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.
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.
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.
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.
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.
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