Bioceramics deposition on medical devices is a widespread area of research for biomedical industries since such deposits can induce excellent chemical and biological properties to the devices. Thermal spraying has been a popular choice for developing coatings to enhance the mechanical, chemical, and biological responses of medical devices. However, the high heat involved during the thermal spraying of bioceramics limits their functionality. In this context, low processing temperature in cold spraying is believed to protect the bioceramics from degradation. However, depositing bioceramics using cold spray and achieving good mechanical properties are still challenging tasks because of their poor ductility. Therefore, bio metal matrix composites with reinforced bioceramics produced using cold spray are expected to give good mechanical, chemical, and biological properties. The present work presents deposition and microstructural characterization of titanium/hydroxyapatite (Ti/HA) and titanium/baghdadite (Ti/BAG) composite coatings by cold spraying. Furthermore, the comparative corrosion response of these coatings under a simulated body fluid environment is reported. The effect of laser remelting on microstructure and corrosion behavior is also discussed.

The enhancement of the surface characteristics and corrosion resistance of cobalt alloys is under continuous examination for its biomedical applications. In this work, the investigation of corrosion performance of cobalt alloy coated with HA and HA/ZnO reinforced powders using plasma spray technique revealed that on the continuous increase of ZnO reinforcement the corrosion resistance improved progressively. The increment in surface hardness and drop in surface roughness was examined with the rise in ZnO content. Each coated sample exhibits a hydrophilic property. According to SEM and EDX investigations, homogeneous distribution of HA/ZnO coatings and intact reinforcement of ZnO in pure HA powder was noticed. All of the coated specimens maintain their morphological integrity, ensuring excellent protection of the prepared samples. The obtained outcomes denote HA/ZnO reinforced coatings on CoCr alloy as a suitable combination of enhanced surface properties and excellent corrosion resistance for future bone implant practices.

This study aims at investigating the antiviral properties of HAp/Titania composite coating. TiO 2 has promising photocatalytic activity and good efficiency in destroying the bacteria, and various viral species. SPPS is an emerging technology which can use solution to synthesis oxides. This study is focused to understand the basic mechanism of titanium complex and coating formation method in order to produce oxygen deficient type visible light sensitive coating. Coating surface was studied using XPS, UPS and REELS to understand the electronic structure and optical properties. XPS result indicated the crystallinity of HAp coating has increased as compared to conventional plasma sprayed coating and Ti 3+ species & oxygen vacancy was formed on the surface of the titania coating which can act as a charge trap. Band gap, ionization energy and electron affinity of the coating were also evaluated to further support the photocatalytic performance of this coating. There was increment in optical absorption area on the coating surface from rutile & anatase form of TiO 2 . Antiviral test will be carried out to reveal its virucidal effectiveness.

In the last 15 years, the cold spray process has demonstrated a great efficiency for the deposition of metallic powders. In this case, the consolidation of coatings is achieved thanks to the high kinetic energy of unmelted particles exhibiting a ductile behaviour. Dealing with ceramics, cold spray is also of great interest because one can expect properties not reachable with classical thermal spray technologies thanks to lower involved temperatures. However, cold spray of ceramics still remains challenging because of the ceramics intrinsic brittleness. Here, in the specific case of hydroxyapatite and to overcome this brittleness issue, we investigate the role of an intermediate PEEK layer between the substrate and the deposit. We highlight how this sublayer previously deposited by FS or air APS spraying can help improving the consolidation of the coating and its growth.

This study investigates the effect of composition on the antibacterial and antiviral properties of hydroxyapatite/titania composite coatings deposited by suspension plasma spraying. Hydroxyapatite is a bioceramic material used as a plasma-sprayed coating to promote osseointegration of femoral stems. TiO2 has promising photocatalytic activity and good efficiency in destroying bacteria, viral species, and parasites. Prior to coating, substrates were grit blasted, ultrasonically cleaned, and heated to enhance adhesion strength. The microstructure of the resulting coatings was then characterized using XRD and Raman spectroscopy. Test results indicated that SPS transformed Ti2O3 into TiO2 with mixed phases. Ti4O7 and Ti3O5 phases were also identified, which show photocatalytic activity due to oxygen vacancies. Antibacterial and antiviral tests were conducted as well.

Tensile and shear adhesion strength tests were carried out to evaluate interfacial strength between hydroxyapatite (HA) coatings and titanium alloy substrates that that had been anodized or pre or post heat treated. Tensile and shear adhesion strength were both found to be influenced by pre and post heat treating, but not by anodization. The findings suggest that it is possible to estimate tensile adhesion strength from shear adhesion test results and that the interfacial strength of coatings must be measured directly, without using an adhesive.

Metallic implants for orthopedic or dental use are often coated with a plasma-sprayed hydroxyapatite (HA) layer. In this study, HA coatings are applied to titanium substrates of varying thickness and laser shock adhesion tests are performed using different laser spot diameters. The objective is to investigate the effect of different shockwave regimes on interfacial debonding and the potential consequences of laser shock adhesion testing. HA coatings exhibiting different levels of adhesion were subjected to laser shock experiments and subsequently examined using nondestructive inspection techniques. The results are presented along with suggestions for developing a robust laser shock adhesion test.

This study assesses the influence of atmospheric plasma spraying parameters on splat stacking and porosity formation in bioglass coatings prepared from commercial powders. Coating samples were deposited on stainless steel substrates using spraying parameters established through numerical simulations. Different Ar-H 2 mixtures were used as the forming gas, and plasma current and spraying distance were varied. Coating microstructure and phase composition were determined by SEM and XRD analysis. Although numerical simulations for each parameter set predicted a suitable Sommerfeld number for proper splat stacking, Na 2 O and P 2 O 5 volatilization occurred during spraying, promoting the formation of porosity in the coatings. Denser coatings were obtained, however, by adjusting the gas mixture ratio, plasma current, and spraying distance such that enthalpy of the plasma jet is sufficient to overcome the glass transition temperature of the powder and at the same time avoid the evaporation of volatile oxides.

In this study, hydroxyapatite, titania, and HA-TiO 2 composite layers are deposited by suspension plasma spraying on titanium substrates and assessed by means of SEM and XRD analysis, Raman spectroscopy, and acoustic emission testing. The coatings exhibited dense microstructures with low porosity and good interfacial bond strength. The main phase in the HA and composite coatings was found to be similar to the peak of the feedstock powder. In the composite and titania coatings, besides rutile and anatase, a significant percentage of thermally stable Ti 3 O 5 was observed, which is favorable for photocatalytic performance.

In the High Velocity Oxygen Fuel (HVOF) technology, the coating properties are sensitive to the behaviors of in-flight particles, which are mainly influenced by the processing parameters. However, due to the complex chemical and thermodynamic reactions, the real-time optimization of the coating properties during the HVOF process is still a challenging issue. This study focused on establishing an Artificial Neural Networks (ANN) model to analyze the influence of the processing parameters on the characteristics of in-flight particles. Hydroxyapatite (HA) powders were selected to deposit onto the stainless steel substrates via an improved HVOF spraying system. Combined with an Accuraspray-g3 system applied to acquire the temperature and velocity of inflight HA particles, the artificial neural network algorithm was well trained to predict the velocity and temperature of in-flight particles. The relationship between the variations of the operating parameters (gas flow rates and fuel-to-oxygen ratio) and the behaviors of in-flight HA particles was investigated, which therefor contributes to analyzing and optimizing the mechanical performance and crystallinity of the HA coatings.

Magnesium light weight alloys are currently being studied as implants due to their biodegradability. However, its applications are limited by high rate hydrogen evolution during corrosion. Coating on this substrate is one of the ways to reduce the rate of corrosion and increase the life of this type of implant. Hence, hydroxyapatite (HA) was coated on the substrates by using high velocity oxy- fuel (HVOF) spraying. The main purpose of such coatings is increasing bioactivity as well as corrosion resistance of the Mg alloy. Crystal structure was characterized by X-ray diffraction (XRD). Crystallinity of the coating was about 70% in which HA is dominant phase. The amounts of hydrogen gas released during magnesium corrosion tests in simulated body fluid (SBF) were measured to evaluate the corrosion resistance of the coated samples. This coating could decrease hydrogen evolution from 100 per cm 2 .mL to about 15 per cm 2 .mL after 29h of immersion time.

Phase composition and microstructure of hydroxyapatite (HA) significantly affects the biological and mechanical properties of final hydroxyapatite (HA) coating. In the present study, HA coatings were deposited on Ti-6Al-4V by micro-plasma spraying (MPS) using different spray parameters. The influence of spray parameters on the composition and microstructure of the coatings were investigated. To understand the formation mechanism of HA coatings, the in-flight particles and splats were examined as well. The morphologies of coatings surface, cross-sections, initial powder, in-flight particles and splats were characterized by scanning electron microscopy (SEM). Xray diffraction (XRD) was employed to analyze the phase composition. Three typical HA coatings were fabricated. The results indicated that the coating composition and microstructure were tightly related to the melting state of inflight particles. And this was influenced by the spraying parameters. The formation mechanisms of these coatings were discussed.

Hydroxyapatite (HAP) is available in powder form for plasma spraying. HAP powder was fabricated indigenously in the Rod form of diameter 4.17mm. This rod was sprayed with the help of MEC make Rodojet 9810 (flame spray process). Rodojet parameter were optimised for HAP rod. Crystallinity and purity level of HAP rod was measured. XRD and SEM were used to analysed the microstructure of rod and coating. The microstructure, mechanical properties of the coating were investigated, and measure the Ca/P ratio of coating and rod. The micro-hardness and elastic modules were determined by indentation tests and bond strength was determined by tensile test. The results showed that the microstructure, mechanical properties was observed same as in plasma spray process. Porosity was observed more than 15%. The bond strength of coating was observed 20 MPa. Scratch test was done to measure the cohesive strength of coating. This new experiments play an important role for reduction the cost of the HAP powder coating.

In this study, hydroxyapatite (HA) and HA-SiO 2 coatings are applied to unalloyed Ti by atmospheric plasma spraying and corrosion resistance is assessed by immersion in Ringer’s solution for 24 h. The results show that the HA coating improves corrosion resistance, which is further improved with the addition of SiO 2 . An analysis based on Scherrer’s equation confirms an observed increase in crystallite size in the coated samples.

This work serves as a proof-of-concept for the application of plasma sprayed hydroxyapatite (HA) coatings on biopolymer implants. In the absence of a conventional plasma sprayer, coating samples were produced by manually injecting HA powder into a plasma cutting torch fitted with a custom made nozzle. Using the improvised setup, hydroxyapatite was successfully deposited on PLA, PEEK, and PVA discs as well as Al and Ti substrates. The coatings were characterized by thermal imaging and scanning electron microscopy, and the results are presented and discussed.

In this study, hydroxyapatite (HA) coatings were deposited on stainless steel by suspension plasma spraying. Coating samples and suspensions were examined by means of electron microscopy, XRD analysis, and FTIR and Raman spectroscopy. The results show that the coatings are porous and nanostructured with no impurity phases when low H 2 flow rates are used. They also contain a significant amount of OH - and CO 3 2- , which facilitates the formation of well-crystallized HA and improves bioactivity and compatibility in implant applications.

In this work, two agglomerated hydroxyapatite (HA) powders, with and without heat treatment, were cold sprayed using various spraying parameters on metallic (Ti-6Al-4V) and polymeric (PVA) substrates. The structure of the agglomerated powders and corresponding features of the coatings were examined. For both types of substrates, it was shown that submicron HA powders produce homogenous layers with submicron HA grains. In the case of non-heat treated particles, thick layers could be obtained due to the binding action of residual by-products. HA layers were also found to be adherent after immersion in water, which could potentially lead to the fabrication of ceramic coated hydrogels.

In this work, micro-plasma spraying is used to produce hydroxyapatite coatings on Ti-6Al-4V substrates. To understand coating formation mechanisms, in-flight particle velocity and surface temperature were monitored under different spraying conditions. XRD measurements show that the resulting coatings have a high degree of crystallinity with little amorphous or metastable phases. Some of the coatings were also found to have a uniformly distributed columnar structure, corresponding to a strong (002) texture and excellent stability in Hanks’ salt solution even after 14 days of immersion.

During suspension plasma spraying, the evaporation of liquid from the solution precursor alters the composition of the working gases thereby changing their thermal transport properties. This aim of this work is to better understand how aqueous calcium-phosphate, used in the synthesis of hydroxyapatite, affects thermal transport in Ar-H 2 plasma gas mixtures. Transport properties of the working gases were determined before and after injection of the precursor solution using T&TWinner, a free computational tool for thermochemistry. The results show that a significant increase occurs in the thermal conductivity of the Ar-H 2 gas mixture after the injection of the calcium-phosphate solution, but there is little change in momentum transfer between the working gases and solution droplets based on viscosity calculations. Although the software predicts an increase in the heating ability of the Ar-H 2 plasma jet, the absence of fully melted splats in the coatings suggests that it is not enough to melt HA particles.

In this study, bioactive glass powders were synthesized from four different types of oxides (SiO 2 , P 2 O 5 , CaO and MgO). These oxides were mixed, melted, milled and sieved to produce powders with two chemical compositions of the 31SiO 2 -11P 2 O 5 -(58-x)CaO-xMgO system. The powders were plasma sprayed onto AISI 316L stainless steel and Ti6Al4V titanium alloy substrates using a F4MB Sulzer Metco gun. The physical and mechanical properties of coatings, as well as their bioactivity were evaluated. The bioactivity tests were carried out exposing the surface of coatings to simulated body fluid (SBF) during 1, 9 and 15 days. The thickness and hardness of apatite layer produced on the surface of each coating during bioactivity tests were evaluated. The results indicate that the thickness of apatite layer formed during 15 days in SBF is between 31 and 51 µm and its hardness is between 1.5 and 1.9 GPa according to the chemical composition of feed stock powder used to manufacture the coatings. Additionally, the harness of bioglass coatings decreased around 26% after to expose them to SBF.