Abstract
Ion-plasma saturation with interstitial atoms (nitrogen or carbon) is a promising method for enhancing the surface strength and wear resistance of austenitic stainless steel parts and products. The paper considers the influence of method and temperature of ion-plasma treatment (IPT) on phase composition, thickness, and strength properties (microhardness) of the surface layers in 01H17N13M3 austenitic stainless steel specimens. Steel specimens with a coarse-grained structure were nitrided in the arc and glow discharge plasma at different temperatures (400 °C, 550 °C, and 700 °C). Regardless of temperature and IPT-method, ion-plasma nitriding leads to the formation of hardened surface layers in steel specimens. In this case, the thickness and phase composition of IPT-hardened layers depend on both the method and temperature of nitriding. Nitrogen saturation of specimen surfaces in the glow discharge at a temperature of 400 °C promotes the formation of a thin S-phase layer (nitrogen-expanded austenite, 4 μm in thickness). At the same IPT temperature in the arc discharge plasma, the authors observed the formation of a heterophase (Fe-γN, Fe4N, CrN, and Fe-α) surface layer with a significantly greater thickness (40–45 μm). Regardless of the IPT-method, a saturation of specimens at temperatures of 550 °C and 700 °C is accompanied by the formation of thick heterophase hardened layers (40–60 μm). In this case, the IPT method has a negligible effect on the phase composition of layers but significantly affects the ratio of the volume content of the hardened phases. After being IPT-processed in different modes, the microhardness distribution profile for all specimens has three typical zones: a composite layer (or S-phase at the IPT in a glow discharge at Ta=400 °C), a diffusion zone, and a matrix. With an increase in the saturation temperature, the thickness of the transition diffusion zone increases regardless of the IPT method.
Highlights
Profiles of microhardness distribution in depth of hardened layers in the FeCrNiMoC steel specimens ion-plasma treatment (IPT)-treated in the glow (a, b, c) and arc (d, e, f) discharges at the temperatures of 400 (a, d), 550 (b, e), and 700 °С (c, f) незначительно увеличивается по сравнению с протяженностью диффузионной зоны для образца, модифицированного в плазме дугового разряда при 400 °С
Solid carbon active screen plasma nitrocarburizing of AISI 316L stainless steel: Influence of N2-H2 gas composition on structure and properties of expanded austenite // Surface and Coatings Technology
Summary
Материалом исследования была выбрана стабильная аустенитная нержавеющая сталь (АНС) марки 01Х17Н13М3 (Fe-17Cr-13Ni-1,7Mn-2,7Mo-0,5Si-0,01С, масс. %). ИПО стальных образцов в тлеющем разряде осуществлялась на модернизированной установке ЭЛУ-5. Для очищения и активации поверхности образцов АНС на протяжении 20 мин было проведено катодное распыление в среде аргона при напряжении 1 кВ. После ионного распыления производился напуск рабочего газа – смеси азота и водорода N2(70 %)+H2(30 %). После ИПО образцы в течение 1 ч охлаждались в вакуумной камере. Образцы после насыщения были механически отшлифованы, отполированы и электрохимически протравлены в 10%-м водном растворе щавелевой кислоты. Металлографический анализ поверхностей образцов в поперечном сечении проводили на световом микроскопе Altami MET 1C. Рентгенофазовый анализ образцов до и после ИПО проводился на дифрактометре ДРОН-7 с Co-Kα излучением. Профили распределения микротвердости по глубине в поперечном сечении ИПО-образцов измеряли методом Виккерса (Duramin 5) с нагрузкой на индентор 50 г
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