Optimization of Hydroxyapatite Synthesis and Microplasma Spraying of Porous Coatings Onto Titanium Implants

Abstract

The paper presents the main results of development and optimization of the synthesis of hydroxyapatite and the application of the micro-plasma spraying technique for biocompatible coatings. The hydroxyapatite synthesis was optimized using the mathematical modelling method. Synthesized hydroxyapatite was studied by IR spectrometry and X-ray diffraction analysis for assessment of the compatibility of the chemical and phase composition to the bone tissue. The Ca/P ratio of the obtained hydroxyapatite was 1.65, which is close to that of bone tissue (1.67). To increase the adhesion strength of the HA coating to the surface of the titanium implant, it was suggested to apply a titanium sublayer to the implant surface. Microplasma spraying (MPS) of biocompatible coatings from titanium wires and synthesized HA powders onto substrates made of medical titanium alloy has been carried out. Microplasmatron MPN-004 is used to obtain the two-layer coatings for titanium implants. The two layer coating includes a sub-layer of a porous titanium coating with a thickness in range from 200 up to 300 μm and the porosity level of about 30%, and an upper layer of HA about 100 μm thick with 95% level of HA phases and 93% level of crystallinity. The pore size varies from 20 to 100 μm in both coatings. The paper describes the technology and modes of microplasma deposition of two-layer coatings, including the mode of gas-abrasive treatment of the surface of implants made of titanium alloy before spraying. The synthesized HA powder and the Ti/HA coatings were investigated by optical microscopy and scanning electron microscopy with the energy dispersion analysis and the X-ray diffraction analysis.

The Application of Transmission Electron Microscopy to the Analysis of Powder Coatings Deposited on Metal Substrates by Plasma Method

“…The results of XRD and SEM analysis of HA powder and porosity of HA plasma sprayed coatings are presented in our paper [19]. At the current stage of research, the results of the TEM analysis of HA powder (Fig.…”

Fabrication and Characterization of Zr Microplasma Sprayed Coatings for Medical Applications

“…Before MPS, for the substrate surface activation [28], the substrate surface was subjected to gas abrasive blasting treatment followed by cleaning. The gas abrasive surface treatment was carried out by a Contracor ECO abrasive blasting machine (Comprag Group GmbH, Germany) using normal grade A14 electrocorundum at a compressed air pressure of 0.6 MPa, for further information refer to our paper [22].…”

“…The use of robotic MPS allows for precision coating deposition on complex-shaped implant parts, such as parts of elbow and hip replacements. In our previous papers [18][19][20][21][22], it was shown that robotic microplasma spraying can produce coatings on medical implants made of biocompatible titanium and hydroxyapatite materials with the desired porosity and roughness, meeting the requirements of international standards for implants for surgery in terms of coating adhesive strength [23], crystallinity and purity [24].…”

Pitting Corrosion behaviour of Austenitic Stainless-Steel Coated on Ti6Al4V Alloy in Chloride Solutions

“…The main two reasons which have attracted the researchers and manufacturers to use this type of Ti alloy are their biocompatibility with human tissue and having a modulus of elasticity that is close to that of bones. Thus, the alloy has been used for orthopedics, bone implant, hip prosthesis, dental implants, surgical screws [5][6][7][8].…”