1. Susceptibility of X17CrNi16-2 martensitic stainless steel to hydrogen embrittlement after conventional and deep cryogenic heat treatmentMirjam Bajt Leban, Bojan Zajec, Bojan Podgornik, Črtomir Donik, Patricia Jovičević Klug, Miha Hren, Andraž Legat, 2024, original scientific article Abstract: A low carbon/ high chromium martensitic stainless steel, X17CrNi16-2, was heat treated using two different hardening and tempering regimes (1050 ◦ C/480 ◦ C or 980 ◦C/600 ◦C) — promoting either a high strength or high toughness state, respectively and further combined with deep cryogenic treatment (DCT) at 196 ◦C for 24 h. Over recent years DCT has been recognized as a promising technique to improve the properties of steel, predominantly with respect to its tensile strength, toughness and wear resistance. The influence of DCT on the hydrogen embrittlement resistance of martensitic stainless steel has not yet, however, been reported.
A slow strain rate tensile test (SSRT) with simultaneous cathodic hydrogen charging was selected as the method to assess potential susceptibility to hydrogen embrittlement (HE). Relatively low-intensity hydrogen charging, utilizing a constant current density of 0.1 mA/cm2, in a non-corrosive, slightly alkaline buffer solution, led to a clear reduction in the ultimate tensile stress. This reduction, and therefore the HE susceptibility, was more pronounced in the steel with a higher strength (i.e. that subject to the 1050 ◦C/ 480 ◦C heat treatment condition). Furthermore, DCT did not appear to have any impact on the steel’s mechanical properties in the presence of hydrogen. Fractographic analysis showed clear evidence of HE in the hydrogen-charged specimens.
This paper presents results of the SSRT tests and further fractography results, and discusses the impact of conventional and deep cryogenic treatment on HE susceptibility.
Keywords: martensitic stainless steel, deep cryogenic treatment, hydrogen embrittlement, slow strain rate tensile test
Published in DiRROS: 23.05.2024; Views: 76; Downloads: 76
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2. The effect of heat treatment on the interface of 155 PH martensitic stainless steel and SAF 2507 duplex steel in functionally graded AM componentsMartina Koukolíková, Pavel Podaný, Sylwia Rzepa, Michal Brázda, Aleksandra Kocijan, 2023, original scientific article Abstract: Multi-material components, also known as functionally graded materials (FGMs), are innovative materials that possess unique properties due to their composition and have many potential applications in engineering and science. The effect of the heat treatment (HT) of functionally graded materials 15–5 precipitation-hardened (PH) martensitic steel and SAF 2507 duplex stainless steel (and the opposite order of deposition, i.e. SAF 2507 first followed by 15–5 PH stainless steel) on the interface microstructures was systematically investigated in the presented research. The choice of HT followed the trend of optimum post-processing for the individual alloys. A significant modification in the interface microstructure, characterized in the microstructural transition zone (MTZ) formed above the fusion line. Mechanical properties by miniaturized testing method including hardness measurement characterized both types of interfaces. The sequence of the materials’ application did not have a significant effect on their final mechanical tensile properties in the heat-treated states. Nevertheless, the microstructural change at the MTZ led to drop in the hardness at the interface. The research presents heat-treated FGMs in a horizontal configuration to form a high-quality metallurgical joint between heterogeneous materials manufactured by powder-based directed energy deposition method.
Keywords: heat treatment, additive manufacturing, martensitic stainless steel, duplex steel, microstructure, mechanical properties
Published in DiRROS: 04.04.2024; Views: 147; Downloads: 28
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3. Effect of post-treated low-temperature plasma nitriding on the wear and corrosion resistance of 316L stainless steel manufactured by laser powder-bed fusionMatjaž Godec, Črtomir Donik, Aleksandra Kocijan, Bojan Podgornik, Danijela Anica Skobir Balantič, 2020, original scientific article Keywords: austenitic stainless steel, powder bed fusion, low-temperature plasma nitriding, wear and corrosion behaviour, dislocation cell structure
Published in DiRROS: 25.03.2024; Views: 151; Downloads: 82
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4. A comparative analysis among quenched, tempered, and stepped cooled TIG welded SS-304 plates based on tensile strength, hardness, and microstructural appearanceSaurabh Dewangan, Saksham Saksham, Adhir Chandra Paul, Jaka Burja, 2023, original scientific article Keywords: welding, austenitic stainless steel, heat affected zone, mechanical properties
Published in DiRROS: 15.03.2024; Views: 141; Downloads: 66
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5. Ladle melt treatment of high sulfur stainless steelsJaka Burja, 2024, published scientific conference contribution Abstract: The influence of sulfur on both slag and melt is very important in steelmaking. This is especially true for highsulfur machining steels. Machinability is achieved by alloying high sulfur contents, above 300 ppm. These are steels that form small chips and shavings during mechanical processing by cutting, which is more appropriate and favorable for both the workpiece and the processing tool and machine. However, the secondary steelmaking slag is typically designed for desulfurization. This means that the sulfur content rapidly falls after sulfur additions. This is especially true for high machinability stainless steel grades where S contents can exceed 1000 ppm. This causes the sulfur wire yield to vary greatly in each charge, making the process unreliable. Some aspects of understanding the interaction between the steel melt and slag and the effect on casting are presented in this work. Based on industrial charges, we analyzed the yield of sulfur additions and the influencing factors on the efficiency of the sulfur addition. The lower slag basicity was linked to lover sulfur distribution rations, and lover sulfur distribution rations were linked to higher sulfur yields. Melt and slag samples were analyzed. Slag entrapment during ingot casting was linked to the high sulfur contents.
Keywords: desulfurization, sulfur, stainless steel, steelmaking
Published in DiRROS: 28.02.2024; Views: 203; Downloads: 72
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6. Austenite reversion suppression with deep cryogenic treatment : a novel pathway towards 3rd generation advanced high-strength steelsPatricia Jovičević Klug, Matic Klug Jovičević, Lars Thormählen, Jeffrey McCord, Michael Rohwerder, Matjaž Godec, Bojan Podgornik, 2023, original scientific article Keywords: Martensitic stainless steel, deep cryogenic treatment, microstructure, mechanical properties, microstructural transformations, phase transformation
Published in DiRROS: 02.02.2024; Views: 197; Downloads: 95
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7. Complex interdependency of microstructure, mechanical properties, fatigue resistance, and residual stress of austenitic stainless steels AISI 304LPatricia Jovičević Klug, Matic Klug Jovičević, Michael Rohwerder, Matjaž Godec, Bojan Podgornik, 2023, original scientific article Keywords: stainless steel, AISI 304L, deep cryogenic treatment (DCT), microstructure, mechanical properties, fatigue, residual stress
Published in DiRROS: 02.02.2024; Views: 231; Downloads: 99
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8. Tribological evaluation of vegetable ▫$oil/MoS_2$▫ nanotube-based lubrication of laser-textured stainless steelMarjetka Conradi, Bojan Podgornik, Maja Remškar, Damjan Klobčar, Aleksandra Kocijan, 2023, original scientific article Abstract: In the present work, the functionalisation of austenitic stainless steel, AISI 316L surfaces via nanosecond Nd:YAG laser texturing in order to modify the surface morphology with crosshatch and dimple patterns is presented. A tribological analysis under lubrication with sunflower and jojoba oil with and without the addition of a solid lubricant, MoS2 nanotubes, was performed. In conjunction with friction/wear response laser-textured surface wettability, oil spreadability and oil retention capacity were also analysed. It was shown that the crosshatch pattern generally exhibited lower friction than the dimple pattern, with the addition of MoS2 nanotubes not having any significant effect on the coefficient of friction under the investigated contact conditions. This was found in addition to the better oil spreadability and oil retention capacity results of the crosshatch-textured surface. Furthermore, texturing reduced the wear of the stainless-steel surfaces but led to an approximately one order of magnitude larger wear rate of the steel counter-body, primarily due to the presence of hard bulges around the textured patterns. Overall, the crosshatch pattern showed better oil retention capacity and lower friction in combination with different vegetable oils, thus making it a promising choice for improving tribological performance in various environmentally friendly applications.
Keywords: tribology, stainless steel, vegetable oil lubrication, MoS2 nanotubes
Published in DiRROS: 02.02.2024; Views: 165; Downloads: 87
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9. Aspects of bending high-borated austenitic stainless steel sheets for interim storage of spent nuclear fuelJosef Odehnal, Tomáš Studecký, Petra Čejková, Ivana Poláková, Martin Rund, Václav Bruná, Petr Martinek, Pavel Francisko, Črtomir Donik, 2023, original scientific article Keywords: interim storage, spent fuel, borated stainless steel, cold working, bending
Published in DiRROS: 01.02.2024; Views: 182; Downloads: 85
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10. Influence of boron and nitrogen on the machinability, polishability and wear of martensitic stainless steelsMarko Sedlaček, Barbara Šetina, Vesna Žepič Bogataj, Jaka Burja, 2023, original scientific article Keywords: martensitic stainless steel, boron, nitrogen, wear, machinability, polishability
Published in DiRROS: 01.02.2024; Views: 202; Downloads: 96
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