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In recent years, many different biomedical implants have been created for prolonged usage within the human body. The number of these implants has been steadily expanding. It is a common practice to use metallic bioimplants as substitutes when attempting to replace human body components in an anatomically acceptable manner. But the metallic bioimplant was mostly made biocompatible by putting a biocompatible coating on its surface and then using the right surface modification techniques. This was the primary method by which the biocompatibility of the bioimplant was achieved. Thermal spraying is a method that is frequently employed in surface modification treatments to modify metallic bioimplants. These methods can be found in the medical field. This is due to the adaptability of the thermal spraying method. Because of their capacity to respond and adapt to physiochemical circumstances, coatings that are based on hydroxyapatite (HAp) are the most popular type to be used in thermal spraying. This is due to the fact that HAp is a naturally occurring mineral. On the other hand, the majority of the HAp coatings are unsuccessful as a result of the coating’s weak mechanical qualities and insufficient adhesive strength. Supplying the coating in question with reinforcement in the form of hard particles and doing so in the appropriate proportions makes it feasible to alter the qualities of HAp-based coatings to fulfill a variety of requirements. This can be accomplished by providing the coating with reinforcement. The purpose of this inquiry was to deconstruct and analyze a variety of thermally sprayed (TS) coatings. These coatings were used to adhere HAp-based coatings on bioimplants. In addition, a detailed discussion is offered on how the reinforcements have an effect on the mechanical and biocompatible qualities of the coatings. In addition, we have discussed the difficulties associated with TS HAp coatings and their potential uses in the manufacturing of 3D biomedical implants through the utilization of cold spray (CS).

This study aims at investigating the wear behavior of thermally sprayed Ni-based self-flux alloy coatings against different counterparts. Ni-based self-flux alloy powders were flame-sprayed onto a carbon steel substrate and then heat-treated at temperature of 1000 °C. Dry sliding wear tests were performed using the sliding speeds of 0.2 and 0.8 m/s and the applied loads of 5 and 20 N. AISI 52100, Al₂O₃, Si₃N₄ and ZrO₂ balls were used as counterpart materials. Wear behavior of Ni-based self-flux alloy coatings against different counterparts were studied using a scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that wear behavior of Ni-based self-flux alloy coatings were much influenced by counterpart materials.

Thermal spray coating method has been known to be an attractive technique due to its relatively high coating speed. However, a high corrosion resistance of the coating film deposited by thermal spray method should be improved to prolong its lifetime. In this study, four types of coated films (DFT: 400 μm), that is, pure zinc, pure aluminum and two Al – Zn alloy (Al:Zn = 85:15 and Al:Zn = 95:5) films were coated onto a carbon steel (SS401) with arc spraying, and the corrosion behaviors of these samples were investigated using the electrochemical method. The pure aluminum sample had the best corrosion resistance in seawater solution and alloy (Al:Zn = 85:15) film, so called galvalume followed the pure aluminum sample, moreover, the alloy (Al:Zn = 95:5) sample exhibited the worst corrosion resistance.

Metallic bioimplant are widely used now-a-days to replace a part of human body in a physiologically accepted manner. However, the bio-compatibility of the metallic bioimplant was mainly achieved by the incorporation of a bio-compatible coating on its surface through suitable surface modifications techniques. In surface modifications techniques, the thermal spraying is widely used for modification of metallic bioimplant due to its versatile nature. In thermal spraying, the hydroxyapatite (HAp)-based coatings are mainly preferred because this coating responses to physiochemical environment and adapts itself accordingly. But bulk of the HAp coating give out due to less adhesion strength of the HAp coating and its poor mechanical properties. The properties of HAp-based coatings can be designed as per requirements by reinforcing this coating through hard particulates in suitable proportions. In this paper, the various thermal sprayed (TS) coatings used for performing HAp-based coatings on bioimplant were discussed. The influence of reinforcements on the mechanical and bio-compatible properties of the coatings is also discussed in detail. Lastly, the challenges in the TS HAp coatings along-with the future perspective of TS coating in fabricating of 3D biomedical implants by using cold spray (CS) has also been summarized.

Among advanced ceramics, aluminum nitride (AlN) had attracted much attention in the field of electrical and structural applications due to its outstanding properties. However, it is difficult to fabricate AlN coating by conventional thermal spray processes directly. Due to the thermal decomposition of feedstock AlN powder during spraying without a stable melting phase (which is required for deposition in thermal spray). Reactive plasma spraying (RPS) has been considered as a promising technology for in-situ formation of AlN thermally sprayed coatings. In this study the possibility of fabrication of AlN coating by reactive plasma nitriding of alumina (Al₂O₃) powder using N₂/H₂ plasma was investigated. It was possible to fabricate a cubic-AlN (c-AlN) based coating and the fabricated coating consists of c-AlN, α-Al₂O₃, Al₅O₆N and γ-Al₂O₃. It was difficult to understand the nitriding process from the fabricated coatings. Therefore, the Al₂O₃ powders were sprayed and collected in water. The microstructure observation of the collected powder and its cross section indicate that the reaction started from the surface. Thus, the sprayed particles were melted and reacted in high temperature reactive plasma and formed aluminum oxynitride which has cubic structure and easily nitride to c-AlN. During the coatings process the particles collide, flatten, and rapidly solidified on a substrate surface. The rapid solidification on the substrate surface due to the high quenching rate of the plasma flame prevents AlN crystal growth to form the hexagonal phase. Therefore, it was possible to fabricate c-AlN/Al₂O₃ based coatings through reactive plasma nitriding reaction of Al₂O₃ powder in thermal spray.

Metallic bioimplant are widely used now-a-days to replace a part of human body in a physiologically accepted manner. However, the bio-compatibility of the metallic bioimplant was mainly achieved by the incorporation of a bio-compatible coating on its surface through suitable surface modifications techniques. In surface modifications techniques, the thermal spraying is widely used for modification of metallic bioimplant due to its versatile nature. In thermal spraying, the hydroxyapatite (HAp)-based coatings are mainly preferred because this coating responses to physiochemical environment and adapts itself accordingly. But bulk of the HAp coating give out due to less adhesion strength of the HAp coating and its poor mechanical properties. The properties of HAp-based coatings can be designed as per requirements by reinforcing this coating through hard particulates in suitable proportions. In this paper, the various thermal sprayed (TS) coatings used for performing HAp-based coatings on bioimplant were discussed. The influence of reinforcements on the mechanical and bio-compatible properties of the coatings is also discussed in detail. Lastly, the challenges in the TS HAp coatings along-with the future perspective of TS coating in fabricating of 3D biomedical implants by using cold spray (CS) has also been summarized.