Abstract
The problem of crack strength and wear resistance of metal products increase becomes particular significance in relation to continuously increasing requirement to their reliability and long service time. Traditional methods of volume strengthening of structure elements mainly exhausted their capacity. At the same time their resource, for example, under high wear conditions, is determined mainly by the structure and working surface properties and can be increased by application of plasma surface strengthening of metal products. Plasma surface strengthening of metal products is a typical of a technology covering spheres of plasma physics, hydrodynamics, theory of heat exchange, metal science. Complication of its mathematical simulation and digital calculation is stipulated by extensiveness of processes taking place: from crystal lattice scale till plasma treatment facility scale. By this reason experimental approach to solving a series of particular problems, enabling for optimizing plasma treatment facilities and technological process in the whole is important and actual. Results of influence study of outlet channel configuration of plasma treatment facility and treatment regimes on the structure and properties of metal surface after plasma thermal treatment presented. Forms of flow transformer outlet channel of plasmatron determined, providing the samples obtained demonstrated the highest level of surface hardness and wear resistance, during dry friction tests and wear test by semi-fixed abrasive material. It was shown, that change of the plasma treatment facility outlet channel configuration enables to effectively control the technological parameters (plasmatron travelling speed, plasmatron power and plasma-forming gas consumption), as well as the thermal cycle, which provides forming of required surface properties of treated detail. A basis of the results obtained based on the analysis of strengthened layer metal structure presented. Abrasion tests by a semi-fixed abrasive material showed, that surface plasma treatment gives a considerable wear resistance growth – up to 3 times comparing with a non-strengthened metal.
Highlights
Forms of flow transformer outlet channel of plasmatron determined, providing the samples obtained demonstrated the highest level of surface hardness and wear resistance, during dry friction tests and wear test by semi-fixed abrasive material
That change of the plasma treatment facility outlet channel configuration enables to effectively control the technological parameters, as well as the thermal cycle, which provides forming of required surface properties of treated detail
A basis of the results obtained based on the analysis of strengthened layer metal structure presented
Summary
При металлографическом исследовании упрочненного слоя образцов, обработанных по исследованным режимам, выявлено несколько основных типов микроструктуры. 84 БЮЛЛЕТЕНЬ «ЧЕРНАЯ МЕТАЛЛУРГИЯ» 12 2018 тенденции изменения микроструктуры по глубине слоя. За исключением режимов обработки No 1 и 2 в обратном направлении для всех исследованных режимов в поверхностных слоях присутствует низкоотпущенный пакетный мартенсит (600 НV0,981), который плавно переходит в промежуточный слой с неоднородной микроструктурой, состоящей из участков троостомартенсита (430 НV0,981). Еще глубже наблюдаются промежуточная микроструктура троостосорбита (330 НV0,981) и основной металл из сорбита отпуска с расположенными по границам зерен участками феррита (305 НV0,981). Режимы упрочнения оказали влияние на глубину слоев, различающихся структурным состоянием МИКРОСТРУКТУРА ПЛАЗМЕННО-УПРОЧНЕННОГО СЛОЯ, МАКСИМАЛЬНАЯ ГЛУБИНА ЗТВ И МИКРОТВЕРДОСТЬ НА ГЛУБИНЕ 0,05 мм ПРИ ОБРАБОТКЕ В ПРЯМОМ И ОБРАТНОМ НАПРАВЛЕНИЯХ
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