This study presents the results of modeling the process of chemical heat treatment (CHT) of titanium disk-shaped samples located in a container with a carbon-containing medium. The main parameters of the considered process were the inductor current and the geometry of the "inductor – container – sample" system, namely, the number of turns, the height and internal diameter of the inductor at constant values of the height and external diameter of the container for CHT. The operating temperature of the outer surface of the container varied in the range from 1100 °C to 1350 °C, which was achieved at an inductor current from 3.4 kA to 5.0 kA in a narrow frequency range of 88±2 kHz. The obtained plots of the distribution of temperature fields made it possible to assess the heating efficiency of inductors of various designs.
The results of a study of the dependences of the inductor current and heating kinetics on the power consumption value for titanium samples in the course of treatment with high frequency currents in the range from 88 to 120 kHz were presented. The effect of the inductor current in the range from 0.6 to 8.5 kA on the heating kinetics of equimass samples of disk and cylindrical shapes in the temperature range from 800 °C to 1700 °C in air was established. It was shown that the kinetics of a one- and two-cycle induction treatment had differences at the alpha-phase temperature.
This study presents experimental results of the investigation of the diffusion behavior of commercially pure titanium when interacting with oxygen and hydrogen. To study the gas absorption, electron microscopy combined with energy-dispersive analysis and secondary ion mass spectrometry were used. It was shown that in the course of heat treatment with high-frequency currents in the temperature range from 600 to 1200 °C, an intensive absorption of oxygen by the surface of titanium was observed. At the same time, desorption of hydrogen from the near-surface layer of titanium occurred and there was a double decrease in hydrogen concentration during thermal treatment in this temperature range.
In this paper, a review of the two- and multicomponent (Ti, Zr, Ta)-(O, C, N) phase diagrams was presented. The conditions of thermal effect on the studied refractory metals (Ti, Zr, Ta) in the presence of nonmetallic elements (O, C, N) for obtaining oxides, carbides and nitrides were determined. It was shown that in order to obtain refractory ceramic layers (coatings) of the required composition it was necessary to provide the heating above 1000 °C. For this purpose, the treatment with high-frequency currents of metal samples directly in a gaseous atmosphere or in a reaction chamber (container) containing a solid carbon-containing medium (cementing medium) was most effective.
Electrospark alloying (ESA) technology has existed for a long time (since the middle of the 20th century) but its potential has not been exhausted yet. In the present paper it is proposed to increase the mechanical properties of steel and titanium products by doping with a hard carbide alloy based on "WC-TiC-Co" system. As a result, the hardness of coatings obtained by ESA reaches at least 18-22 GPa with a layer thickness of up to 0.5 mm. The proposed solution can improve the functional qualities of various friction surfaces that are used in engineering, as well as in friction elements.
The treatment with high frequency currents (HFC) is traditionally used to improve the mechanical properties of metal products, in particular hardness and wear resistance. A new method of carburization of titanium samples in a solid carburizer using HFC is proposed in the work. The temperature of the carburization is characterized by a wide range from 1000 to 1400 °C. As a result of thermochemical treatment, a hard coating of TiC (H ≥ 20 GPa) with a microstructure (d = 7-14 μm) consisting of nanoparticles (d = 10-12 nm) is formed on the titanium surface. These coatings are widely used in friction pairs for various purposes, including machinery, instrumentation and medicine.
In the course of high-temperature treatment with high-frequency currents (HFC) in the range from 600 to 1300 °C, carbon and tool steels are strengthened. After the heat treatment the hardness reaches 64-70 HRC for carbon steel (carbon content 0.4-0.5%) and 68-71 HRC for tool steel 1.3343 (R6M5 steel analogue with 0.9-1.0% C content, W – 5-6 wt%, Mo – 3.5-5.3 wt%, V – 1.3-1.8 wt%, Cr – 3.8-4.3 wt%, Mn+Si – 0.5-1 wt%, Fe – balance). The resulting structure is a carbide network, and in the case of tool steel – complex carbides around a high-strength martensitic phase.
Research results on the chemical composition and surface morphological characteristics of zirconium products after machining and treatment with high-frequency currents are described. It was established that at the temperature range from 600 to 1200 °C and duration of heat treatment from 30 to 300 seconds oxide coatings consisting of nano-grains are formed.
The study focuses on high-performance combined electro-spark alloying of titanium and titanium alloy (VT1-0, VT16) surface and porous matrix structure oxidation. The metal-oxide coatings morphology is the result of melt drop transfer, heat treatment, and oxidation. The study establishes the influence of technological regimes of alloying and oxidation on morphological heterogeneity of biocompatible layered metal-oxide system Ti-Ta-(Ti,Ta)xOy. It was found that during electro-spark alloying the concentration of tantalum on the titanium surface ranges from 0.1 to 3.2 at.%. Morphology of the deposited splats is represented by uniformly grown crystals of titanium and tantalum oxides, which increase from nano- to submicron size.
Using scanning electron microscopy the crystalline structure of porous oxide coatings produced by air-thermal oxidation of orthopedic implants of alloy 12Cr18Ni9Ti at the temperatures of 350 and 400 °C and duration of 1.5 hours was studied. In vivo tests revealed that the resulting coatings promote successful engraftment of thermally modified implants in the body with highly efficient interaction between morphologically heterogeneous coatings and surrounding bone tissue.
Prospective composite bioceramic titania coatings were obtained on intraosseous implants fabricated from cp-titanium and medical titanium alloy VT16 (Ti-2.5Al-5Mo-5V). Consistency changes of morphological characteristics, mechanical properties and biocompatibility of experimental titanium implant coatings obtained by oxidation during induction heat treatment are defined. Technological recommendations for obtaining bioceramic coatings with extremely high strength on titanium items surface are given.
Production of biocompatible nano-ceramic coatings is one of the major goals in prospective materials technology, particularly, in biomedical items, e.g. intraosseous implants and joint endoprostheses. Ceramic coatings obtained by the existing methods do not have the required structural properties of biocompatibility, which causes quality reduction. It has been stated that thermal induction preheating of substrate ensures the required structural organization of hydroxyapatite coating, grain size and shape in particular.
Prospective composite bioceramic titania coatings were obtained on intraosseous implants fabricated from medical titanium alloy VT16 (Ti-2.5Al-5Mo-5V). Consistency changes of morphological characteristics, physico-mechanical properties and biocompatibility of experimental titanium implant coatings obtained by oxidation during induction heat treatment are defined. Technological recommendations for obtaining bioceramic coatings with extremely high strength on titanium items surface are given.
The article describes prospective composite biocompatible titania coatings modified with hydroxyapatite nanoparticles
and obtained on intraosseous implants fabricated from commercially pure titanium VT1-00. Consistency changes of
morphological characteristics, crystalline structure, physical and mechanical properties and biocompatibility of
experimental titanium implant coatings obtained by the combination of oxidation and surface modification with
hydroxyapatite during induction heat treatment are defined.
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