Composition, structure and microhardness of steel samples after induction nitriding were studied in the work. As a result of high-temperature nitriding, saturation of R6M5 steel with nitrogen was observed as its content in the surface layer changed from 4.19 to 7.3 at.%. The maximum surface microhardness of the samples was 1950±70 HV0.98. The possibility of the formation of strengthened diffusion layers up to 200 μm deep and having microhardness up to 1500±50 HV0.98 on R6M5 steel was established. The parameters of the depth of the diffusion layer and microhardness depended on the heating temperature of the specimens and the processing duration in the course of induction nitriding.
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.
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.
In the study, morphology, composition, and hardness of the coatings formed by electrospark alloying (ESA) of titanium with zirconium and subsequent induction heat treatment were considered. The possibility of forming coatings with a maximum size of oxide crystals of 8.9±3.8 μm and an open porosity reaching 58 % was established. The morphology parameters depend on the modes of electrospark alloying and heat treatment. There was a decrease in zirconium content in the coating composition from 21.9 to 1.1 at.% when the temperature and duration of induction treatment were increased. Maximum hardness equalled 10.3±0.3 GPa.
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.
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 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.
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.
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.
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