• Corrosion Science and Technology
• /
• v.20 no.6
• /
• pp.475-483
• /
• 2021

Additively manufactured titanium alloy is one of the promising materials in advanced medical industries. However, these additively manufactured alloys show corrosion properties different from those of conventional materials due to their unique microstructure. In this study, the effect of surface roughness and masking conditions on the results of the potentiodynamic polarization tests on additively manufactured or conventional Ti-6Al-4V alloys in artificial saliva solution with or without fluoride was investigated. The results showed that the corrosion potential was slightly lower with a flat cell with an O-ring than with masking tape. The corrosion rate was decreased with decreases in the surface roughness. Localized corrosion involving delamination of the surface layer occurred at 7 ~ 9 V (SSC) on the additively manufactured alloy in solution with or without fluoride when the samples were finished with 1000-grit SiC paper, whereas localized corrosion was not observed in the specimens finished with 1-㎛ alumina paste.

• Journal of Welding and Joining
• /
• v.33 no.2
• /
• pp.1-7
• /
• 2015

This article describes the basic technical concepts for applying the friction stir welding (FSW) process to titanium and its alloys. Titanium and its alloys are demanding applications of FSW. During FSW, a protective atmosphere is needed at the welding region to prevent the joints from oxidation due to the absorption of interstitial elements (O, N, and H) at high temperature. The process parameters for FSW have great influence on the microstructure and properties of the joints. No phase transformation occurred in CP Ti because FSW was achieved below the ${\beta}$-transus temperature. Therefore, the mechanical properties of the joints with CP Ti were governed by recrystallization and grain refinement. Furthermore, the strong crystallographic texture indicating <0001>//ND formed in the stir zone. On the other hands, the phase transformation occurred in Ti-6Al-4V alloy because the process temperature reached above ${\beta}$-transus temperature. For this reason, the mechanical properties of the joints with Ti-6Al-4V alloy were altered by not only recry stallization and grain refinement but also phase transformation during FSW. Engineers who want to get sound FSW joints with Ti-6Al-4V alloy have to pay attention to the control about process conditions.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1089-1090
• /
• 2006

Biomimetic apatite deposition behaviors on Zr-1Nb and Ti-6Al-4V plate with various surface conditions were examined. Both alloys were polished with abrasive papers to have different roughness and some of them were treated in NaOH before exposition in simulated body fluid. NaOH treatment was found to enhance the deposition rate of apatite on Ti-6Al-4V significantly. On the other hand, the deposition rate of Zr-1Nb was not influenced by NaOH treatment. Without NaOH treatment, the polished Zr-1Nb with abrasive paper was found to induce more apatite nucleation than the polished Zr-6Al-4V.

• Journal of Technologic Dentistry
• /
• v.23 no.1
• /
• pp.55-64
• /
• 2001

This study is focusing on the improvement of problems of Ti-6Al-4V alloy. A new Ti based alloy, Ti-15Sn-4Nb, have designed to examine any possibility of improving the mechanical properties and biocompatibility. Specimens of Ti alloys were melted in vacuum arc furnace and homogenized at $100^{\circ}C$ for 24h. All specimens were solution treated at $812^{\circ}C$ and aged at $500^{\circ}C$ for 10h. The corrosion resistance of Ti alloys was evaluated by potentiodynamic polarization test and immersion test inl%Lactic acid solutions. Ti-15Sn-4Nb system alloys showed Widmanstatten microstructure after solution treatment which is typical microstructure of ${\alpha}+{\beta}$ type Ti alloys. Analysing the corrosion resistance of Ti alloys, it was concluded that the passive films of Ti-15Sn-4Nb system alloys are more stable than that of Ti-6Al-4V alloys. Also, the corrosion resistance of Ti-15Sn-4Nb system alloys was improved with adding elements, Hf. It was analysed that the passive film of the Ti-15Sn-4Nb alloy which was formed in air atmosphere was consisted of TiO2, SnO and NbO through X-ray photoelectron spectroscopy(XPS) analysis.

• Corrosion Science and Technology
• /
• v.22 no.4
• /
• pp.257-264
• /
• 2023

Ti-6Al-4V alloys are mainly used as dental materials due to their excellent biocompatibility, corrosion resistance, and chemical stability. However, they have a low bioactivity with bioinertness in the body. Therefore, they could not directly bond with human bone. To improve their applications, their bone bonding ability and bone formation capacity should be improved. Thus, the objective of this study was to improve the bioinert surface of titanium alloy substrate to show bioactive characteristics by performing surface modification using wollastonite powder. Commercial bioactive wollastonite powder was successfully deposited onto Ti-6Al-4V alloy using a room temperature spray process. It was found that wollastonite-coated layer showed homogeneous microstructure and uniform thickness. Corrosion resistance of Ti-6Al-4V alloy was also improved by plasma electrolytic oxidation treatment. Its wettability and bioactivity were also greatly increased by wollastonite coating. Results of this study indicate that both plasma electrolytic oxidation treatment and wollastonite coating by room temperature spray process could be used to improve surface bioactivity of Ti-6Al-4V alloy substrate.

• Corrosion Science and Technology
• /
• v.8 no.4
• /
• pp.162-169
• /
• 2009

Pure titanium and its alloys are drastically used in implant materials due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus than cortical bone. Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. For this reason, Ti-30Ta-xZr alloy systems have been studied in this study. The Ti-30Ta containing Zr(5, 10 and 15 wt%) were 10 times melted to improve chemical homogeneity by using a vacuum furnace and then homogenized for 24 hrs at $1000^{\circ}C$. The specimens were cut and polished for corrosion test and Ti coating and then coated with TiN, respectively, by using DC magnetron sputtering method. The analyses of coated surface were carried out by field emission scanning electron microscope(FE-SEM). The electrochemical characteristics were examined using potentiodynamic (- 1500 mV~+ 2000 mV) and AC impedance spectroscopy(100 kHz~10 mHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The equiaxed structure was changed to needle-like structure with increasing Zr content. The surface defects and structures were covered with TiN/Ti coated layer. From the polarization behavior in 0.9% NaCl solution, The corrosion current density of Ti-30Ta-xZr alloys decreased as Zr content increased, whereas, the corrosion potential of Ti-30Ta-xZr alloys increased as Zr content increased. The corrosion resistance of TiN/Ti-coated Ti-30Ta-xZr alloys were higher than that of the TiN-coated Ti-30Ta-xZr alloys. From the AC impedance in 0.9% NaCl solution, polarization resistance($R_p$) value of TiN/Ti coated Ti-30Ta-xZr alloys showed higher than that of TiN-coated Ti-30Ta-xZr alloys.

• Journal of Powder Materials
• /
• v.28 no.5
• /
• pp.417-422
• /
• 2021

In the present work, Inconel 718 alloy is additively manufactured on the Ti-6Al-4V alloy, and a functionally graded material is built between Inconel 718 and Ti-6Al-4V alloys. The vanadium interlayer is applied to prevent the formation of detrimental intermetallic compounds between Ti-6Al-4V and Inconel 718 by direct joining. The additive manufacturing of Inconel 718 alloy is performed by changing the laser power and scan speed. The microstructures of the joint interface are characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and micro X-ray diffraction. Additive manufacturing is successfully performed by changing the energy input. The micro Vickers hardness of the additive manufactured Inconel 718 dramatically increased owing to the presence of the Cr-oxide phase, which is formed by the difference in energy input.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2017.05a
• /
• pp.79-79
• /
• 2017

Metallic biomaterials have been mainly used for the fabrication of medical devices for the replacement of hard tissue such as artificial hip joints, bone plates, and dental implants. Because they are very reliable on the viewpoint of mechanical performance. This trend is expected to continue. Especially, Ti and Ti alloys are bioinert. So, they do not chemically bond to the bone, whereas they physically bond with bone tissue. For their poor surface biocompatibility, the surface of Ti alloys has to be modified to improve the surface osteoinductivity. Recently, ceramic-like coatings on titanium, produced by plasma electrolytic oxidation (PEO), have been developed with calciumand phosphorus-enriched surfaces. A lso included the influences of coatings, which can accelerate healing and cell integration, as well as improve tribological properties. However, the adhesions of these coatings to the Ti surface need to be improved for clinical use. Particularly Silicon (Si) has been found to be essential for normal bone, cartilage growth and development. This hydroxyapatite, modified with the inclusion of small concentrations of silicon has been demonstrating to improve the osteoblast proliferation and the bone extracellular matrix production. Strontium-containing hydroxyapatite (Sr-HA) was designed as a filling material to improve the biocompatibility of bone cement. In vitro, the presence of strontium in the coating enhances osteoblast activity and differentiation, whereas it inhibits osteoclast production and proliferation. The objective of this work was to study Morphology of bone-like apatite formation on Sr and Si-doped hydroxyapatite surface of Ti-6Al-4V alloy after plasma electrolytic oxidation. Anodized alloys was prepared at 270V~300V voltages with various concentrations of Si and Sr ions. Bone-like apatite formation was carried out in SBF solution. The morphology of PEO, phase and composition of oxide surface of Ti-6Al-4V alloys were examined by FE-SEM, EDS, and XRD.

• Corrosion Science and Technology
• /
• v.9 no.1
• /
• pp.12-15
• /
• 2010

Ti-13Nb-13Zr (TNZ) alloy has attracted considerable research attention in the last decade as a suitable substitute for the commercially used Ti-6Al-4V (TAV) alloy for orthopedic and dental implant applications. Hence, in the present work, a comparative evaluation has been performed on the electrochemical corrosion behavior of TNZ and TAV alloys in 0.9 wt.% NaCl solution. The result of the study showed that both the alloys had similar electrochemical behavior. The corrosion resistance of TAV alloy is found to be marginally superior to that of TNZ alloy.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.2
• /
• pp.38-44
• /
• 2008

Titanium and its alloys, due to their superior properties of high specific strength and excellent corrosion resistance, are increasingly used in living applications in the 21century. The applications in aerospace and medical industries demand machining process more frequently to obtain a desired product. But unfortunately, this material is one of the most difficult-to-cut. In the turning process of titanium alloys, the key point for successful work is to select proper tool materials and cutting conditions. This study suggests a guidance for selecting the tool materials and the cutting speeds to improve tool life and surface integrity in Ti-6Al-4V titanium turning process. The experiments investigate the change of surface roughnesses, cutting forces and flank wear with various cutting parameters of tool materials, depth of cuts and feeds. As the results, K10 type of insert tip was assured as the best for turning of Ti-6Al-4V titanium alloy.