It is shown that the existing chromizing processes are characterized by a number of shortcomings. It is proposed to use the microarc thermochemical treatment technology to form a carbide coating on the material surface. Thermodynamic calculations on the reducing reactions of chromium oxide which is the diffusion source are made. It is revealed that the most probable reaction behavior is the chromium oxide reduction by methane and carbon with the formation of atomic chrome, and a consistent formation of Cr3C2, Cr7C3, and Cr23C6 carbides with an increase in temperature. The obtained results are checked through experiments. As a result of the hardening processing, a surface layer on the basis of chromium carbides with the depth of 20–25 microns is produced under which there is a carbonized area of eutectoid concentration, followed by a baseline ferrite-pearlitic structure.
microarc steelwork chromizing, formation of surface carbide coating, thermodynamic calculations of chemical reactions.
Введение. Одним из наиболее эффективных методов поверхностного упрочнения металлов и сплавов является химико-термическая обработка (ХТО). Она достаточно проста и может быть реализована на любом предприятии, имеющем термический цех или участок. Однако традиционные процессы ХТО (цементация, нитроцементация, азотирование) не всегда удовлетворяют современным требованиям, предъявляемым к деталям машин и инструменту. Это обусловливает интерес к процессам формирования диффузионных высокотвёрдых покрытий на основе карбидов, нитридов и боридов. Существующие технологии формирования таких покрытий отличаются большой продолжительностью, что сдерживает их практическое применение. Целью настоящей работы является изучение возможности интенсификации процесса формирования высокотвёрдых покрытий на основе карбидов хрома на поверхности стальных изделий.
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