The work investigated the effect of induction heat treatment (IHT) on the morphology of titanium coatings obtained by plasma spraying (PS). IHT of titanium samples was carried out at temperatures of 650±50 and 1200±50 °C and duration of 120 s. It was found that the porosity of the PS coating was 57±3 %. The average grain size was 9.57±0.2 μm, and the pore size was 13.01±0.5 μm. The thickness of the formed layers was 320±30 μm. Thermal modification at an inductor current of 2.6 kA led to an increase in the average grain size to 11.12±0.3 μm, the pore size remained practically unchanged and amounted to 12.40±0.4 μm, the surface porosity of the coating also did not change and remained equal to 58±5 %. The thickness of the modified layers decreased to 265±20 μm. With an increase in the inductor current to 8.0 kA, the average grain and pore size decreased to 8.95±0.2 and 8.12±0.2 μm, respectively. The porosity of the modified layer did not change and remained equal to 56±1%. After the modification process, the scale peeled off from the coating surface, which led to a decrease in the thickness to 197±25 μm. The study of adhesion strength by a qualitative method showed that this parameter increased after IHT.
Currently, there are various methods allowing the improvement of the physical and mechanical properties of metalworking tools. Gas nitriding is one of the given methods. In this work, the improvement of the physical and mechanical properties of high-speed tool steel products using induction chemical thermal treatment (ICTT) in a nitrogen-containing environment is proposed. As a result of the use of short-term treatment by the ICTT method, the hardness of the surface layer of products reaches at least 17–20 GPa with a layer thickness within 0.8 mm. The proposed method enables the improvement of the functional qualities of metalworking products operating under the conditions of friction with increased contact loads.
Combined materials having a high-strength and wear-resistant work surface are used in the material processing industry. To obtain materials, which can provide high wear resistance indicators, complex technological equipment is required. It is also possible to use materials having a hard base with a protective coating of wear-resistant high-hardness material. Therefore, a method of resistance welding for applying a coating of commercially pure titanium to the surface of highspeed 1.3343 tool steel (analogue of R6M5) and subsequent modification of the titanium surface and the entire assembly by high-temperature induction heating to obtain a wear-resistant oxide coating is considered in this work.
In this work, a numerical simulation of induction vacuum deposition of titanium on hardened steel samples was performed. The rational geometry of the tubular target and the induction heating modes, which ensure the minimum heating of the steel plate, were determined. The main results of simulation experimentally confirmed the possibility of creating conditions for the formation of titanium layers on the surfaces of steel plates.
The combined structures of a "tool steel – titanium – oxide" system are used in tool industry. For this purpose, the application of resistance welding, which is widely used in the automotive industry, can be considered quite promising. It is possible to improve the quality of a joint of this type due to induction treatment. Thus, in the current study, the results of simulation of the induction heat treatment of bimetallic products, the structure of which contains a bearing base of X91CrMoV18 chromium tool steel, a protective coating of titanium and a thin wear-resistant oxide layer, were shown.
The paper describes a new method for obtaining a permanent connection of titanium with tool steel and subsequent high-temperature treatment with high-frequency currents in the air. As a result of thermal treatment, a hard and wear-resistant layer of titanium dioxide was formed on titanium. The resulting metal oxide ceramic was tested as a coating for metalworking (cutting) tools. After the preliminary tests, the morphology of the wear of the cutting edges was studied and two wear variants were established – abrasion and shearing. The nature of wear depended on the heat treatment modes and the thickness of the solid layer.
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.
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.
In order to create highly efficient medical systems and measuring biosensors, an approach is frequently used, in which the constructive basis of the product is made of a high-strength biocompatible material (titanium, stainless steel), and the functional layer is made of a more expensive metal (Ta, Zr, Au, Pt, etc.) or ceramics (Ta2O5, ZrO2, CaTiO3, etc.). For a strong connection, e.g. titanium with tantalum, it is proposed to use diffusion butt welding. The heat generated by passing electric current (I is not less than 1.95-2.05 kA, P – not less than 9 kW, t = 250-1000 ms) and applied pressure (30-50 MPa) ensure an integral connection. To improve the quality of the joint, i.e. to exclude cracks and tightness, it is necessary to choose the right combination of the thickness of the welded parts. It was established that when titanium (2 mm thick) and tantalum (0.1-0.5 mm) are combined, a better Ti-Ta welded joint is formed when tantalum foil is used (0.5 mm). Here the distribution of hardness over the cross section of the sample, including the welding areas, is uniform and has no extremely high residual stresses of the tensile type.
As a result of heat treatment of titanium in the high-temperature range (1000-1200 °C), a layer of rutile (TiO2) is formed on the surface, the hardness of which can reach 60 GPa. The production of the coating includes an intensive growth of the crystals, spontaneous scale delamination (up to 100 μm thick) and formation of a submicrometric porous-crystalline structure of a superhard thin coating (about 0.5-1.5 μm thick). Preliminary tests have shown that the resulting coatings of the system "steel substrate – Ti+TiO2" can be used as tool coatings in the treatment of structural steel (0.4-0.5 wt.% carbon content), as well as chromium steel 40Cr13 (0.4 wt.% carbon content, chromium – about 13 wt.%) with a hardness within 45 HRC. These coatings are also characterized by biocompatibility, which was previously proved by in vitro and in vivo tests.
This work presents the results of studying the mitochondrial membrane potential, intracellular ROS, peculiarities of the cell cycle of cancer cells HCT-116 and the normal line of CHO cells when exposed to the red LED light with a wavelength range of 0.620-0.680 μm. A dose-dependent increase in mitochondrial membrane potential and intracellular ROS concentration in cancer cells HCT-116 was established. In normal CHO cell line a dose-dependent reduction of mitochondrial membrane potential and dose-dependent increase in intracellular ROS occur. It has been shown that the sensitivity of the studied cell lines to the red light depends on the stage of the cell cycle.
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.
The results of the study of morphological and biophysical parameters of the cell membrane of live lymphocytes in patients with insulin-dependent and non-insulin dependent diabetes mellitus and healthy donors using atomic force microscopy have been presented. It is found that lymphocytes from patients with diabetes are characterized by a decrease in volume and cell surface roughness compared to normal lymphocytes. An increase in the Young's modulus of lymphocytes in patients with diabetes more than 3 times compared to normal rates has been shown. Increased stiffening of lymphocyte cytolemma in patients with non-insulin dependent diabetes mellitus leads to a decrease in its adhesive properties, unlike lymphocytes in patients with insulin-dependent diabetes mellitus.
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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