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

Ultrasonic assisted tubular channel angular pressing process

Improvement of severe plastic deformation method׳s efficiency by decreasing the pressing load is an important challenge for industrialization of these processes. A novel severe plastic deformation technique entitled tubular channel angular pressing process was recently proposed and experimented. The current study investigates the influences of ultrasonic vibration (UV) amplitudes in axial and radial directions on the deformation behavior and required punch force of TCAP process using finite element analysis. The numerical results indicated that the magnitude of imposed effective strain and the uniformity of strain distribution are enhanced by applying ultrasonic vibration. In addition, higher UV amplitude leads to an increment of effective strain and enhancement of strain dispersal. Furthermore, the simulated results showed that application of ultrasonic vibration needs lower pressing force to carry out TCAP process. Furthermore, a much lower punch load is required by adding vibration amplitude. It is found that the influence of radial directional UV is a more dominant factor than axial one on both the strain behavior and the pressing force. It is believed that ultrasonic vibration of TCAP die is more impressive than UV of either mandrel or punch

Characterization of nanostructured pure aluminum tubes produced by tubular channel angular pressing (TCAP)

Ultrafine grained (UFG) aluminum tubes were fabricated by the tubular channel angular pressing (TCAP) process. The microstructural evolution was characterized by transmission electron microscopy (TEM) and mechanical properties were evaluated by compression test and hardness measurements. TEM analysis of specimen subjected to one TCAP pass showed the formation of an array of elongated subgrains with high angle grain boundaries. Increase in the number of passes changes the elongated grains to equiaxed grains with ~310 nm sizes. Microhardness value of the processed tubes was enhanced to 49.4 Hv after one pass from an initial value of 32.9 Hv. Yield and ultimate strengths were increased 2.5 and 2.28 times as compared to annealed specimen. Compression tests also showed that UFG aluminum tubes exhibit lower work hardening and almost perfect plastic behavior without any failure

Parameter optimization of sputtered Ti interlayer using Taguchi method

The aim of this study was to optimize the process of coating a thin Ti film using a PVD magnetron sputtering system. The Ti thin film acted as an interlayer sandwiched between a substrate and a hard TiSiN coating. The substrates used were glass and high speed steel (HSS). An optimization of the process input parameters was carried out by utilizing Taguchi method. Morphological studies on the resultant coating were done using a field emission scanning electron microscopy (SEM). X-ray diffraction was utilized to analyze the crystal structure of the thin film. Micro scratch test was used to determine the adhesion strength of the coating/substrate system. Thin film Ti interlayers were successfully deposited on the substrates. The subsequent deposited TiSiN coatings on the substrates were very dense and uniform. The optimized input parameters of the Ti interlayer deposition resulted in an improved adhesion strength of the TiSiN coating on the substrate by 28.5%

Recent development of calcium phosphate based coating on titanium alloy implants

Titanium alloy implants are widely employed in biomedical devices and components, especially as hard tissue replacements as well as orthopaedic applications, owing to their favourable properties such as high-strength to weight ratio, low density, low Young’s modulus and biocompatibility. However, metallic implants cannot meet all of the clinical requirements. Therefore, in order to increase their clinical success and long term stability in the physiological environment, surface modification is often performed. This review focuses on the latest achievements in the field of surface modification techniques including sol-gel, thermal spray, magnetron sputtering, electrophoretic deposition and micro-arc oxidation of biocompatible calcium phosphates (CaP) based ceramics coatings for metallic implants with emphasis on the structure, morphological characterization, phase transformation and coating composition. A reflection on the results shows that CaP coatings can be grown with the each type of techniques and a stronger fixation can be enhanced with CaP fabrication on metallic implants. Advantages and limitations of the aforementioned techniques of CaP-based coatings from the point of view of the process simplicity as well as the most important challenges of each coating techniques are highlighted. Further, the most promising method for CaP deposition was identified and a specific area for improvement was discussed

TEM analysis and determination of dislocation densities in nanostructured copper tube produced via parallel tubular channel angular pressing process

Parallel tubular channel angular pressing (PTCAP) is a recently developed novel intense plastic deformation method appropriate for fabrication ultrafine-grained and nanostructured cylindrical tubes. In the present work a commercially pure copper was processed via multi-pass PTCAP and the effects of number of passes on grain refinement and the dislocation density were studied. TEM analysis showed that after first pass elongated subgrains with interior tangled dislocations were formed. After pass number two the density of interior dislocations through the elongated grains was decreased. In the next stages of deformation, at pass number three, elongated grains almost disappeared and equiaxed grains with grain size about 150 nm are formed as a result of dynamic recovery. The dislocation densities were measured by hardness indentation size effect using the Nix–Gao model. The results showed that increase in the number of PTCAP passes leads to decrease in the dislocation densities. The dislocation density is decreased to 2.48×109 cm−2 after fourth passes from 18.1×109 cm−2 after first pass. TEM results verified calculated values from the Nix–Gao model. Microhardness of the PTCAP processed tube through four passes increased to ∼142 HV from initial value of about 62 HV. Also, significant increase takes place after single pass and in the next passes the hardness value is saturated

Not-yet-designed multilayer Nb/HA/MWCNT-Au/Se/AuNPs and NbO2/HA/GO/Se biocomposites coated Ti6Al7Nb implant

Increased commercial demands of appropriate bone materials, smart multilayer biocomposites named niobium/hydroxyapatite/multiwall carbon nanotube hybrid gold/selenium/gold nanoparticles (Nb/HA/MWCNT-Au/Se/AuNPs) and niobium oxide/hydroxyapatite/graphene oxide/selenium (NbO2/HA/GO/Se) support Ti-6Al-7Nb implant alloy (Ti67IMP). Adhesion strength of primary as-deposited films was assessed by micro-scratch nanomaterial analysis. The microstructure, phase and elemental features of developed large-surface-area composites were characterized via FESEM, TEM/HRTEM, XPS, XRD/GIXRD, Raman and FT-IR techniques. Besides, in-vitro bioactivity study of reinforced Ti67IMP in simulated body fluid (SBF) media followed to evaluate the enhanced potential of bone-like apatite layer formation on treated surfaces comparatively. The designed multilayer biofilm-Ti67IMP systems may contribute to facilitate low-risk bone regeneration with antibacterial and drug delivery potential and long-term mechanical satisfaction

The tribological and electrochemical behavior of HVOF-sprayed Cr3C2–NiCr ceramic coating on carbon steel

High Velocity Oxygen Fuel (HVOF) is an excellent approach to prepare a good, wear-resistant lamella of Chromium Carbide-Nickel Chrome (Cr3C2-NiCr) on carbon steel for high temperature application. This research investigates the effect of a thin, deposited layer of Cr3C2-NiCr on carbon steel in terms of wear and corrosion properties. The microstructure of the HVOF-sprayed Cr3C2-NiCr coating was characterized at each step by scanning electron microscopy. Wear testing was performed with a pin-on-disk tester. Wear weight loss was examined by applying different loads over a 9048.96 m sliding distance. Experimental results show that the wear resistance of the coated sample reduced the risk of seizure compared to the uncoated sample. An electrochemical test was also performed and the behavior of the substrate in the coated sample was investigated in 3.5 NaCl for 27 days. Electrochemical Impedance Spectroscopy (EIS) showed that the HVOF coating has high corrosion resistance and protects the substrate from NaCl electrolyte penetration. So deposition this layer of ceramic composite is protected oil piping from synergistic attack of seawater during the transport of crude oil to the refinery. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Excellent energy absorption capacity of nanostructured Cu–Zn thin-walled tube

The present study shows that nanostructured (NS) thin-walled tubes possess an excellent energy absorption capacity, which was increased about four times compared to their course grained counterparts. Different deformation modes of axisymmetric concertina folding, three lobes diamond, and two lobe diamond forms were observed in annealed, single pass and two pass parallel tubular channel angular pressing (PTCAP) processed tubes, respectively

Low-velocity impact damage of woven fabric composites: Finite element simulation and experimental verification

This paper addresses the response of Glass Fiber Reinforced Plastic laminates (GFRPs) under low-velocity impact. Experimental tests were performed according to ASTM: D5628 for different initial impact energy levels ranging from 9.8 J to 29.4 J and specimen thicknesses of 2, 3 and 4 mm. The impact damage process and contact stiffness were studied incrementally until a perforation phase of the layered compounds occurred, in line with a force–deflection diagram and imaging of impacted laminates. The influence that impact parameters such as velocity and initial energy had on deflection and damage of the test specimens was investigated. Finite Element Simulation (FES) was done using MSC. MARC® was additionally carried out to understand the impact mechanism and correlation between these parameters and the induced damage. The simulation and experimental results reached good accord regarding maximum contact force and contact time with insignificant amount of damage