Creation of Bioceramic Coatings on the Surface of Ti–6Al–4V Alloy by Plasma Electrolytic Oxidation Followed by Gas Detonation Spraying

Abstract

In this work, bioceramic coatings were formed on Ti6Al4V titanium alloy using a combined technique of plasma electrolytic oxidation followed by gas detonation spraying of calcium phosphate ceramics, based on hydroxyapatite. Plasma electrolytic oxidation was carried out in electrolytes with various chemical compositions, and the effect of electrolytes on the macro and microstructure, pore size and phase composition of coatings was estimated. Three types of electrolytes based on sodium compounds were used: phosphate, hydroxide, and silicate. Plasma electrolytic oxidation of the Ti–6Al–4V titanium alloy was carried out at a fixed DC voltage (270 V) for 5 min. The sample morphology and phase composition were studied with a scanning electron microscope and an X-ray diffractometer. According to the results, the most homogeneous structure with lower porousness and many crystalline anatase phases was obtained in the coating prepared in the silicate-based electrolyte. A hydroxyapatite layer was obtained on the surface of the oxide layer using detonation spraying. It was determined that the appearance of α-tricalcium phosphate phases is characteristic for detonation spraying of hydroxyapatite, but the hydroxyapatite phase is retained in the coating composition. Raman spectroscopy results indicate that hydroxyapatite is the main phase in the coatings.

Microplasma spraying of hydroxyapatite coatings on additive manufacturing titanium implants with trabecular structures

“…It can be emphasized here that Ohki et al [34] also noted the absence of harmful CaO compound in HA coatings obtained by thermal spraying. Moreover, Rakhadilov and Baizhan [35] note the presence of characteristic sharp HA peaks on the HA coating diffraction patterns, along with the absence of CaO, which demonstrates good crystallinity of the HA phase of the coating obtained by gas detonation spraying of HA powder on the surface of Ti-6Al-4V alloy. Results of the authors' previous scientific study [26] showed the same results as in this study for the values of purity and crystallinity of the microplasmasprayed HA coating on a pure titanium sublayer.…”

Btaining of Calcium-Phosphate Coatings on the Titanium Surface by Micro-Arc Oxidation

“…High porosity is observed in all samples. The presence of pores is favorable for the ingrowth of bone tissue in them and the formation of a stronger connection of the implant with the bone [4]. In order to confirm and coordinate the obtained optical microscopy data, it is necessary to additionally conduct scanning electron microscopy studies and X-ray spectral analysis, the results of which are planned to be published by the authors in the following papers.…”

“…The MAO method in aqueous solutions of electrolytes has become widespread in the last decade as a method of applying bioactive CF coatings to the surface of titanium [4]. The coating formation in a microarc discharge is associated with the course of high-temperature chemical processes in the zone of local micro-plasma and micro-arc discharges under the influence of an external high voltage source and is associated with the oxidation of the base material, as well as the transition of the ultrafine phase in the electrolyte into the coating.…”

Obtaining functional-gradient Ti-HA coatings by detonation spraying

“…During detonation combustion of a mixture of gases, propane and oxygen, the powder particles are affected by elevated temperatures, pressures and acceleration. The calculated temperature in the channel reaches 3000 K and the pressure is 5 MPa [22,23]. At the beginning of the process, the gas powder cloud reaches a velocity of 1500 m/s, and then slightly melted powder particles are moved to the substrate at a velocity of up to 1000 m/s.…”