MODEL OF ELECTROEROSION DESTRUCTION OF COMPOSITE ELECTROEXPLOSIVE COATINGS IN THE CONDITIONS OF SPARK EROSION

In this paper, the authors propose a model of electroerosion destruction of composite electroexplosive coatings of W – Cu, Mo – Cu, W – Cu – Cu, Mo – Cu – Cu, Ti – B – Cu, and TiB₂ – Cu systems underspark erosion that occurs when electrical contacts are opened. The model is associated with the evaporation of electrodes under the influence of heat flow, which arises from sparking when electrical contacts are opened. In constructing this model, the resistance of electrical contacts during the tests was in the range from 40 to 50  μΩ. The model was constructed in the framework of the problem of heating a half-space by a surface normal pulsed heat source uniformly distributed over an area of a certain radius and with certain duration of action. Distribution of the pulse energy in time was approximated by a rectangular pulse. The heat equation was solved in a cylindrical coordinate system for a plane instantaneous source with allowance for a finite time of the pulse. The vapor pressure of the metal was determined from the surface temperature. The calculations were carried out at a voltage of 380  V, a current of 3  A, a spark discharge time of 150  μs and a radius of the contact spot of a spark discharge with a surface of 152  μm. As a result, there were determined: the surface temperature of electrodes from pure metal, the surface temperature of electrodes from composite coatings, the depth of the evaporation layer of electrodes from pure materials, the loss of mass of the composite coating after a single discharge pulse, the relative change in the volumetric electroerosion resistance of electrodes from pure materials, durability of electrodes from pure materials, relative change in volumetric erosion resistance of electroexplosive composite coatings and the relative change in mass spark resistance of electroexplosive composite coatings. The partial composition of the elements­ included in the composite coating was calculated. The obtained results are in good agreement with the experimental results, especially in the W – C – Cu, Mo – C – Cu and Ti – B – Cu ternary systems. Comparison with data from the literature has a fairly good degree of correlation. Deviations for the binary W – Cu, Mo – Cu systems have causes in the model approximations.

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