixed solution. A scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) was also used for microstructure examination and chemical composition analysis. For solution annealed followed by furnace-cooled Ti–6Al–4V titanium alloy, selective corrosion of α phase and galvanic effect at α/β interface could be clearly observed at open circuit potential under ECAFM. A higher dissolution rate was also found in α phase than β phase on the bare Ti–6Al–4V titanium alloy. The effect of potential on the corrosion behavior was also explored. Negligible corrosion was found after potentiostatic etching at −0.5 and −0.85 V_Pt for 120 min. However, selective dissolution of α phase with respect to β phase occurred when the potential was controlled at −0.9 V_Pt. The polarity inversion during potentiostatic etching at −0.9 V_Pt was also found and discussed in this study.     

Microstructures and mechanical properties of wear-resistant titanium oxide coatings deposited on Ti-6Al-4V alloy using laser cladding

In this work, a freeze-dried TiO₂ nano-sized powder was used as the coating material and single tracks of TiO_x coating were cladded on Ti-6Al-4V substrates using a diode laser. The microstructure, chemical composition, and mechanical properties of the coatings were characterized and their relationships were explored. Coatings with structural and compositional gradients formed under a laser energy density (LED) of 20 kJ/m, while coatings with a relatively homogeneous microstructure were obtained using a LED of 30 kJ/m. The microstructure evolution was controlled by the molten pool lifetime and the intensity of convective flow during laser processing. The elastic modulus of the graded coating showed a decreasing trend from the top coating surface to the interface while that of the homogeneous coating remained constant. Our results also demonstrated that the hardness and wear resistance of the oxide coatings were up to four and ten times higher than that of the substrate.     

Preparation,scratch adhesion and anti-corrosion performance of TiO2-MgO-BHA coating on Ti6Al4V implant by plasma electrolytic oxidation technique

Bovine hydroxyapatite (BHA) (from cortical bone), was selected as the main electrolyte for plasma electrolytic oxidation (PEO) on Ti6Al4V implant. The prepared PEO coatings were examined by X-ray diffraction, field emission scanning electron microscope and energy-dispersive X-ray spectroscopy. The surface roughness, adhesion strength, wettability, surface energy and corrosion behaviour of the film were also investigated. The results show that the oxide layer (26 μm) formation on the Ti6Al4V was rough and porous. The micro-pores were filled with anatase TiO₂, cubic MgO and hexagonal BHA particles. The porous structures and the compound particles were mainly composed of Mg, O, Ca, P, Ti, Na and Al. Unlike previous coatings produced from calcium and phosphorus inorganic solutions, the coating formation from a newly developed bovine bone-derived HA electrolyte revealed an additional MgO phase in the coating layer. Moreover, higher amount of single phase hexagonal crystalline BHA phase with a Ca/P ratio of 1.1 was achieved with a single PEO process. A film-to-substrate adhesion strength of 1862.24 mN and scratch hardness of about 4.1 GPa was achieved from this method. The TiO₂/MgO/BHA film exhibited better wettability, higher surface energy and superior corrosion resistance compared to the bare Ti6Al4V substrate.     

Influence of a hard transition layer on the microstructure and properties of diamond-like carbon/hydroxyapatite composite coating prepared by magnetron sputtering

The nanostructured diamond-like carbon/hydroxyapatite composite coating (DLC/HA) was deposited using magnetron sputtering technique with a densely packed columnar cross-sectional structure and a uniform granular surface morphology. After heat treatment, the amorphous structure of the coating was transformed into a crystal structure. Nanohardness and scratch tests results demonstrated the DLC transition layer significantly enhanced the nanohardness of Ti6Al4V substrates from 4.8 GPa to 10.4 GPa, and increased critical load from 16.6 N (pure HA layer) to 26.5 N (DLC layer) without obvious brittle fracture, flaking and delamination. Electrochemical and immersion tests results demonstrated that DLC/HA composite coatings with a dense gradient transition interlayer had better corrosion resistance and could prevent harmful metal ions being released into the SBF solution more effectively than single HA coatings. Furthermore, active Ca²⁺ ions can be rapidly released from the coating surface during initial immersion in the SBF solution, and facilitated the formation of bone-like apatite.