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|Tehnologie chimică. Industrii chimice și înrudite (840)|
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SILKIN, Serghei; AKSENOV, E.; LIKRIZON, E.; PETRENKO, Vladimir; DIKUSAR, Aleksandr. The increasing of heat-resistent chromium-nickel alloys high-rate anodic dissolution localization in electrolytes for electrochemical machining. In: Materials Science and Condensed Matter Physics. Ediția a 9-a, 25-28 septembrie 2018, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2018, p. 272.
|Materials Science and Condensed Matter Physics
Ediția a 9-a, 2018
Conferința "International Conference on Materials Science and Condensed Matter Physics" |
Chișinău, Moldova, 25-28 septembrie 2018
Heat-resistant Chromium-Nickel alloys are widely used to produce blades of gas turbine engines. For their manufacturing are used electrochemical machining (ECM). One of the main tasks of ECM is to improve the accuracy of copying the electrode-tool (ET). This achieved by increasing the localization of anodic dissolution. One of the main methods of increasing the localization is to create in the system a ET- machined surface of the increasing current efficiency dependence on the current density. This is usually achieved by using pulse machining modes . One of the variants of the pulse machining is to the use of nanosecond pulses range . In this case the growing dependence of current efficiency on the current density is due to the transition from the capacitive current to the Faraday current with increasing current density. The detection of such a relationship using the microsecond range of pulse duration greatly simplifies the technology. The report presents results of the study of high-rate pulse-galvanostatic anodic dissolution of heat-resistant alloys EI612 (% mass.) (Fe~ 43, Ni~33, Cr~16), EI617 and EI893 (Ni~66, Cr~15) in chloride, nitrate and chloride-nitrate electrolytes with the same conductivity (~0,15 Sm/m). Anodic dissolution was carried out until current densities 100 A/cm2 are using pulse current (PC)(pulse duration 20 μs, duty cycle 10-50%). We investigated the change of current efficiency (specific dissolution rate, mg/C) and surface roughness (Ra, μm) after dissolution on current density (PC, DC and average rate of treatment at different duty cycle PC).It was found that at anodic dissolution of EI617 and EI893 alloys the current efficiency dependence on the current density is absent in all electrolytes both with the use of a direct current and pulsed. When using the chloride electrolyte there is a weak dependence for EI612 alloy (steel) and only for impulse treatment with a duty cycle ~10%. For chloride-nitrate and nitrate electrolytes the dependence occurs for duty cycle 25-10%, but with increase of more than 25% it is not observed. A more pronounced dependence is observed for nitrate-chloride mixtures. Ra surfaces after machining reaches a minimum at i ˃ 30 A/cm2 (0,2-0,3 μm for a chloride-nitrate mixtures and 0,4-0,7 μm for nitrate electrolyte). Considering that the use of pulse regimes leads to a decrease in the average machining rate, it can be stated the optimal parameters of pulse machining for purpose of the increasing localization anodic dissolution of EI612 steel for pulse duration 20 μs are pulse current density 100 A/cm2 and duty cycle 25%. The average dissolution current density will be 25 A/cm2 and the average rate of machining with increasing localization is 0,36 mm/min. It is shown that the causes of current efficiency dependence on the current density for pulsed machining of the investigated steel are thermokinetic effects.