Purpose: the development relates to the field of metallurgy, namely to chemical and thermal treatment and can be used for the manufacture of diffusion-hardened copper parts with increased durability during operation at high temperatures and corrosion wear.
Main characteristics: the development is aimed at obtaining heat-resistant thermal diffusion layers on copper and copper alloys. Copper and its alloys are often used in the manufacture of heat-trapping elements of technological equipment: crystallizers and tuyeres of metallurgical production, various cooling devices of the chemical industry, glass-making under-filter refrigerators, etc., which are operated under conditions of exposure to high temperatures and aggressive media in the form of vapors and substances that cause active corrosion of the surface of products. Having high thermal conductivity, copper has low heat resistance and corrosion resistance in some environments, in particular, it is rapidly destroyed by the action of sulfur and its compounds.
There are currently quite a lot of ways to protect copper and copper alloys, all of them are aimed at creating a barrier layer on the surface of the product. However, they are quite expensive, for example, Ni–P electroplating coatings, in addition to the characteristic obvious high cost on products of complex geometric shape, are implemented with great difficulty. The most rational way to protect against high-temperature oxidation and corrosion of copper is thermal diffusion saturation with elements that form dense, stable oxide layers during oxidation. Therefore, in the presented development, hardening is implemented through complex saturation from a mixture of a special composition, mainly aluminum.
Traditional alitized layers effectively protect the base metal from the penetration of oxygen and other substances, since at elevated temperatures aluminum oxide or spinel is formed on the surface, which has improved protective properties than CuO and CuO2. However, the use of developed compositions of mixtures for complex saturation allows to increase the durability and manufacturability of the process. Aluminum – boron-containing saturating mixtures allow saturation at lower temperatures and provide higher resistance of the thermodiffusion protective layer.
The diffusion layer, as a rule, includes three zones: a solid solution with a thickness of about 5...10 microns closer to the surface, a complex of aluminide phases deeper, these are solid solutions based on Cu3Al and Cu9Al4 compounds with a total thickness of 35...40 microns, as well as a transition zone (up to 8% Al wt.), which is α-a phase with a thickness of 10... 20 microns. After the subsequent oxidation process after saturation, the Al2O3 phase is also detected on the surface by X-ray diffraction analysis, as a result of the interaction of the already formed diffusion layer with air oxygen.
Economic viability: the developed complex technologies and saturating media for powder saturation from aluminum-boron-containing mixtures do not contain scarce and environmentally unsafe components, the mixtures are characterized by a low cost of 5-8 USD / kg, which is 2-3 times cheaper than foreign analogues. The hardening process is implemented on standard thermal equipment (shaft furnaces), with the presence of such equipment in production, capital costs are minimal.
Developer: Dashkevich V.G., PhD in Engineering
Contacts: tel. +375 (17) 293 96 85, e-mail: ontim@bntu.by
Main characteristics: the development is aimed at obtaining heat-resistant thermal diffusion layers on copper and copper alloys. Copper and its alloys are often used in the manufacture of heat-trapping elements of technological equipment: crystallizers and tuyeres of metallurgical production, various cooling devices of the chemical industry, glass-making under-filter refrigerators, etc., which are operated under conditions of exposure to high temperatures and aggressive media in the form of vapors and substances that cause active corrosion of the surface of products. Having high thermal conductivity, copper has low heat resistance and corrosion resistance in some environments, in particular, it is rapidly destroyed by the action of sulfur and its compounds.
There are currently quite a lot of ways to protect copper and copper alloys, all of them are aimed at creating a barrier layer on the surface of the product. However, they are quite expensive, for example, Ni–P electroplating coatings, in addition to the characteristic obvious high cost on products of complex geometric shape, are implemented with great difficulty. The most rational way to protect against high-temperature oxidation and corrosion of copper is thermal diffusion saturation with elements that form dense, stable oxide layers during oxidation. Therefore, in the presented development, hardening is implemented through complex saturation from a mixture of a special composition, mainly aluminum.
Traditional alitized layers effectively protect the base metal from the penetration of oxygen and other substances, since at elevated temperatures aluminum oxide or spinel is formed on the surface, which has improved protective properties than CuO and CuO2. However, the use of developed compositions of mixtures for complex saturation allows to increase the durability and manufacturability of the process. Aluminum – boron-containing saturating mixtures allow saturation at lower temperatures and provide higher resistance of the thermodiffusion protective layer.
The diffusion layer, as a rule, includes three zones: a solid solution with a thickness of about 5...10 microns closer to the surface, a complex of aluminide phases deeper, these are solid solutions based on Cu3Al and Cu9Al4 compounds with a total thickness of 35...40 microns, as well as a transition zone (up to 8% Al wt.), which is α-a phase with a thickness of 10... 20 microns. After the subsequent oxidation process after saturation, the Al2O3 phase is also detected on the surface by X-ray diffraction analysis, as a result of the interaction of the already formed diffusion layer with air oxygen.
Economic viability: the developed complex technologies and saturating media for powder saturation from aluminum-boron-containing mixtures do not contain scarce and environmentally unsafe components, the mixtures are characterized by a low cost of 5-8 USD / kg, which is 2-3 times cheaper than foreign analogues. The hardening process is implemented on standard thermal equipment (shaft furnaces), with the presence of such equipment in production, capital costs are minimal.
Developer: Dashkevich V.G., PhD in Engineering
Contacts: tel. +375 (17) 293 96 85, e-mail: ontim@bntu.by