Search

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Titanium alloys are characterised by poor tribological properties, and a ceramic TiO2 layer formed on the surface can greatly improve its performance. By pre-depositing a gold layer on the titanium surface, the gold particles promoted the outward diffusion of titanium in the ceramic conversion treatment to react with the inward-coming oxygen to form a compact titanium dioxide layer. The surface morphology, microstructure, and phase constituents were characterised by SEM/EDX and XRD. The adhesion of the oxide layers was assessed by a scratch test. The distribution of gold particles in the oxide layer enhanced the surface hardness and reduced the friction and wear against a WC (tungsten carbide) ball in the reciprocal tribological test. The ceramic conversion process was accelerated efficiently at 620–660 °C, and the more gold pre-deposited, the thicker the oxide layer. [ABSTRACT FROM AUTHOR]

It is well known that applying Ni Ti intermetallic coatings on the surface of different alloys can improve their tribological behavior. In this paper, various intermetallic phases of Ni 3 Ti, NiTi, and NiTi 2 and a Ti-rich pearlite-like eutectoid structure were in situ synthesized on the surface of commercially pure (CP) titanium grade 2. Nickel electroplating was performed on titanium samples followed by heat treatment at a temperature of 800 °C for various times up to 8 h. The formation of various phases and structures along the depth were studied using SEM, EDS and XRD. Heat treatment at a temperature of 800 °C for 4 h resulted in the formation of a multi-layered composite of Ni 3 Ti, NiTi, and NiTi 2 intermetallic films with a thickness of 5, 9, and 2 μm, respectively. A nickel diffusion layer (NDL) with a pearlitic structure containing nanolayers of αTi-NiTi 2 was also formed beneath the NiTi 2 layer even after 30 min of heating. Among the different layers formed on the surface of CP-Ti, the titanium-rich NiTi (51–52 at.% Ti) showed the highest hardness of more than 400 HV. Sliding wear tests were performed under a normal load of 10 N and the surfaces of wear tracks were studied using SEM. The results showed higher wear resistance of all intermetallic layers and NDL than the titanium substrate, with the highest wear resistance for Ni 3 Ti top layer. • Raising the heat treatment temperature reduced Ni 3 Ti thickness, increased NiTi, and kept Ni 2 Ti unchanged. • Eutectoid Ti+NiTi 2 and a proeutectoid region with ∼300 HV hardness were detected beneath NiTi 2. • The dense NiTi film had a hardness of 420 HV, while porous Ni 3 Ti measured 250 HV. • Ti-rich NiTi phase (mostly B19') was worn out through plastic deformation. • All developed layers had lower wear than the substrate, with Ni 3 Ti showing the lowest. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) or laser powder bed fusion (L-PBF), which is one of the additive manufacturing methods, has gained much more importance in recent years. Commercially pure titanium (Cp-Ti) is commonly used for biomedical applications in this process but it exhibits poor wear and friction properties during its use. Therefore, this study aims to improve the mechanical and tribological properties of Cp-Ti produced by L-PBF and forging using plasma oxidation treatment in a glow discharge environment. For this purpose, Cp-Ti samples were plasma oxidized at 650 °C and 750 °C for 1 h and 4 h and their structural and mechanical properties were characterized by XRD, SEM, 3D profilometer and micro-hardness tester. Wear tests were carried out under dry and simulated body fluid (SBF) conditions by a pin-on-disk tribometer. Cp-Ti samples by forging exhibited α-hexagonal close-packed (hcp) crystal structure, whereas Cp-Ti samples by L-PBF showed acicular martensitic α'. The phase analyses and cross-sectional investigations revealed that a TiO 2 layer formed on the surface of samples after plasma oxidation and their thickness was same for both Cp-Ti samples produced by L-PBF and forging. However, Cp-Ti by L-PBF showed higher diffusion zone depth and hardness than that of Cp-Ti by forging. It was deduced from analyses that finer grains occurred in L-PBF process and these grains led to increase diffusion zone depth by providing alternative diffusion paths for oxygen. Also, L-PBF showed better wear resistance than that of plasma oxidized Cp-Ti samples by forging in both dry and SBF conditions due to its superior hardness, high diffusion zone depth and acicular martensitic α' microstructure. • Cp-Ti samples were produced by forging and selective laser melting (SLM) / laser powder bed fusion (L-PBF). • Plasma oxidation treatment was applied to the samples at different temperatures and times. • The samples produced by L-PBF exhibited better plasma oxidation behavior than the forged samples. • The combined effects of L-PBF and plasma oxidation improved the wear resistance of the material. [ABSTRACT FROM AUTHOR]

Hardfacing layers developed by tungsten inert gas (TIG) surface melting on commercial purity titanium (CP-Ti) placing with a mixture of Fe, C and Si powders under two different traverse speeds (1 mm/s and 2 mm/s) and energy input of 1080 J/mm in an argon gas environment were investigated in terms of surface condition, microstructure, hardness and wear of the processed tracks. The surface appearance of treated layers was found to be free from any obvious defect. The TIG hardfacing layer produced dendritic structure due to dissolution of preplaced powder in the Ti melt. A maximum microhardness value of 630 HV0.5 was found on the surface layer processed with lower speed which was 2.5 to 3.5 times higher than the base material. Ball-on-plate wear tests exhibited better performance of the hardfacing layer than the untreated CP-Ti which is attributed to the presence of carbides and silicides in the Ti melt.

Abstract Commercially pure titanium (Cp-Ti) is commonly used in different applications due to its good structural properties but its low mechanical and tribological properties restrict its usage areas. Therefore, different surface modifications based on TiO 2 formation on material surfaces are applied to enhance surface features of materials. In this study, TiO 2 films were produced on Cp-Ti by sol-gel and successive ionic layer adsorption and reaction (SILAR) methods to compare the effectiveness of these methods. The structural, morphological and mechanical features of TiO 2 films were investigated by XRD, SEM and nano-indentation tester. The tribological features of coatings were characterized by using a pin-on-disk tribotester. The electrochemical behavior of TiO 2 coatings was determined by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses. The structural and mechanical analyses showed that sol-gel method caused the formation of more stable and hard film structures with good adhesion in comparison to SILAR method. For that reason, TiO 2 films produced by sol–gel process exhibited better wear and corrosion resistance than the films produced by SILAR. Highlights • TiO 2 films were deposited on Cp-Ti by the sol-gel and SILAR methods. • Corrosion and wear properties of TiO 2 films were investigated. • TiO 2 films by sol-gel showed better wear resistance due to their high hardness. • Corrosion resistance of Cp-Ti improved with TiO 2 films formed by two methods. [ABSTRACT FROM AUTHOR]

316L stainless steel is commonly used in biomedical applications. However, its use is limited because of its insufficient tribological properties. In this study, a duplex surface modification process of laser melting and plasma nitriding is proposed and wear characteristics of coated 316L stainless steel were investigated. Titanium layers were produced on 316L steel samples at laser powers of 20 and 40 W by selective laser melting. The obtained films were plasma nitrided at 650 and 750 °C for 4 h under a gas mixture of 50% N 2 –50% H 2 . The structural, mechanical, morphological and tribological properties of untreated and processed samples were examined. It was observed that the hardness and wear resistance of coated and plasma nitrided samples were higher than the uncoated and Ti coated samples due to the formation of titanium nitride phases during nitridation. Also, the results indicated that wear resistance of Ti coated and plasma nitrided samples improved with increasing plasma nitriding temperature and laser power. [ABSTRACT FROM AUTHOR]

In the present paper, the influences of different double layer on wear and scratch performances of commercially pure Titanium (CP-Ti) were investigated. TiO2/SiO2 and SiO2/TiO2 double layer coatings were deposited on CP-Ti by sol-gel dip coating process and calcined at 750C. The phase structure, cross-sectional morphology, composition, wear track morphologies, adhesion properties, hardness and roughness of uncoated and coated samples were characterized with X-ray diffraction, scanning electron microscopy (SEM), nano-indentation technique, scratch tester and 3D profilometer. Also, the tribological performances of all samples were investigated by a pin-on-disc tribo-tester against Al2O3 ball. Results showed that hardness, elastic modulus and adhesion resistance of double layer coated samples were higher than untreated CP-Ti. It was found that these properties of TiO2/SiO2 double layer coatings have higher than SiO2/TiO2 double layer coating. Additionally, the lowest friction coefficient and wear rates were obtained from TiO2/SiO2 double layer coatings. Therefore, it was seen that phase structure, hardness and film adhesion are important factors on the tribological properties of double layer coatings. [ABSTRACT FROM AUTHOR]

Abstract: Commercially pure titanium (CP-Ti) is commonly used as an implant material especially for orthopedic and dental treatments in biomedical applications. This material shows insufficient tribological properties. Some surface treatments were applied on surface CP-Ti in order to improve tribological properties of the CP-Ti. Among these techniques, sol–gel coating process was used for this purpose. In this study, CP-Ti was coated by TiO2 film with sol–gel dip coating process. Coated samples were calcined at the various temperatures. The effects of calcination temperature on the wear performance of the coated films were observed. It was observed that the hardness, elastic modulus, surface roughness, friction coefficient and wear resistance values of coated samples were higher than the uncoated CP-Ti values. Also, these properties of coated samples increased with increasing of calcination temperature. The intensity of the rutile-TiO2 phase increased with the calcination temperatures. It was determined that rutile-TiO2 structure showed self-lubrication like behavior. The best tribological properties were obtained from the sample calcinated at 900°C. [Copyright &y& Elsevier]

Abstract: TiO2 coatings were formed on the surface of CP-Ti by AC pulse micro-arc oxidation. The structural, mechanical, corrosion and tribological properties were analyzed by using XRD, SEM, microhardness tester, surface profilometer, electrochemical polarization unit and pin-on-disk tribotester. Potential, solution, frequency and duration time were chosen as the coating parameters and three levels for each parameter were determined. By determining the corrosion current density, corrosion potential, wear rate, friction coefficient and surface hardness, the optimum working conditions were determined by using a Taguchi design of experiment. After micro-arc oxidation, the aim is to minimize current density, the friction coefficient and the wear rate and to maximize corrosion potential and surface hardness after micro-arc oxidation. While the optimum conditions were determined, due to existence of more than one goal, a trade-off among goals was considered. First of all, each goal was optimized separately, and then all the goals were optimized together, considering the priority of the goals. [ABSTRACT FROM AUTHOR]