V. I. Kalita

The shear strength of three-dimensional capillary-porous titanium coatings for intraosseous implants

A plasma spraying process for the deposition of three-dimensional capillary-porous titanium coatings using a wire has been developed. In this process, two additional dc arcs are discharged between plasmatron and both the wire and the substrate, resulting in additional activation of the substrate and the particles, particularly by increasing their temperature. The shear strength of the titanium coating with 46% porosity is 120.6 MPa. A new procedure for estimating the shear strength of porous coatings has been developed.

The influence of three-dimensional capillary-porous coatings on heat transfer at liquid boiling

The process of heat transfer at pool boiling of liquid (Freon R21) on tubes with three-dimensional plasma-deposited capillary-porous coatings of various thicknesses has been experimentally studied. Comparative analysis of experimental data showed that the heat transfer coefficient for a heater tube with a 500-μm-thick porous coating is more than twice as large as that in liquid boiling on an otherwise similar uncoated tube. At the same time, no intensification of heat exchange in the regime of bubble boiling is observed on a tube with a 100-μm-thick porous coating.

The Effect of Resistance Spot Welding on Plasma Sprayed Coatings

The processes of thermoplastic treatment of plasma sprayed coatings made of 10R6M5 high speed steel, Kh20N80 nichrome, FBKh6-2 cast iron, and WC-Co and TiC-NiMo cermets upon resistance spot welding are investigated. Consolidation and deformation (up to 56% in the center of the spot weld) of the coating materials, reduction of the number of structure defects within the boundaries between the sprayed particles, and an increase in the cohesive strength and microhardness of coatings (up to 2.5 times for the 10R6M5 high speed steel) are shown to occur upon welding.

Structure and shear strength of implants with plasma coatings

Four types of three-dimensional plasma capillary-porous titanium coatings for model intraosseous implants are developed. By means of pulsed microplasma oxidation in solutions or plasma spraying of powders, additional bioactive coatings on the basis of calcium phosphates are deposited on the Ti coating surface. Shear strength values of the interface between the implants coated and osseous block after 16 weeks of implantation are 4.25–4.81 MPa, while for implants with additional plasma hydroxyapatite coating it exceeds 6.19 MPa after 4 weeks of implantation.

Formation of Bulk Magnetically Soft Materials with Nano and Amorphous Structure Using Plasma Spraying

A technique for producing coatings with an amorphous and nanostructure using a plasmatron with a gas-dynamic nozzle is proposed. The effect of the technical parameters of plasma spraying on the structure and magnetic properties of amorphous coatings is investigated.

Experimental Study of Rewetting of a Superheated Plate with Structured Capillary-Porous Coating by Flowing Liquid Film

The experimental results on rewetting of the surface of a superheated vertical copper heater and a heater with a structured capillary-porous coating (applied by means of directed plasma spraying) by liquid nitrogen film are presented. It is shown that presence of the capillary-porous coating fundamentally influences the temperature variation and reduces the duration of overall plate cooling by more than three times. The high-speed videofilming of the transient processes was carried out and data on the character and structure of the rewetting front were obtained. Analysis of the synchronized measurements of the plate temperature and the high-speed video of transient processes shows that the higher cooling rate in the presence of structured capillary-porous coating is related to the development of intensive boiling in the rewetting front at sufficiently higher plate temperature.

Structure and mechanical properties of three-dimensional capillary-porous titanium coatings on intraosteal implants

We developed a process of plasma wire spraying of three-dimensional capillary porous titanium coatings for intraosteal implants with the use of two additional arc discharges between the plasma gun and the wire and between the plasma gun and the substrate. By raising the temperature of sprayed particles and activating the substrate, we enhanced the shear strength up to 120 MPa for a titanium coating having the porosity of 46%.

Hydroxyapatite-based coatings for intraosteal implants

Using the buy-to-fly ratio for sprayed material, we optimized the method of creating nanostructured plasma coatings based on hydroxyapatite. After plasma spraying, the coating contains 67–83% hydroxyapatite phase. We studied several case of hydrothermal treatment of coatings for the purpose of strengthening them and in order to increase the hydroxyapatite phase content. After hydrothermal treatment of the coating at 650°C, we achieved the value of hydroxyapatite content around 98%. The size of coherentscattering regions grew from 95 to 122 nm. We proved that, after the treatment, the shear strength of hydroxyapatite-based coatings in relation to the titanium substrate is 22.3 MPa.

Ultradisperse and nano structures in plasma coatings hardened by electromechanical treatment

For the example of PRFBKh6-2 alloy and P6M5 steel powders, the structure of plasma coatings after electromechanical treatment is investigated by scanning probe microscopy. After such treatment, ultradisperse and nano hardening phases are formed in the coating. These phases are formed by the decomposition of the coating’s initial fast-quenched structure in high-speed treatment. The formation of characteristic structural zones hardened by nanoparticles and ultradisperse particles is analyzed; the proportions of nanoparticles and ultradisperse particles are determined by the parameters of the sprayed powder and the conditions of plasma spraying and subsequent electromechanical treatment.

The shear strength of Ti–HA composite coatings for intraosseous implants

Plasma spraying of composite coatings is developed and investigated. Three-dimensional capillary porous titanium (3DCP Ti) coatings with a thickness of 1 mm are sprayed using a wire. Hydroxyapatite (HA) coatings with a thickness of 0.08–0.35 mm are sprayed on 3DCP Ti coatings at a temperature of 300–550°C. The joint between the coating and plastic is analyzed at shear. The plastic simulates bone tissue that grows into the coating surface. The heating of the 3DCP Ti coating to 550°С when the HA coating is being sprayed increases the shear strength of the coating with respect to the plastic to 9.8 MPa. Modeling approximations are proposed for the shear of the joint between the coating and the plastic.