The sphere of application of bimetallic materials is very extensive: oil and gas complex, nuclear energy, coinage, utensils, etc.
Bimetals are produced by a wide range of methods: galvanic, gas-thermal spraying, surfacing and others.
Bimetall is called a composite material, inWhich one metal, usually cheaper, is covered by another, more expensive with better performance. If the amount of metals in the composite is 3, then it is called trimetal. A composition of more metals is not used.
Application of bimetals
Anticorrosion coatings. Wherever corrosion-resistant metal is to be coated, copper, nickel, silver or other coatings with superior performance properties are used. Such a bimetal is actively used for the manufacture of corrosion-resistant equipment for oil and gas and nuclear power equipment, chemical utensils, kitchen utensils and clad coins.
Thermosensitive elements. Selecting a metal with different coefficients of thermal expansion can achieve obtaining a bimetal, which will deform towards the metal with a smaller coefficient of thermal expansion.
Antifriction coatings. Such a bimetal will be both cheap and resistant to abrasion.
Methods of manufacturing bimetals
Galvanic. When electricity passes through the solution, Faraday processes occur, for example, metal precipitates. Selecting a certain composition of the electrolyte, the temperature of the solution, the composition of the solution, achieve precipitation on the surface of the metal coating with the desired properties. For example, the simplest electrolyte for the deposition of a brilliant copper coating should contain copper sulfate, sulfuric acid and gelatin. The process is carried out at room temperature with a current strength of 1-5 A / dm2.
Gas thermal spraying. The metal is transferred to a dispersed state and is fed to the substrate on which the gas or plasma stream is condensed.
Surfacing by electric or plasma heating.
Immersion in the melt.
Explosive welding. Two rolled metal sheets are placed in parallel. On the one hand, a controlled explosion is carried out, which brings two sheets into close contact. Welding occurs due to simultaneous deformation.
Disadvantages of bimetals
The main disadvantage of bimetals isElectrochemical corrosion, which occurs at the ends, where both metals are simultaneously accessible to the environment. But, if the electrode potential of the coating is less than that of the base metal, the coating also provides protector protection.