Ti6Al4V Substrates Research Articles

Microstructure and mechanical properties of nano dual-phase TiCuNi metallic glass films achieved by modulating magnetron sputtering temperature

Nano-dual phase TiCuNi metallic glass film having amorphous matrix with some ∼8.5 nm CuTi nanograins dispersed were achieved by magnetron sputtering at deposition temperature of 200 °C. The temperatures below or above that resulted in the totally amorphous or columnar crystalline structures of as-deposited TiCuNi films, respectively. The nano dual-phase TiCuNi metallic glass film exhibited the greatest hardness of 7.5 GPa, which was greatly higher than those of the uncoated Ti6Al4V substrate, amorphous and crystalline TiCuNi films by ∼114.3%, 11.9% and 23.0%, respectively. It also performed the highest wear resistance with the lowest wear rate of 1.32 × 10−5 mm3/Nm, slower than those of the uncoated substrate, amorphous and crystalline TiCuNi by 14.3%, 5.0%, and 7.0%, respectively. This work reveals an effective method to realize nano-dual phase structure of TiCuNi metallic glass films with mechanical properties improved, which is significant for the further development of titanium-based metallic glass films.

Microstructure and properties of Cr–AlSi12 composite coatings pre-coated on Ti–6Al–4V alloy substrate via mechanical alloying and subsequent laser cladding treatment

Cr–AlSi12 composite coating on Ti–6Al–4V alloy substrate was fabricated by mechanical alloying (MA) and subsequent laser cladding (LC). The weight ratio of the mixed powders was Cr: AlSi12 = 60:40. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were applied to investigate the evolution of surface morphologies, cross-section microstructures and phase composition of the coatings before and after laser treatment. The results showed that Al8Cr5, AlCr2, (Si, Al)2Cr and Cr5Si3 were generated in the MA-LC coating through in-situ alloying reaction. The formation of Al3Ti and Ti5Si4 intermetallic compounds was caused by interdiffusion. Metallurgical bonding was achieved at the coating/substrate interface. Results of the scratch test indicated that laser treatment could significantly improve the bonding quality of the interface. Meanwhile, the microhardness of the MA-LC coating was about 3–4 times higher than that of the MA coating. The high-temperature oxidation resistance of the MA-LC Cr–AlSi12 coating was also studied. It was found that after 100 h of oxidation, the MA-LC coating could effectively enhance the oxidation resistance of the substrate. The oxide films and intermetallic phases formed during oxidation process could play a role of intense hindrance to the diffusion of oxygen into the internal Ti–6Al–4V substrate. The oxidation mechanism of the coating is discussed in detail.

Nanostructured multilayer CAE-PVD coatings based on transition metal nitrides on Ti6Al4V alloy for biomedical applications

Titanium alloys possess poor resistance to friction and this adversely affects the corrosion behavior and osseointegration of the implants made from these alloys. Nanostructured PVD coatings with biocompatibility, anti-wear and anti-corrosion characteristics have attracted much attention in biomedical applications. In this study, TiN and ZrN single layer and CrN/TiN and CrN/ZrN nanostructured multilayer thin films were applied on a Ti6Al4V substrate by means of cathodic arc PVD technique. The physical-chemical characterization of the coatings was conducted using FE-SEM, EDS, and XRD analyses. Their surface topography and wettability were measured. In addition, the hardness and adhesion strength were evaluated by means of Knoop microhardness and scratch tests, respectively. Also, the apatite-forming ability of the coatings was investigated through SEM, EDS and, FTIR. The corrosion performance of the coatings was studied using PDP and EIS assessments in SBF solution. According to the findings, the multilayer coatings have higher hardness and scratch resistance than single layers. The coating delamination tacked place in Lc equal 39.6 (N) and 39.3 (N) for CrN/TiN and CrN/ZrN coatings, respectively. The corrosion assessments revealed that the CrN/ZrN multilayer coating exhibited the best corrosion resistance due to its smoother surface and more dense structure in addition to its specific architecture. The ZrN single layer and CrN/ZrN multilayer coatings showed a better hydroxyapatite precipitation; however, all surfaces had satisfactory bioactivity. In all, this study showed that CrN/ZrN nanostructured multilayer thin film is potentially suitable candidate for orthopedic and dental implants.

Lubrication and anti-wear behavior of duplex annealed nanodiamonds/PEO coating on Ti6Al4V: Functional mechanism of structural transformation

Titanium alloys have been widely used due to its low density, high strength and excellent corrosion resistance, but the poor tribological properties restrict its engineering application. Nanodiamond particles provide excellent lubrication and high wear resistance due to the unique physical-chemical properties, but the mismatched mechanical properties severely restrict the solid lubrication application of nanodiamond for titanium alloys. In this study, plasma electrolytic oxidation coatings were firstly prepared on Ti6Al4V substrates, and core-shell annealed nanodiamond particles obtained by high-temperature annealing at 1300 °C with nanodiamond core and graphitic outer shell were deposited on the PEO coatings. The plasma electrolytic oxidation-annealed nanodiamond coatings led to a 46.67 % and 96.13 % reduction of coefficient of friction and wear volume comparing to plasma electrolytic oxidation coatings. Annealed nanodiamond with unique core-shell structure can reduce the abrasion of friction pairs; and the friction-induced structural transformation of annealed nanodiamond particles in the top-layer tribofilm further enhanced the lubrication and wear-resistance. The proposed lubrication mechanism has implications for the development of novel nanomaterials with core-shell structure and duplex coating systems for engineering applications.

Wear behavior and atomic competition mechanism of flexible wear-resistant coating with oxygen-free zone in Ti6Al4V alloy

The flexible wear-resistant coating on Ti6Al4V substrate was successfully fabricated by plasma powder cladding with Al–Si powder. The microstructure, element distribution and phase component of the flexible wear-resistant coating were characterized by the field emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS) and the X-ray diffractometer (XRD). The micro-hardness of coating was measured by micro-hardness tester. The wear-resistance of Al–Si coating was evaluated by sliding friction experiment. The prepared coatings have no cracks and a good metallurgical bonding (MB) with the substrate. The wear-resistance of the coating surface is about twice as much as that of Ti6Al4V substrate. Furthermore, the in-between MB zone has the more excellent wear-resistance (about 7 times). The oxygen free zone can be formed in the MB zone, providing a good toughness for the flexible wear-resistant coating. The wear mode is adhesive wear for the flexible wear-resistant Al–Si coatings. Based on the self-consistent bond length difference (SCBLD) method, the competition among atoms in MB zone as well as the formation mechanism of flexible oxygen free zone is investigated.

Effect of graphene addition on the performance of in-situ (TiC+TiBx)/Ti composite coatings by laser cladding: Microstructure and water droplet erosion resistance

In this study, different amounts of graphene (Gr, 0–2 wt%) were added into Ni60/Ti6Al4V powder mixtures to prepare (TiC+TiBx)/Ti composite coatings on Ti6Al4V substrates by laser cladding. By means of XRD, SEM, EDS, and TEM, the effects of Gr content on the dilution rate, phase composition, microstructure, microhardness and water droplet erosion (WDE) resistance of the coatings were comprehensively analyzed. The results showed that the coatings comprised phases of Ti2Ni, TiC, TiB, TiB2, α-Ti and β-Ti. The increased Gr content precipitated more TiC, providing more heterogeneous nucleation sites for other grains and suppressing the grain growth. The TiC-TiB2 and TiB-TiC intergrowth structures exhibited high load-bearing capacity and contributed to the synergistic hardening and strengthening effects. When the Gr content was 1 wt%, the coating had the highest microhardness of 886.3 HV0.3 and showed the best WDE resistance. The excellent performance of the hard phases, the existence of a large number of grain boundaries and the effect of the skeleton improved the WDE resistance of the coatings.

Biomimetic mineralized amorphous carbonated calcium phosphate-polycaprolactone bioadhesive composites as potential coatings on implant materials

Biomimetic mineralized (Mg, Zn, Sr) carbonated amorphous calcium phosphate (cACP) containing biodegradable polycaprolactone (PCL) coating was prepared via spin coating technology. The main role of PCL was to provide a controlled release of cACP for a prolonged period of time and to act as a bioadhesive, providing better adherence than that of pure cACP powder. The cACP and the cACP-PCL composite layers were optimized as very thin, non-continuous films on the surface of a commercial titanium alloy, maintaining its surface roughness. The powder layer and the composite film were morphologically, chemically, and biologically tested. In vitro biocompatibility measurements were performed using MC3T3-E1 cells. The cell viability significantly increased when cACP coatings and cACP-PCL composite were applied to the pure Ti6Al4V substrate. The pure PCL coating and the titanium substrate indicated similar biocompatibility, however, adding cACP powders into the polymer solution resulted in increased cell viability. LDH and ALP measurements showed a large number of living cells on the surface of all samples. The cell morphology study by Calcein/DAPI staining as well as SEM measurements demonstrated a well-adhered and spread, confluent cell monolayer. The long-term release of bioactive ions in SBF solution indicated that the biodegradability of composite coating is slightly faster than the cACP powder layer. All in vitro measurements confirmed the suitability of the developed composite layer as a potential bone substitute and bioactive coating on middle- and long-term implants.

Undoped and diamond-doped MAO coatings prepared on Ti6Al4V: Microstructure, wear, corrosion, and biocompatibility properties

In order to improve the wear resistance and biocompatibility, undoped and diamond-doped micro-arc oxidation (MAO) coatings are prepared on Ti6Al4V in this paper by using electrolyte without/with diamond nanoparticles. The microstructure, wear resistance, corrosion resistance, and cytocompatibility performance of the coatings are studied and compared. The results show that undoped and diamond-doped MAO coatings have similar surface morphologies and thicknesses. With the increase of the MAO time, the surface morphology of the two types of coatings translates from the micro-sized traditional volcano pores into Micro/Nano-pores composite structure. The diamond-doped MAO coatings have higher wear resistance than the undoped MAO coatings and the original Ti6Al4V substrate. All the MAO coatings have higher corrosion resistance than the Ti6Al4V substrate. However, the diamond doping has no obvious influence on the corrosion resistance. In vitro assays indicate that both the two kinds of MAO coatings have a better ability to enhance the adhesion, spreading, proliferation, and osteogenic differentiation of MC3T3-E1 osteoblasts compared with the original Ti6Al4V substrate. Considering the high wear resistance, the diamond-doped MAO coatings are more promising for Ti6Al4V alloy.

Microstructure and water erosion resistance of in situ synthesized (TiBx+TiC)/Ti composite coatings produced by laser cladding

(TiC + TiBx)/Ti composite coatings were prepared on a Ti6Al4V substrate by laser cladding to improve its microhardness and water erosion resistance. The 1 wt% Gr + 49 wt% Ni60 + 50 wt% Ti6Al4V composite powders were used as the precursor. The effects of laser energy density and powder deposition density on the geometric morphology, phase composition, microstructure, microhardness and water erosion resistance characteristics of the coatings were comprehensively studied through numerical simulation and experimental characterization. The results showed that the geometric morphology of the coating was determined by the laser energy density and powder deposition density; however, the microstructure of the coating was not completely understood. A high scanning speed was more conducive to grain refinement than a low scanning speed. In addition, the earlier precipitated hard phases provided heterogeneous nucleation sites for other grains and promoted their dispersion. Due to the dispersion strengthening and grain refinement effects of the in situ synthesized hard phases, the microhardness and water erosion resistance characteristics of the coatings significantly improved. With a laser energy density of 64 J mm−2 and a powder deposition density of 5 × 10−3 g mm−2, the microhardness of the coating reached 919.9 HV0.3, which was 2.8 times greater than that of the Ti6Al4V substrate. The water erosion resistance of the coating was the best.

Diamond particles-reinforced Ni-based composite coating on Ti6Al4V alloy: Microstructure, mechanical, dynamic impact and dry-sliding tribological properties

Diamond particles-reinforced Ni-based composite coating was fabricated on Ti6Al4V by vacuum cladding. The microstructure, phase composition, hardness, dynamic impact and dry-sliding tribological properties of the coating have been investigated systematically. The results demonstrate that the coating consists of a tough TixNiy/Ti3Al matrix filled with hard phases of TiC, Ti3SiC2 and TiC/CrxCy covered diamond. Benefiting from the high-temperature diffusion, the coating is well-metallurgically bonded with the substrate. Compared with the Ti6Al4V substrate, the overall macro hardness (H) and nanoindentation hardness (HIT) of Ni-based composite coating increase by 1.2 times and 3.5 times, respectively. The coating has a complete residual indentation under the high frequency of impact. Its diameter and depth are 90 % and 86 % of the substrate, respectively, indicating that the coating has relatively excellent impact toughness. Further, the coating has good wear resistance under high load. Its wear rate is 7.79 × 10−5 mm3/Nm, which is only 1/6 of the Ti6Al4V substrate. Therefore, the coating has good comprehensive performance and potential practical applications.

Durable Biomimetic Two-Tier Structured Superhydrophobic Surface with Ultralow Adhesion and Effective Antipollution Property.

Superhydrophobic surfaces with low adhesion have attracted great attention in recent years owing to their extensive applications. Enlightened by multifunctional rice leaves, a micro/nanobinary structured superhydrophobic surface was successfully fabricated on the Ti6Al4V substrate by photoetching, acid etching, alkaline etching, as well as fluorination treatments. Water droplets exhibited a Cassie impregnating wetting state on this superhydrophobic surface, under which the contact area fraction of the liquid-air interface caused by primary micron-scale stripped bumps (fp) and secondary nanoflower-like structures (fs) were calculated for the first time. The water adhesion force of this nonwetting surface was precisely measured as 7 μN, which was much lower than that (362 μN) of the original flat substrate and the previous reported surfaces. Moreover, this low-adhesive surface displayed good chemical stability after exposing to air, soaking in aqueous solutions (acid, alkaline, and salt), and cyclic icing/melting treatment. It also showed good mechanical durability after a series of abrasion treatments. Besides, this multifunctional superhydrophobic surface exhibited superior antipollution property to different kinds of contaminants. This multifunctional superhydrophobic surface displays a huge potential for industrial droplet transportation and self-cleaning applications.

Multi-objective optimization for laser cladding refractory MoNbTiZr high-entropy alloy coating on Ti6Al4V

In this study, a novel MoNbTiZr refractory high-entropy alloy (RHEA) coating was synthesized on Ti6Al4V surfaces by laser cladding (LC) with different processing parameters. The mathematical models between laser processing parameters (laser power, powder feeding rate, scanning speed) and dilution, porosity, and microhardness were developed by response surface methodology (RSM) and validated by ANOVA based on single-factor experimental results. The results show that the dilution and porosity of the coating are negatively correlated due to the significant difference in melting point between the Ti6Al4V substrate and the RHEA powder. The rise in the dilution causes a decrease in the content of the strengthening elements in the coating, which is the main reason for the sudden drop in the microhardness to 425 HV. Compared to laser power and powder feeding rate, the analyses of variance show that the scanning speed has a relatively high F-value of 70.38. Also, the dilution has a positive correlation with laser power and scanning speed, and is inversely correlated with the powder feeding rate. Finally, a multi-objective optimization in terms of dilution, porosity, and microhardness was performed, and the optimal combination of processing parameters was a laser power of 2700 W, a powder feeding rate of 8 g/min, and a scanning speed of 3 mm/s. The predicted results are in good agreement with the validation results.

Alternating electric field stimulation: Phenotype analysis and osteoclast activity of differentiated RAW 264.7 macrophages on hydroxyapatite-coated Ti6Al4V surfaces and their crosstalk with MC3T3-E1 pre-osteoblasts

Biophysical stimuli can mimic endogenous electric potentials and currents in the natural bone to enhance tissue healing and reconstruction in diseased bone. However, little is known about the influence of electric fields on osteoclasts. Therefore, this study aimed to investigate the effects of alternating electric fields on osteoclast differentiation and activity. In this in vitro study, RAW 264.7 cells were seeded on Ti6Al4V substrates, as a loadbearing implant material modified with biomimetic calcium phosphate (BCP) and stimulated towards osteoclastic differentiation via growth factors. The effects of directly coupled alternating electric fields (0.7 Vrms, 20 Hz) on cell behavior were examined for up to 28 days. Alternating electric field simulation was performed using the finite element method. Changes in cell and substrate morphology were examined via light and fluorescence imaging. Cell viability was assessed via WST-8 assay. The effect of electrical stimulation (ES) on intercellular signaling and crosstalk was evaluated using indirect co-cultures with murine MC3T3-E1 pre-osteoblasts by qPCR. Morphological analysis proved the successful differentiation of macrophages into osteoclast-like cells for both electrically stimulated samples as well as unstimulated controls. ES promoted RAW 264.7 viability within the first seven days and induced a cellular response at gene expression levels. Gradually decreased expression rates of genes related to osteoclast differentiation and activity within 28 days could indicate a long-term inhibitory effect of ES on osteoclastogenesis and osteoclast activity while significantly upregulated carbonic anhydrase type 2 expressions could be a consequence of membrane depolarization to maintain intercellular pH levels. In this context, we were also able to demonstrate the degradation of the BCP surface by cellular influence. ES affected the crosstalk between osteoblast-, and osteoclast-like cells. Supernatants of electrically stimulated RAW 264.7 specimens led to decreased MC3T3-E1 viabilities and mineralization. While osteopontin expression in MC3T3-E1 cells was significantly decreased, markers of osteogenic differentiation showed higher expression rates. Underlying biophysical mechanisms in combination with biomaterials are part of ongoing research.

Microstructure and mechanical analyses of Ti6Al4V/B4C composites on Ti6Al4V substrate: Effect of laser power on multiple track laser metal deposition

Components used in many manufacturing applications especially in the defence, automotive and aerospace are required to meet certain properties, such as elastic modulus, toughness, resistance to wear and corrosion. Additive manufacturing (AM) is a technique used for the fabrication of layer-by-layer geometries via three dimensional (3D) mechanisms at a certain process parameter. Titanium alloy and boron carbide (Ti6Al4V/B4C) composites coatings have been successfully fabricated on titanium alloy (Ti6Al4V, grade 5) by laser metal deposition (LMD) of additive manufacturing (AM) process. Microstructure analysis of the fabricated multiple clad is characterized by optical and scanning electron microscopy. The obtained multiple tracks show that the coatings are profound with TiC and TiB phases with dendrites of TiC particles in the coatings. The evolving microstructures of the deposited coatings at a laser power of 1000 W and 1200 W with a scanning speed of 1 m/min exhibit some lateral cracks which is associated to the brittle nature of ceramic boron carbide in the clad zone. The atomic level characterization of the coatings is determined through the surface roughness obtained by atomic force microscope (AFM). Microhardness analysis is performed at the cross-section surface of the coatings by Vickers pyramid indentation at 300 gf load with dwell time of 10 s on Zwick Roell microhardness tester. From the samples investigated, sample at a laser power of 1200 W has the highest hardness value of 548 HV0.3/10s.

Effect of sputtering power on the properties of TiN coatings deposited by the magnetron sputtering

In this work, the TiN coatings on Ti6Al4V and Si substrates were deposited by magnetron sputtering. The effect of sputtering powers on structure and mechanical properties of the TiN coatings was investigated. X-ray diffraction patterns displayed a single phase of face centered cubic structure. Scanning electron microscope observations found that the particle morphology of the TiN coatings changed from a leaf or flat-shaped structure to a tetrahedron faceted one, similar to a pyramid. The particle size and deposition rate increased with increasing sputtering power due to higher energy bombardment of ion gas to surface target. Furthermore, the highest hardness value (22,8 GPa ± 1,2 GPa) corresponds to the TiN coating deposited at 250 W power. Finally, the friction coefficient increased from 0,46 to 0,61 with increasing sputtering power from 150 to 300 W.

Diamond-like carbon films prepared by a low temperature periodic process for application in ventricular assist devices.

Due to the poor tribological properties of titanium (Ti) and its alloy Ti6Al4V (commonly used for ventricular assist devices manufacturing), diamond-like carbon (DLC) films with excellent anti-wear properties are pursued to improve the wear resistance of Ti and its alloys. Considering the effect of temperature on magnets inside pump impellers and workpiece deformation, DLC films are preferred to be prepared under low temperature. In this study, DLC films were prepared on Ti6Al4V alloys by periodic and continuous processes, and the corresponding maximum deposition temperature was 85 and 154°C, respectively. The periodic DLC films exhibited the feature of columnar structure, and the surface hillocks were less uniform than that of continuous DLC films. The periodic DLC films possessed more sp3 -bonded structures, and the accessorial sp3 -bonding mainly existed in the form of CH. Compared to continuous DLC films, the periodic DLC films had lower residual stress and better adhesion with Ti6Al4V substrates. Both DLC films could effectively reduce the friction coefficient and wear rate of Ti6Al4V alloys both in air and fetal bovine serum (FBS), and the periodic DLC films exhibited superior anti-wear properties to that of continuous DLC films in FBS. Haemocompatibility evaluation revealed that both DLC films presented similar levels of more human platelet adhesion and activation as compared with that of bare Ti6Al4V. However, both DLC films significantly prolonged plasma clotting time in comparison to bare Ti6Al4V. This study demonstrates the potential of low-temperature DLC films as wear-resistant surface modification for VADs.

Evaluation of in-situ synthesised titania-zirconia-boron carbide composite cladding on Ti6Al4V substrate using continuous wave fibre laser

In this work, titanium metal matrix composite (TiC, TiB2, TiO2, ZrB2) cladding was synthesised by irradiating a fibre laser beam on a mixture of Ti6Al4V alloy, ZrO2, B4C powders pre-placed on Ti6Al4V alloy plate. The effect of varying wt.% of B4C on the microstructure, hardness, erosion, and wear properties of the composite cladding were investigated using XRD, XPS, EBSD, FESEM with EDAX, nano-indentation, and wear tests. Under the exposure of fibre laser on a mixture of preplaced powders, the in-situ formation of TiC, TiB2, TiO2, and ZrB2 ceramic particles have taken place and get uniformly dispersed in the molten titanium alloy matrix. The volume fraction of these phases increases with the increasing percentage of B4C. A black willow-shaped structure (TiB2) is observed in sample BM3 (30 wt% of B4C), along with grey cellular dendrites (TiC) dispersed uniformly in the matrix. The average microhardness of the claddings increases with the increase of B4C contents. The average weight loss of the cladding samples in dry sliding wear tests decreases with increasing the B4C content. The maximum microhardness of 1582.4HV300 is recorded in BM3 cladding, which is almost four times higher than the substrate material. The decrease in the average value of maximum nano-indentation depth with an increase in the content of B4C is in good agreement with the results of microhardness tests. The hardening of the cladding is also accompanied by increased values of parameters H/E (hardness(H)/Young's modulus (E)) and H3/E2(0.133), indicating better resistance to crack formation during indentation even at higher loads showing the cladding is hard as well as tough. The grain size variation and volume fraction of TiC–TiB2 obtained from electron backscatter diffraction test results agrees with cladding having these properties. The coefficient of friction (0.15–0.25) is found to be lower than the substrate material (∼0.3). The claddings also show good erosion resistance at ambient, 250 °C, 350 °C and 750 °C.

Comprehensive Electrochemical Studies on Nanolayered Multilayered Ti/TiN and TiAl/TiAlN Coatings Deposited on Ti6Al4V Substrates

Corrosion resistance properties of Ti/TiN and TiAl/TiAlN nanolayered multilayered coatings deposited on Ti6Al4V alloy substrates by unbalanced magnetron sputtering were investigated. The coatings contain a bi-layer thickness of Ti/TiN or TiAl/TiAlN ∼3.5 nm/4 nm and the total thickness of the coating is ∼9 µm. Corrosion properties of the coatings were investigated using electrochemical impedance spectroscopy (EIS) for 30 d while immersed in 3.5 wt% NaCl solution. EIS investigation of the coatings showed that the corrosion occurred due to the penetration of electrolyte and oxygen through the micro/nanopores present in the coatings. It was found that the TiAl/TiAlN coating offered corrosion protection superior to that of the Ti/TiN coating during the immersion study. Potentiodynamic polarization studies revealed that both coatings showed passive behavior. Formation of a passive film on the coated surface during polarization enhanced the barrier properties of the coatings and provided anodic protection to the underlying alloy.

Influence of Post-Deposition Thermal Treatments on the Morpho-Structural, and Bonding Strength Characteristics of Lithium-Doped Biological-Derived Hydroxyapatite Coatings

We report on hydroxyapatite (HA) of biological-origin doped with lithium carbonate (LiC) and lithium phosphate (LiP) coatings synthesized by Pulsed laser deposition onto Ti6Al4V substrates fabricated by the Additive manufacturing technique. A detailed comparison from the structural, morphological, chemical composition, wetting behavior and bonding strength standpoints of as-deposited (NTT) and post-deposition thermal-treated (TT) coatings at temperatures ranging from 400 to 700 °C (i.e., TT400–TT700), was performed. Structural investigations indicated a complete crystallization of the initially amorphous HA-based layers at temperatures in excess of 500 °C. The morphological analyses emphasized the rough appearance of the film surfaces, consisting of particulates whose dimensions increased at higher temperatures, with an emphasis on LiC coatings. AFM investigations evidenced rough surfaces, with a clear tendency to increase in corrugation with the applied temperature, in the case of LiC coatings. A hydrophobic behavior was observed for control, NTT and TT400 samples, whilst a radical shift towards hydrophilicity was demonstrated for both types of structures at higher temperatures. In the case of TT500–TT700 coatings, the pull-out adherence values increased considerably compared to control ones. Taking into consideration the obtained results, the positive influence of post-deposition thermal treatments (performed at higher temperatures) on the physical–chemical and mechanical properties of LiC and LiP coatings was indicated. Alongside these improved characteristics observed at elevated temperatures, the sustainable nature of the used BioHA materials should recommend them as viable alternatives to synthetic HA ones for bone implant applications.

Development of ceramic coatings on titanium alloy substrate by laser cladding with pre-placed natural derived-slurry: Influence of hydroxyapatite ratio and beam power

The attraction towards Ti and its alloys reside in their superior mechanical and tribological features, as compared to CaPs, which are renowned for their compositional and structural features similar to those of natural bones. However, Ti-based materials suffer from limited biocompatibility and inertness when implanted for extended periods. As such, surface modification with ceramic coatings is required in order to achieve proper biomedical features and enhance their overall behavior in the human body. Hence, this study outlined for the first time the prospect of coating several Ti6Al4V substrates (disks) with bovine-bone derived hydroxyapatite (HA) by laser cladding technique with pre-placed slurry. During laser processing the input materials merge depending on the heating rate/temperature and clad materials. The proposed sample preparation set-up, followed for the first time in this study, involved the concomitant modulation of two parameters: the natural HA ratio (100 wt%, and 50 wt% HA + 50 wt% Ti blends) and laser beam power (500–1000 W range). The laser beam was applied after the ceramic slurries (prepared HA/HA-based blends mixed with polyvinyl alcohol) were placed inside the priorly machined channels on the metallic Ti disks. Partially overlapped cladding tracks (∼30% overlapping ratio) resulted and the investigations were further performed in cross-section view. The structural analyses confirmed the formation of calcium titanate as main phase for all samples and the arrest of HA only for those prepared with 100% HA ratio at low to medium laser powers. In addition, the morpho-compositional evaluation revealed the formation of a fully ceramic coating only for the latter sample sets. Further, the surface wettability (contact angle and surface free energy) and Vickers micro-hardness results led to the selection of the optimal technological parameters for the development of ceramic cladded layers with prospect compatibility with regenerative medicine applications.