Markelova, Olga Anatolyevna

Markelova O.A., Koshuro V.A., Osipova E.O., Fomin A.A.

Plasma spraying is used to prepare a silicon carbide (SiC) coating on a titanium alloy VT6 base. A coating is formed by superposition of molten particles up to 90 μm in size with rounded microparticles up to 10 μm in size secured on their surface. Coating microhardness is not uniform, there are areas with 1200–1500 HV and 450–700 HV, and wear resistance corresponds to the class KI7/1. Coatings exhibit hydrophilic properties. Surface roughness is Ra 2.68 μm.

Koshuro V., Osipova E., Markelova O., Fomina M., Zakharevich A., Pichkhidze S., Fomin A.

Porous titanium-containing coatings were formed on titanium samples by atmospheric plasma spraying. The resulting samples were subjected to induction heat treatment in an oxygen-containing (air) atmosphere at normal pressure and treatment temperature of 650–1250 °C. As a result of experimental studies, it was established that thermal modification allowed an increase in the oxygen content in the coatings from 49.6 ± 9.2 to 71.7 ± 1.1 at.%. The change in the elemental chemical composition was accompanied by the formation of titanium oxide coatings, the surface of which was distinguished by the presence of acicular crystals of titanium oxide (TiO), anatase, and rutile (TiO 2 ) with an average length of 150–200 nm and a width of about 50–100 nm. Induction heat treatment also led to an increase in the microhardness of titanium oxide coatings from 1530 ± 55 to 1825 ± 191 HV 0.98 and an increase in adhesive strength.

Markelova O., Taran V., Artamonov B., Pichkhidze S.

The features of the structural and morphological characteristics of the powder of barium-containing tricalcium phosphate and coatings obtained by the method of thermal spraying on its basis have been investigated by the methods of optical and scanning electron microscopy. The optimal modes of plasma spraying of coatings on the basis of the studied powder, which make it possible to form a coating with a uniform and regular structure, have been established.

Osipova E., Markelova O., Koshuro V., Fomin A.

The work investigated the effect of induction heat treatment (IHT) on the morphology of titanium coatings obtained by plasma spraying (PS). IHT of titanium samples was carried out at temperatures of 650±50 and 1200±50 °C and duration of 120 s. It was found that the porosity of the PS coating was 57±3 %. The average grain size was 9.57±0.2 μm, and the pore size was 13.01±0.5 μm. The thickness of the formed layers was 320±30 μm. Thermal modification at an inductor current of 2.6 kA led to an increase in the average grain size to 11.12±0.3 μm, the pore size remained practically unchanged and amounted to 12.40±0.4 μm, the surface porosity of the coating also did not change and remained equal to 58±5 %. The thickness of the modified layers decreased to 265±20 μm. With an increase in the inductor current to 8.0 kA, the average grain and pore size decreased to 8.95±0.2 and 8.12±0.2 μm, respectively. The porosity of the modified layer did not change and remained equal to 56±1%. After the modification process, the scale peeled off from the coating surface, which led to a decrease in the thickness to 197±25 μm. The study of adhesion strength by a qualitative method showed that this parameter increased after IHT.

Koshuro V., Osipova L., Markelova O., Fomina M., Fomin A.

Abstract In this work, we studied the depth and microhardness of the layers formed on titanium during laser processing in a graphite environment. The energy and duration of the laser pulse varied from 0.76 to 10.17 J and from 0.5 to 3 ms, respectively. As a result of processing, the formation of layers characterized by a depth of 8.3-800 μm and a microhardness of 9.68-28.01 GPa took place. Regression models are constructed that describe the effect of laser processing conditions on the indicated characteristics of the layers. It was found that the pulse energy had the greatest effect on the depth and microhardness of hardened titanium.

Osipova E.O., Markelova O.A., Koshuro V.A., Fomin A.A.

Abstract In this article the process of induction-thermal modification of titanium coatings formed by electroplasma spraying was considered. The influence of the inductor current on the temperature of processed samples was experimentally established. The research results showed that thermal treatment of the samples with titanium coatings at a temperature of 750–1200 °C and a duration of 300 s led to an increase in porosity from 56±2 to 61±1 % and in microhardness from 1035–1532 to 1825–1883 HV0,98, the sprayed layer thickness decreased from 320±30 to 114±15 μm as well. A change of nanoscale structural elements shape was also observed.

Markelova O., Koshuro V., Fomin A., Aman A., Palis S.

Abstract The work investigated the possibility of forming carbide coatings by electrospark alloying on steel products of complex shape. It has been established that electrospark alloying at an AC current of 1.0 to 4.5 A makes it possible to form coatings of hard carbide alloy VK6 and T15K6 characterized by microhardness up to 11.5 GPa and by hardness HRA 86.6 and 81.5 with the nitial hardness of the steel product HRA 80.3.

Markelova O., Taran V., Pichkhidze S.

Structural and morphological characteristics of plasma-sprayed coatings on a titanium base, using powders of zinc-, magnesium-containing calcium phosphates, were studied by optical and scanning electron microscopy. The coatings consist of deposited particles with a size of 50 - 150 μm. The particles form agglomerates of 200 μm or more. Using such modes of plasma spraying of powders of metal-containing calcium phosphates as: plasma arc current - 300-350 A, spraying distance - 50-100 mm, powder dispersion - up to 90 μm, transport gas consumption - 5-7 l / min, it is possible to form a uniform coating.

Markelova O.A., Pichkhidze S.Y.

The technology for synthesizing fluoromagnesium apatite powder and the plasma-spraying technology for forming a coating based on it are presented. The recommended conditions for forming a coating based on fluoromagnesium apatite powder with open porosity > 40%, adhesive strength 15 MPa, hardness 190 HB and wettability are: arc current 300 A, dispersity of titanium powder up to 150 μm, dispersity of fluoromagnesium apatite powder up to 90 μm, consumption of plasma gas 20 L/min, spraying distance of titanium powder up to 150 mm, and the spraying distance of fluoromagnesium apatite powder up to 50 mm.

Grishina I.P., Lyasnikova A.V., Markelova O.A., Dudareva O.A., Lyasnikov V.N.

We performed a complex experimental investigation of plasma bioceramic coatings based on strontiumsubstituted tricalcium phosphate powder obtained by using different technological modes of spraying. We establish the technological conditions of the process of deposition of the coatings guaranteeing the production of adhesion-resistant coatings with a well-developed microscopic surface topography and hydrophilic properties.

Lyasnikov V.N., Telegin S.V., Grishina I.P., Lyasnikova A.V., Markelova O.A., Dudareva O.A.

The article is concerned with mathematical modeling of the method of laser treatment of titanium surface by the finite-element method in the FlexPDE program to obtain a qualitative and quantitative picture of the heating process of the treated surface that consists of the temperature field on the surface and in the bulk

Grishina I.P., Telegin S.V., Lyasnikova A.V., Markelova O.A., Dudareva O.A.

We propose a combined technology for the modification of the surfaces of titanium implants by laser radiation followed by the plasma spraying of biocompatible coatings. We performed comprehensive investigations of the coatings with the use of SEM, optical microscopy, and other methods. The coatings obtained by using the proposed procedure are characterized by the high adhesive strength, structural uniformity, and a sufficiently high degree of hydrophily.

Telegin S.V., Lyasnikova A.V., Dudareva O.A., Grishina I.P., Markelova O.A., Lyasnikov V.N.

Abstract—The surface morphology of the VT1-00 titanium alloy after pulsed laser processing is studied. The morphology of the titanium surface layer is revealed to depend on the modes of the technological process of modification by means of laser radiation. The variation in the technological-process parameters, such as the voltage of the excitation lamp, the duration and repetition frequency of pulses, and their number in at irradiation spot, provided the possibility of controlling the thermal effect on the formation of submicrometric parameters for metal-ceramic films and coatings. The effect of the processing modes on the parameters of the surface morphology heterogeneity is established. The possibility of modifying the surface morphology for a certain specific task is shown.

Lyasnikova A.V., Dudareva O.A., Lyasnikov V.N., Grishina I.P., Markelova O.A.

The synthesized silver-substituted tricalcium phosphate powder has been studied by infrared spectroscopy and X-ray diffraction. The plasma deposition of coatings based on this powder has been described. The structural–morphological and physicochemical characteristics of the coatings have been examined, and their adhesion strength and degree of hydrophilicity have been determined.

Lyasnikova A.V., Markelova O.A., Dudareva O.A., Grishina I.P., Lyasnikov V.N.

The structure of the silver-substituted hydroxyapatite and tricalcium phosphate powders is confirmed by the methods of X-ray phase diffraction analysis and IR spectroscopy. Silver-substituted hydroxyapatite coatings consist of large particles of round shape and the presence of nanoparticles is also detected. The silver-substituted tricalcium phosphate coatings are formed by fine particles and nanoparticles are detected on the entire surface of the coating. Both types of coatings exhibit hydrophilic properties. The adhesion of silver-substituted tricalcium phosphate coatings is almost twice higher than the adhesion of silver-substituted hydroxyapatite powder coating. The obtained coatings are of interest as antimicrobial coatings for intraosseous dental and orthopaedic endoprostheses.

Fu Y., Wang R., Wang Z., Zheng B., Zhang L.

This study addresses the challenge of uneven surface quality on the concave and convex regions during the precision machining of titanium alloy thin-walled complex curved components. An electrostatic field-controlled liquid metal-abrasive flow polishing method is proposed, which is examined through both numerical simulations and experimental investigations. Initially, a material removal model for the liquid metal-abrasive flow under electrostatic field control is developed, with computational fluid dynamics (CFD) and discrete phase models employed for the numerical simulations. Subsequently, the motion characteristics of liquid metal droplets under varying amplitudes of alternating electric fields are experimentally observed within the processing channel. This serves to validate the effectiveness of the proposed method in enhancing surface quality uniformity across the concave and convex regions of titanium alloy thin-walled complex curved components. Our results demonstrate that by controlling the distribution of the electric field in regions with varying flow strengths, the roughness differences between the concave and convex surfaces of the workpiece are reduced to varying degrees. Specifically, in the experimental group subjected to a 24 V alternating electric field, the roughness difference is minimized to 58 nm, representing a 44% reduction compared to conventional abrasive flow polishing. These findings indicate that the proposed electrostatic field-controlled liquid metal-abrasive flow polishing method significantly enhances the uniformity of surface polishing on concave and convex areas of titanium alloy thin-walled complex curved components.

Palanisamy K., Gangolu S., Joseph M.A.

316L stainless steel (SS316L) coatings were deposited on a AZ80 magnesium alloy by HVOF thermal spraying to enhance its corrosion behavior. Coatings with low porosity (0.21 ± 0.013%) and high microhardness (367 ± 4 HV0.3) were obtained from the optimized operating parameters, including an oxygen flow rate of 257 lpm, spraying distance of 231 mm, LPG flow rate of 61 lpm, carrier gas flow rate of 16.50 lpm, and powder feed rate of 38 gpm. The heat treatment (350–550 °C, 5–10 h) study revealed that SS316L surface roughness (using a 3D optical profilometer) remained unaffected; while, AZ80 Mg alloy roughness increased strongly (179–1140%). Electrochemical studies revealed that the SS316L-coated samples exhibited consistent corrosion potential (− 0.28 to − 0.23 V) and minimal corrosion current (4.16 ± 0.0055–4.60 ± 0.012 μA/cm2) versus fluctuating potential (− 1.74 ± 0.0183 V to −1.38 ± 0.035 V) and higher corrosion currents (186 ± 6.63–620 ± 10.12 μA/cm2) of bare AZ80 magnesium alloy. The fluctuating behavior in the bare AZ80 Mg alloy was related to variations in the Mg17Al12 precipitates at higher heat treatment temperatures. Also, SEM and EDX analyses of post corrosion products confirmed the protective role of SS316L coatings.

Cherenda N., Bibik N., Uglov V., Grigoriev S., Vereschaka A., Astashynski V., Kuzmitski A.

Investigation of compression plasma flows impact on structure, phase, and elemental composition, as well as mechanical properties of Ti-6Al-4V titanium alloy with ZrN coating was carried out in this work. X-ray diffraction, scanning electron microscopy, energy dispersion X-ray analysis, samples weight measurements, microhardness and tribological tests were used as investigation techniques. The findings showed that plasma impact led to the formation of a composite surface layer based on titanium alloy containing inclusions of undissolved ZrN coating. Growth of the absorbed energy density resulted in a decrease of zirconium and nitrogen concentration in the surface layer due to erosion. Formation of solid solutions on the basis of α-Ti and β-Ti was found in the layer analyzed by X-ray diffraction. Presence of nitrogen in a vacuum chamber as plasma generating gas led to the formation of TiN on the surface. Plasma impact resulted in decrease of ZrN/Ti-6Al-4V system microhardness and decrease of friction coefficient (at specific treatment regimes).

Yu J., Zhang S.

Induction cladding is a promising surface technology that combines the advantages of surface coatings and induction heating. It is an energy-efficient, environment-friendly, and cost-effective method that facilitates the fabrication of coatings with controllable thicknesses and ensures metallurgical bonding between the coating and the substrate. Owing to the high power-conversion efficiency of helical coil, induction cladding is particularly adaptable for the application of coatings on long shafts and rod parts, which find widespread use in mining and energy machinery. This paper provides a comprehensive overview of the state-of-the-art methods in induction cladding. Herein we focus on its mechanisms, cladding process and parameters, commonly used materials, simulations, innovative induction cladding technologies, industrial applications, problems, and future developments in this field.

Meng Y., Yang Z., Shi Y., Liu X., Wang L., Zhang Q., Yao J.

Lukaviciute L., Ganceviciene R., Tsuru K., Ishikawa K., Yang J., Grigoraviciute I., Kareiva A.

Senopati G., Rashid R.A., Juliadmi D., Prastya M.E., Mori M., Yamanaka K., Kartika I., Palanisamy S.

Titanium and its alloys are highly desirable materials for biomedical metallic implants due to their superior specific strength, excellent corrosion resistance, and exceptional biocompatibility. Among these alloys, Ti6Al4V is widely used in practical biomedical applications because it offers an excellent combination of strength, fracture toughness, and corrosion resistance. However, recent research has revealed limitations in its biocompatibility attributed to the presence of toxic elements such as Al and V. In addition, it has been reported that Ti6Al4V is costly due to the addition of Vanadium and has the potential for post-implant inflammation. As a result, researchers have been investigating new biomedical beta-Ti alloys using biocompatible, affordable, and easily accessible beta-stabilizers like Mo, Fe, and Cu, to achieve similar performance as Ti6Al4V alloys. The present study aims to develop a novel biomedical alloy through the arc melting method, to obtain an implant material possessing low elastic moduli, biocompatibility, and antibacterial properties to mitigate the risk of post-implant inflammation. Microstructural analysis was conducted using microscopy and x-ray diffraction, while the mechanical properties were evaluated through micro vickers hardness testing machine and elastic moduli measurement utilizing the impulse excitation technique. Cytotoxicity assessment was performed using the (Cell Counting Kit-8) CCK-8 method, followed by an examination of the alloy's antibacterial properties using the point counting method. β-Ti single phase was obtained in this study with the addition of ≥1% Fe and ≥1% Cu. The Ti-8Mo-2Fe-2Cu alloy was found to have the lowest elastic moduli of 95 GPa. Electrochemical measurements show that the Ti-8Mo- xFe- yCu alloys have a lower corrosion current density of around 0.319–2.317 µA/cm2 compared to Ti6Al4V of 16.543 µA/cm2. The Ti-8Mo-1Fe-3Cu, Ti-8Mo-3Fe-1Cu, and Ti-8Mo-3Fe-3Cu alloys have comparable biocompatibility with Ti6Al4V with the viability of mesenchymal stem cells (MSCs) above 75% and have a positive antibacterial response. Ti-8Mo-3Fe-3Cu alloy demonstrates the most favorable blend of microstructure, mechanical attributes, corrosion resistance, cell viability, and antibacterial properties as an alternate biomaterial for implant applications.

Yu X., Jiang R., Gao Y., Li Y., Gong W., Li X., Lü W.

Aluminium alloy is a widely used lightweight alloy in automobile and rail vehicle components, especially in parts such as brake pads and wheels, which require high wear resistance. Herein, to improve the wear resistance of aluminium alloys, Al2O3–13%TiO2 (AT13) reinforced Ni-based composite coatings were prepared by plasma spraying on 6061 aluminium alloy. The impact of AT13 content and heat treatment on the microstructure and wear resistance of Ni-based alloy coatings was systematically investigated. From our analysis, it was demonstrated that, in comparison to the substrate, the average micro-hardness of the composite coating with 10 %AT13 increased by more than 11 times, with a high value of 1250.81 HV0.2. Moreover, the average friction coefficient and wear rate reduced by 66 % and four orders of magnitude, with low values of 0.17 and 8.99 × 10−7 mm3(N−1∙m−1), respectively, which indicated a significant enhancement in wear resistance. In addition, after heat treatment at 450 °C for 2 h, the micro-hardness of the composite coatings was improved, and the wear rate further decreased. This effect could be attributed to the encapsulation of the hard ceramic particles in the nickel-based alloy, which may suppress the dislocation motion in the composite coating. This study provides valuable insights into enhancing the wear resistance of metal-based alloy coatings with ceramic composite coatings.

Hamedani K.S., Yadi M., Esfahani H.

This study focuses on the role of residual stress in the tribological behavior of calcium-phosphate (CaP) coating on titanium (Ti) substrate. The CaP coating was applied using an integrated electrospinning and rapid heating and cooling (EMRHC) process. The residual stress over half and full done EMRHC process was measured by x-ray method. The substrate and coatings were characterized using a field emission scanning electron microscope equipped with the energy-dispersive spectroscope, Vicker's microhardness, atomic force microscopy, and x-ray diffractometer techniques. It was found that the preliminary hydroxyapatite on the Ti substrate was exchanged with α-TCP, CaO, TiO2, CaTiO3, and Ti5P3 over the EMRHC process. The results also showed that the tensile + 591 ± 89 and compressive − 189 ± 42 MPa residual stress remained on the surface over the half and full done EMRHC process, respectively. The hardness, Young module, and ultimate tensile strength of both samples were enhanced significantly by the EMRHC process. The tribology of samples was comprehensibly evaluated in a dry and simulated body fluid solution. The CaP coating prepared by the full-EMRHC process showed the lowest wear rates in comparison with the others due to the compressive residual stress. The coefficient of friction of CPTi coated by EMRHC was significantly reduced when exposed to the SBF solution. Our findings revealed that EMRHC is a promising method to fabricate the Ti implant with higher mechanical properties.

Gao R., Huang Y., Zhou X., Ma G., Jin G., Li T., Wang H., Liu M.

Challenging environments in aviation, automotive, electric power, and various industrial sectors are increasing industry and technological demands, resulting in machine damage and energy loss from friction and wear between interacting surfaces. Addressing this issue requires the development of new and advanced materials, processing techniques, and surface modification methods to enhance performance and reduce friction and wear. Plasma spraying technology is essential for material surface reinforcement and modification because of its low cost and stability. This paper reviews and summarizes the research progress on plasma spraying wear-resistant coating material systems and tribological mechanisms, covering the working process and principles of plasma spraying equipment. It also details wear-resistant coating material systems, including iron-based, nickel-based, copper-based, other metal materials, oxides, and monoxide ceramic materials. Furthermore, it addresses the wear-resistant and friction-reduction mechanisms of wear-resistant coatings, aiming to summarize the tribological strengthening mechanism concerning wear resistance and friction reduction. Moreover, this paper covers aspects such as powder design, sealing treatment, laser remelting, and other methods for regulating the wear resistance of coatings, examining their influence on the wear resistance of coatings in material design, spraying process, and post-spraying treatment. Plasma spraying wear-resistant coatings should be used along with doping modification and other methods to study the new spraying materials; furthermore, the optimization of the spraying process and post-treatment methods should be investigated to prepare a wear-resistant coating that meets the performance of the actual working conditions. At the same time, ultrahigh temperature wear-resistant coatings and super lubricating coatings are also future research priorities. In addition, when comparing plasma transfer arc spraying technology and plasma enhanced high-speed arc spraying technology with plasma non-transfer arc spraying technology, the jet temperature is higher, and the cost is lower; however, since the process is still in its infancy, the follow-up should be strengthened in this area of technical research. This paper provides a theoretical basis and reference for researching plasma spraying wear-resistant coatings in various fields.

Xiao B., Wang J., Yang H., Yang D., Da M., La T., Temuqile T.

Abstract The Mongolian medical silver needles often encounter issues of bending, fracturing, and blunting in clinical applications. Similarly, Mongolian warm needles can cause burns on patients due to inaccurate temperature control. In this study, we developed an Ag85Cu15 alloy specifically for acupuncture needles based on material preparation. By incorporating appropriate amounts of Mn and Ti elements, we were able to enhance the mechanical properties and biocompatibility of the acupuncture needles. Compared to commercially available silver needles, this alloy exhibited a significant increase in microhardness up to 210.2 Hv0.2 and an improved tensile strength of 880.2 MPa. Furthermore, we designed a thermoelectric effect-based temperature measurement model for precise control of the warm needle's temperature, enhancing the therapeutic effectiveness of the treatment.

Wang G., Zhu X., Liu L., Ullah R., Wang Z., Wang B.

The low hardness and poor wear resistance of Ti-6Al-4V titanium alloy limit its application. The laser cladding technology is widely used in material surface modification engineering. In this study, TiO2 layers were deposited on Ti-6Al-4V titanium alloy surface by coaxial laser powder cladding method with varying laser power (600 W, 800 W and 1000 W) and cladding times (1 and 2) to improve its surface mechanical properties. The mechanical properties of the original Ti-6Al-4V alloy substrate and clad samples were then investigated and compared. The microstructure formation mechanism of the TiO2 cladding layer was discussed. The results showed that the sample cladded two-times with a laser power of 800W has the highest value of microhardness (1583.2 HV0.1), nanoindentation (9.42 GPa), and Young's modulus (197 GPa) and lowest specific wear rate (1.42 × 10−2 mm3/Nm), which indicates excellent wear performance and surface hardness. The enhancement in the surface properties was attributed to both the dendritic structures that developed during the laser cladding process and the equiaxed crystals that were diffused in the interstices of coarse dendrites. The surface strength is significantly aided by reduced grain size and inter-grains spacing.

Al Khateeb S., Alley M.J., Beck J.P., Jeyapalina S., Sparks T.D.

The stability of fluorapatite (FAP) thin films, which is required for bone ingrowth in FAP-coated bioimplants, improves with crystallinity. To investigate the crystallinity evolution of FAP thin films, they are deposited on titanium and alumina substrates through ultrasonic spray pyrolysis using different deposition arrangements. Two different solutions of pre-synthesized homemade FAP powder and chemical precursors are used for film deposition at different deposition variables. The films are next post-deposition treated in different environments and temperatures up to 1200°C. X-ray diffraction and electron microscopy are employed to study the films' morphology and crystallinity. A thermodynamic simulation software is used to investigate the stability of different phases by the construction of the Ellingham diagram, possible side reactions, and phase decomposition. The study reveals that the high-temperature post-deposition heat treatments do not enhance film crystallinity and CaHPO4 and Ca3(PO4)2 phases are detected. Treatment in argon or evacuated ampoules leads to the formation of titanium oxides due to the substrate's reaction with H2O, a decomposition product of CaHPO4. Furthermore, the oxygen partial pressure employed during the annealing process in evacuated ampoules (1.3 × 10−3 Pa) exceeds the equilibrium value of 1.3 × 10−20 Pa, which promotes substrate oxidation. The use of alumina as a substrate does not improve crystallinity, possibly due to material loss during annealing. Overall, the as-spray-deposited FAP films have better film crystallinity than that achieved with other techniques.

García-Cadme R., García Cano I., Castaño O., Fernandez J.

Microbial colonization is one of the main causes of implant loosening and rejection. Pathogenic contamination and the subsequent biofilm formation reduce the implant’s chance of survival and can be life-threatening to a patient. Among the many strategies employed to reduce the infection probability of bioceramics, surface functionalization plays a key role. This chapter is dedicated to describing the different strategies available to prevent bacterial colonization and the proliferation of hydroxyapatite-coated implants. Moreover, the factors intervening in the bacteria-implant interaction will be described, detailing the mechanisms involved during the contact, adhesion, and proliferation of bacteria. Finally, the characterization methods will be discussed, emphasizing the bioactivity and antibacterial assays.

Al Khateeb S., Bennett B.T., Beck J.P., Jeyapalina S., Sparks T.D.

To correlate fluorapatite thin films’ morphology to their stability and bioactivity for temporary bioimplant applications, fluorapatite is ultrasonically spray-deposited on different substrates using chemical precursors. Mechanical agitation in phosphate-buffered saline solution is used to investigate the stability of the films aided with X-ray diffraction and electron microscopy for films’ morphology and thickness. For bioactivity, the cell adhesion to the fluorapatite thin films is evaluated by growing HaCaT cells on the film surface. The films deposited on titanium are pure and polycrystalline. Agitation in solution leads to a thickness reduction of 18.3%, and 30.5% for the films deposited on alumina. However, the persistence of the films after agitation suggests partial degradability. The improved stability of fluorapatite on titanium is attributed to the layer plus island-like morphology that offers a reduced contact area with the surrounding solution compared with the island-like morphology of fluorapatite on alumina. These different morphologies can be understood in the context of a smaller lattice mismatch between the substrate and the film which results in the layer plus island-like morphology. HaCaT cell adhesion on Ti-fluorapatite film surfaces is better than the titanium reference and alumina-fluorapatite suggesting its bioactivity and the promise of spray-deposited FAP for orthopedic applications.

Nikoomanzari E., Karbasi M., C.M.A. Melo W., Moris H., Babaei K., Giannakis S., Fattah-alhosseini A.

• The effect of critical implant pretreatment parameters are reviewed. • Nanoparticle addition and duplex treatment dominate antibacterial PEO coatings. • Bacteria-killing methods like contact, release, trap and photocatalysis are discussed. • Photocatalytic and release killing of PEO coatings investigation is extremely needed. Ti and Ti-alloys are widely utilized as suitable biomaterials for implants, since they present good biocompatibility and mechanical properties. However, they can be an ideal substrate for bacteria attachment, promoting biofilm infections. Biomaterial-associated infections is one of the major healthcare challenges that is currently faced by humanity. This fact causes increased morbidity and distress in patients, along with high economic costs due to increased hospitalizations. There are several strategies to overcome the biofilm infection associated to implants, especially plasma electrolytic oxidation (PEO) process. PEO is highly effective in the production of hard, porous, wear- and corrosion-resistant, as well as biocompatible coatings. Additionally, this method can be applied to introduce antibacterial coatings, with the most prevalent ones being bacteria-killing and bacteria-repelling. Thus, in this review, the biofilm formation implications in implants are presented, as well as the antibacterial mechanisms presently known. The effect of PEO on the antibacterial ability of Ti and Ti-alloys will then be discussed in detail. Finally, the PEO procedure parameters and modifications that lead to high performance of antibacterial implants will be presented.

Fiorillo L., Cicciù M., Tozum T.F., Saccucci M., Orlando C., Romano G.L., D’Amico C., Cervino G.

In recent years, implantology has made significant progress, as it has now become a safe and predictable practice. The development of new geometries, primary and secondary, of new surfaces and alloys, has made this possible. The purpose of this review is to analyze the different alloys present on the market, such as that in zirconia, and evaluate their clinical differences with those most commonly used, such as those in grade IV titanium. The review, conducted on major scientific databases such as Scopus, PubMed, Web of Science and MDPI yielded a startling number of 305 results. After the application of the filters and the evaluation of the results in the review, only 10 Randomized Clinical Trials (RCTs) were included. Multiple outcomes were considered, such as Marginal Bone Level (MBL), Bleeding on Probing (BoP), Survival Rate, Success Rate and parameters related to aesthetic and prosthetic factors. There are currently no statistically significant differences between the use of zirconia implants and titanium implants, neither for fixed prosthetic restorations nor for overdenture restorations. Only the cases reported complain about the rigidity and, therefore, the possibility of fracture of the zirconium. Certainly the continuous improvement in these materials will ensure that they could be used safely while maintaining their high aesthetic performance.

Mutter M.M., Jabbar R.H., Khudiar A.I.

Surface modification of dental implants is an important key process in the fabrication of these medical materials. In this paper, a novel method of aluminum-doped titanium oxide (TiO2: Al) thin films as a functional coating for resistance to adhesion bacteria in dental implantology by RF magnetron plasma sputtering technique is presented. The ratios of doping were (0, 2, 4, 6) % weight concentration. The characteristics of produced films have been studied by X-ray diffraction (XRD) for structural properties, atomic force microscopy (AFM) for surface morphology, and antibacterial tests. The results showed that the phase of TiO2 was anatase type and the crystal phase was tetragonal and the crystalline size increased from 21 to 26.27 nm with increasing of Al concentration; the image of AFM showed the roughness increased from 0.95 to 1.46 nm with increasing Al concentration except for Al (6%) concentration. The antimicrobial results showed good efficacy of the prepared thin films in resisting bacterial growth and the zone of bacterial growth inhibition reach 21 mm.

Cubero Á., Martínez E., de la Fuente G.F., Cano I.G., Dosta S., Angurel L.A.

• Plasma spraying and subsequent laser remelting to improve alumina coatings on copper. • Optimization of the laser processing to minimize the size and impact of microcracks. • Optimized alumina coatings on copper as heat sinks with electrical insulations. • Large enhancement of cryogenic thermal conductance of these Cu/alumina/Cu joints. Joints of high thermal contact conductance and electrical insulation have been obtained by coating copper supports with thin alumina (Al 2 O 3 ) layers (of 140–150 μm thickness). This has been achieved by a combination of plasma spraying process and the subsequent coating remelting by a near-Infrared (n-IR) laser. With a proper optimization of the laser processing conditions, it is possible to transform the metastable γ-Al 2 O 3 phase of the as-sprayed coatings to stable α-Al 2 O 3 , and to achieve denser alumina coatings. This results in a large enhancement of the thermal conductance of the joints, enabling their application as heat sinks at cryogenic and ambient temperatures. The process proposed in this work is scalable for the formation of alumina coatings on large metallic pieces of complex geometries.

Bai L., Chen P., Zhao Y., Hang R., Yao X., Tang B., Liu C., Xiao Y., Hang R.

Osseointegration is a sophisticated bone and implant healing process comprising of initial hematoma formation, immediate osteoimmunomodulation, angiogenesis , and osteogenesis. To fulfill rapid and satisfying osseointegration, this study developed a biomimetic implant coating that could confer the intraosseous implants a systematical regulation of the participatory processes. Herein, we shaped dissimilar nano-scale (NS) to form highly biomimetic structures of natural extracellular matrix (ECM) of the host bone and bone healing hematoma with micro/nano-scale (MNS) titania fiber-like network on the surface of titanium (Ti) implants. In vitro experiments revealed that the MNS not only facilitated osteogenic and angiogenic differentiation of bone marrow stromal cells (BMSCs) and endothelial cells, respectively, but also suppressed M1 macrophages (MΦs), whereas, stimulated pro-healing M2 phenotype. Notably, BMSCs on MNS surfaces enabled a significant immunomodulatory effect on MΦs resulting in the downregulation of inflammation-related cell signaling pathways. The favorable osteoimmune microenvironment manipulated by MNS further facilitated osteo-/angio-genesis via the crosstalk of multi-signaling pathways. In vivo evaluation mirrored the aforementioned results, and depicted that MNS induced ameliorative osseointegration when compared with the NS as well as the pristine Ti implant. The study demonstrated the modulatory effect of the multifaceted biomimetic structure on spatiotemporal regulation of the participatory processes during osseointegration. • A micro/nanoscale coating on titanium is highly biomimetic to the native bone hierarchical structure thus accelerating osseointegration. • A micro/nano-biomimetic coating can induce BMSC osteogenic differentiation and polarize MΦs to pro-healing M2 phenotype. • The study unveils the impact of micro/nano structures on the cellular interactions and the interplay of cell signaling pathways.

Ossowska A., Olive J., Zieliński A., Wojtowicz A.

• The nanotube layer is formed on the gas oxidation layers created on the titanium alloy. • The nanotubular structure is strongly dependent on previous gas oxidation. • The colonies of nanotubes of different lengths are observed. • The duplex layer demonstrates good corrosion resistance and biological properties. The research focuses on the development and characterization of innovative thin hybrid oxide coatings obtained in subsequent processes of thermal (TO) and electrochemical (EO) oxidation. Four different surface modifications were investigated and the microstructure was determined, the mechanical, chemical and biological properties of the Ti-13Nb-13Zr alloy were assessed using scanning electron microscopy, X-ray dispersion analysis, glow discharge emission spectroscopy, Raman spectroscopy, nanoindentation and corrosion resistance measurements. The composite layers were evaluated for antimicrobial activity, cytotoxicity bioassays and wettability tests were performed. The conducted studies of two-stage oxidation (TO + EO) have shown that it is possible to obtain layers with a different structure - crystalline and nanotubular. The formation of a nanotube layer on the surface of the crystalline layer is dependent on the thickness of the crystalline layer. The produced double titanium oxide coatings show high surface roughness, high corrosion resistance, are hydrophilic, slightly antibacterial, and not cytotoxic, which has a huge impact on the process of connecting the tissue with the implant.

Rothammer B., Neusser K., Marian M., Bartz M., Krauß S., Böhm T., Thiele S., Merle B., Detsch R., Wartzack S.

Diamond-like carbon (DLC) coatings have the potential to reduce implant wear and thus to contribute to avoiding premature failure and increase service life of total knee replacements (TKAs). This two-part study addresses the development of such coatings for ultrahigh molecular weight polyethylene (UHMWPE) tibial inlays as well as cobalt–chromium–molybdenum (CoCr) and titanium (Ti64) alloy femoral components. While a detailed characterization of the tribological behavior is the subject of part II, part I focusses on the deposition of pure (a‑C:H) and tungsten-doped hydrogen-containing amorphous carbon coatings (a‑C:H:W) and the detailed characterization of their chemical, cytological, mechanical and adhesion behavior. The coatings are fabricated by physical vapor deposition (PVD) and display typical DLC morphology and composition, as verified by focused ion beam scanning electron microscopy and Raman spectroscopy. Their roughness is higher than that of the plain substrates. Initial screening with contact angle and surface tension as well as in vitro testing by indirect and direct application indicate favorable cytocompatibility. The DLC coatings feature excellent mechanical properties with a substantial enhancement of indentation hardness and elastic modulus ratios. The adhesion of the coatings as determined in modified scratch tests can be considered as sufficient for the use in TKAs.

Sokolov V.N., Chernov M.S., Kalita V.I., Komlev D.I., Radyuk A.A.

Porous coatings are actively used in engineering practice. The porous coating determines the reliability of the operation of the intraosseous implant and the heat transfer process when the aggregate state of the refrigerant is changed. The choice of method for quantitative analysis of porosity is determined by the structure of the coating. In this study, plasma coatings sprayed from powders were analyzed. A porosity of 10.3% inside the alumina coating was analyzed by mercury porosimetry. The main volume of the porosity of the coating is formed by pores ranging in size from 0.13 to 0.36 μm; their share in the total volume is 68.29%. The remaining volume is distributed in sizes of 0.04–0.12 mm, 0.58–4.66 mm, and 5.66–18.2 mm. Microtomography makes it possible to get a more complete general idea of the macro- and microstructure of coatings, establishing the mechanisms of its formation, and to obtain data on the real shape of the pores. A quantitative description of the visible pores of three-dimensional capillary-porous 3CaO⋅Al2O3 coatings in the form of ridges and depressions was determined by raster image analysis using special STIMAN programs. The porosity of this coating is 39.7% of the distribution over four pore groups: 0.74–3.56, 4.34–11.57, 14.08–55.65, 67.73–267.71 mm.

Markelova O.A., Pichkhidze S.Y.

The technology for synthesizing fluoromagnesium apatite powder and the plasma-spraying technology for forming a coating based on it are presented. The recommended conditions for forming a coating based on fluoromagnesium apatite powder with open porosity > 40%, adhesive strength 15 MPa, hardness 190 HB and wettability are: arc current 300 A, dispersity of titanium powder up to 150 μm, dispersity of fluoromagnesium apatite powder up to 90 μm, consumption of plasma gas 20 L/min, spraying distance of titanium powder up to 150 mm, and the spraying distance of fluoromagnesium apatite powder up to 50 mm.

Shah A., Fasehah S.N., Hassan M.A., Daud R., Che Kob C.G.

Abstract This work aims to study the effect of mechanical treatment technique on titanium coated with PVD for the enhancement of corrosion resistance for the biomedical implant. First, substrates were coated with TiN via PVD then applied the mechanical treatment through ultrasonic vibration. Results show that all coated samples treated with ultrasonic vibration improve the surface of the coated sample and produce a compact coating as compared with a substrate coated without mechanical treatment. The corrosion test evaluated by Potentiodynamic polarization and Electrochemical Impedance Spectroscopy indicated that all coated samples treated with mechanical treatment showed high corrosion resistance as compared with the untreated sample. It can be concluded that mechanical treatment which is a simple technic can be used as an alternative to improve the corrosion resistance thus reduce the implant and manufacturing cost for biomedical applications.

Gerasimenko A.Y., Kurilova U.E., Savelyev M.S., Murashko D.T., Glukhova O.E.

A laser technology has been developed for fabricating structures from composite layers based on biopolymers: albumin, collagen, and chitosan with single-walled carbon nanotubes (SWCNT). The structures are intended for cardiovascular devices and tissue-engineered implants. This is evidenced by the results of studies. The composite layers were fabricated due to the phase transition of biopolymers and SWCNT aqueous dispersion under the influence of laser pulses. At the same time branched 3D networks of SWCNT were formed in the biopolymer matrix. The threshold energy fluence of laser pulses was determined (0.032–0.083 J/cm2) at which a bimodal distribution of pores was observed. The calculation of contact resistances between nanotubes at percolation units of 3D networks (20–100 kOhm) was carried out. Composite layers fabricated by laser demonstrated conductivity values that were higher (12.4 S/m) than those for layers by thermostat (4.7 S/m). The maximum hardness of the composite layers with SWCNT (0.01 wt%) by laser was 482 ± 10, 425 ± 10, and 407 ± 15 MPa for albumin, collagen and chitosan, respectively. The hardness of the thermostat layers was less than 100 MPa. The viability of endothelial cells in composite layers was improved. The composite layers ensured a normal level of hemolysis during interaction with erythrocytes.

Krysina O.V., Prokopenko N.A., Ivanov Y.F., Tolkachev O.S., Shugurov V.V., Petrikova E.A.

Multi-layered gradient (Zr,Nb)N coatings were deposited with vacuum-arc evaporation of pure Zr and Nb metal cathodes. The gradient of the Nb concentration through the thickness was obtained by varying the arc discharge current with a Nb cathode within 80–150 A under the constant pressure of a working Ar/N 2 gas mixture and a constant current of arc discharge with a Zr cathode. These coatings were studied by scanning and transmission electron microscopes, X-ray diffraction analysis, micro- and nanoindentation, and tribological measurements. The synthesized coatings show a high hardness, relatively low Young's modulus, relatively high H / E ratio, a high degree of elastic recovery, low surface roughness, a low friction coefficient, and a low wear rate. These coatings also feature a multiphase and multi-layered nanocrystalline structure with alternation of only layers with higher and lower Nb concentration. • (Zr,Nb)N coatings with gradient of Nb concentration through the thickness are deposited by the vacuum-arc deposition. • The physical, mechanical, and tribological properties;the structure, phase and elemental composition are presented. • A gradientcoating features a multiphase nanocrystalline structure and improved properties compared to a homogeneous coating. • Multi-layered gradient (Zr,Nb)N coatings possess high hardness, wear resistance, high H/E ratio, and elastic recovery

Pachimalla P.R., Mishra S.K., Chowdhary R.

Hydrophilic implant surface has gained increasing interest as a factor to stimulate osseointegration.The study was done to formulate hydrophilic gel to be applied on to the dental implant surface, to enhance bone to implant contact (BIC).In first part of study, Acemannan and Moringa oleifera hydro gel formulated in different proportions were coated on the titanium disk and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay was done to evaluate cell viability.Cytotoxicity of aqueous extracts of two plants were tested against UMR106 cells. In second part of study, the prototype titanium implants were placed in tibia and femur of 8 male rabbits. Hydrophilic gel formulated from Acemannan and Moringa oleifera were coated on the study groups of implants. Histomorphometric analysis was carried out of the enbloc sections specimens. Student's unpaired t-test was used to compare mean values between the two groups.The alkaline phosphatase assay showed least cell inhibition for Acemannan and Moringa oleifera (2:1) as 4.45% and osteoblastic differentiation as 0.328 at 540 nm. Titamium disc coated with hydrogel of Acemannan and Moringa oliefera and seeded with Human MSC shows increased proliferation of osteoblast cells.Compare to study group implants, control group showed no new bone formation.Hydrophilic implant surface showed new bone formation with increased bone to implant contact.There was absent of degenerative changes, necrotic changes, fibrosis, and inflammation at the new BIC.

Grishina I.P., Lyasnikova A.V., Markelova O.A., Dudareva O.A., Lyasnikov V.N.

We performed a complex experimental investigation of plasma bioceramic coatings based on strontiumsubstituted tricalcium phosphate powder obtained by using different technological modes of spraying. We establish the technological conditions of the process of deposition of the coatings guaranteeing the production of adhesion-resistant coatings with a well-developed microscopic surface topography and hydrophilic properties.

Song S.H., Min B.K., Hong M., Kwon T.

Titanium nitride (TiN) was deposited on the surface of a cobalt–chromium (Co–Cr) alloy by a hot-wall type chemical vapor deposition (CVD) reactor at 850 °C, and the coating characteristics were compared with those of a physical vapor deposition (PVD) TiN coating deposited on the same alloy at 450 °C. Neither coating showed any reactions at the interface. The face-centered cubic (fcc) structure of the alloy was changed into a hexagonal close-packed (hcp) phase, and recrystallization occurred over at 10 μm of depth from the surface after CVD coating. Characteristic precipitates were also generated incrementally depending on the depth, unlike the precipitates in the matrix of the as-cast alloy. On the other hand, the microstructure and phase of the PVD-coated alloy did not change. Depth-dependent nano-hardness measurements showed a greater increase in hardness in the recrystallization zone of the CVD-coated alloy than in the bulk center of the alloy. The CVD coating showed superior adhesion to the PVD coating in the progressive scratch test. The as-cast, PVD-coated, and CVD-coated alloys all showed negative cytotoxicity. Within the limitations of this study, CVD TiN coating to biomedical Co–Cr alloy may be considered a promising alternative to PVD technique.