Ultrasonic Intensification of Low-Temperature Plasma Synthesis of Ceramic-Like Coatings of Valve Metals
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Journal of Engineering Physics and Thermophysics, Vol. 93, No. 4, July, 2020
TRANSFER PROCESSES IN LOW-TEMPERATURE PLASMA ULTRASONIC INTENSIFICATION OF LOW-TEMPERATURE PLASMA SYNTHESIS OF CERAMIC-LIKE COATINGS OF VALVE METALS N. M. Chigrinova and V. E. Chigrinov
UDC 629.621.432.691.9.048.4
The authors have presented a method of ultrasonic intensification of anode–cathode interactions during the formation, in water–alkali electrolytes, of ceramic-like coatings on the surface of valve metals in the process of lowtemperature plasma synthesis. An algorithm of directional influence of high-energy fields on the distinctive features and rate of chemical reactions at the electrolyte–metal–coating interface through changing the solution′s state by ultrasonic pulses in the process of anodic microarc oxidation has been developed. The authors have elucidated the mechanism and have determined the character and level of effect of the proposed intensification on the dynamics of growth of a coating under low-temperature-plasma conditions of a liquid medium. It has been shown that mechanical (ultrasonic) activation of the electrolyte is responsible for the intensification of the process of transfer of charge carriers, which are primarily electrolyte ions. Procedures and equipment have been described using which the values of an ultrasonic signal formed under various conditions were recorded. The nature of more intense buildup in the thickness of a ceramic-like coating with reduced energy expenditure to form it has been elucidated. This is explained by the appearance in the electrolyte, during its ultrasonic activation, of the great number of high-frequency damped oscillations of irregular waveform with a high amplitude as far as the current is concerned (5 A or higher), which is attributable to the occurrence of a synergetic effect. Keywords: ultrasonic intensification, high-frequency damped oscillations of irregular waveform, oscillograms, sweep. Introduction. The development of the principles of control over the state of a material and over the change in its rheological characteristics in the process of anodic microarc oxidation (AMAO) and the creation of an algorithm of directional effect on the properties of coatings formed is based on studying the influence of various parameters of the process on the dynamics and kinetics of interaction at the electrolyte–base–coating interface, and also on analyzing thermal and mechanical stresses acting on the material. Such investigation results in optimizing the level of energy influence, the schemes of change in the contact surface in a tracking mode, the properties of the transfer medium, and the structural state of the coating. Various methods to control the process of anodic microarc oxidation, including changing the electrolyte′s state, are employed for directional microplasma synthesis of films of assigned chemical composition and crystalline structure on the anode during the oxidation [1]. One variant to reduce energy expenditure in forming oxide coatings in the process of anodic
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