Abstract
One of the main issues of austenitic stainless steel is low strength properties and low wear-resistance. It can be partially or fully eliminated by the product surface modification and the creation of hardened surface layers. The ion-plasma saturation of alloys with interstitials, which is carried out in a mixture of gases with different compositions is an available and effective method of surface hardening of complex structural parts. At the same time, the mechanical and plastic characteristics of the processed materials are determined by the complex of properties of the base alloy and the hardened surface, and it is not always possible to identify their influence on the mechanical and plastic properties of each component of the composite material. The nanoindentation method allows determining local mechanical and plastic characteristics in certain areas of hardened materials (base alloy and surface) by the dynamic loading of the local microscopic areas. In this paper, using the nanoindentation method, the authors identified the mechanical and plastic characteristics of hardened layers produced by the ion-plasma treatment of austenitic 01H17N13M3 stainless steel with the grain-subgrain and coarse-grain structures. The ion-plasma treatment of steel specimens facilitates surface hardening and the formation of a composite surface layer of ≈20-25 μm in thickness. High values of nano-hardness in a composite layer are caused by the complex hardening of specimens: solid-solution hardening of austenite with nitrogen and carbon, the dispersion hardening and the formation of different nitrides and carbonitrides and the ferrite low fraction. The experimental results show that the strength properties and plasticity characteristics of such a layer strongly depend on the base material initial microstructure - the formation of a highly-defective grain-subgrain structure promotes the formation of a more enforced surface layer compared to the coarse-grained specimens.
Highlights
plastic characteristics of the processed materials are determined by the complex of properties
plastic characteristics of hardened layers produced by the ion-plasma treatment
High values of nano-hardness in a composite layer are caused by the complex hardening of specimens
Summary
В качестве объекта исследования была выбрана стабильная аустенитная сталь 01Х17Н13М3 (Fe-16,8Cr-13,3 Ni-2,7Mo-1,7Mn-0,6Si-0,01C мас. %). изображены профили распределения нанотвердости по глубине в композиционном слое, диффузионной зоне и матрице образцов после ИПО. Для ТМО-2 образцов значения поверхностной нанотвердости в упрочненном слое ниже, чем в ТМО-1 образцах. Значения нанотвердости в диффузионной зоне не такие высокие, как в упрочненном композиционном слое, но они выше, чем в базовых ТМО-1 и ТМО-2 образцах представлены диаграммы нагружения ТМО-1 и ТМО-2 образцов аустенитной нержавеющей стали после ИПО в зависимости от расстояния до обрабатываемой поверхности. 3. Профили распределения нанотвердости и пластических характеристик в композиционном слое, диффузионной зоне и матрице ТМО-1 и ТМО-2 образцов аустенитной стали после ИПО. Показатели нанотвердости в области диффузионной зоны для образцов с зеренно-субзеренной структурой выше, чем для образцов с крупнозернистой структурой из-за различий в исходной микроструктуре и величине плотности деформационных дефектов (включая границы и субграницы), которые сохраняются после ИПО. При наноиндентировании материалов с помощью индентора Виккерса [15; 16]: H
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