Low-temperature plasma technique for skin structure consolidation

摘要

Durability indicators of products operating in extreme conditions largely depend on their working part material properties, the properties of the surface layer in particular. For the purposeful formation of these properties, the method of the surface layer exposure to a gas discharge of low-temperature plasma formed by the interaction of microwave electromagnetic and electrostatic fields has been developed directly around the product surface. As a result of this impact, a significantly harder structure may form in the surface layer due to consolidation of the surface layer material. The paper presents a study performed to answer the question about the mechanism that leads to the consolidation. The results showed that this mechanism is mostly related to local thermal effect on the surface layer that occurs due to the neutralization of negative ions, molecules, and molecular complexes formed in plasma. Ion formation depends on the appearance of slow electrons with energy of about 0-3.5 eV in the plasma. Maximum mechanism impact is achieved while ensuring a high rate of negative ion and molecule formation and attaining their maximum concentration on the surface. In this regard, to ensure the formation of negative ions and molecules, it is necessary, firstly, to select a technological mixture of gases in which plasma effects the surface so that it contains atoms and molecules that have high electron affinity, and secondly, to control the energy level of the microwave electromagnetic field. Practical implementation of these recommendations allowed the average 2.0-2.3-fold increase of the real product endurance.