1. Microstructure and mechanical performance of AISI D2 tool steel after standard and modified deep cryogenic treatmentVenu Yarasu, Bojan Podgornik, Barbara Šetina, Marko Sedlaček, Črtomir Donik, Francisco Ruiz-Zepeda, 2025, izvirni znanstveni članek Ključne besede: steel, isothermal heat treatments, cyclic response, martensite, fracture toughness
Objavljeno v DiRROS: 23.05.2025; Ogledov: 226; Prenosov: 96
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4. Laser surface modification of CRVN coatings for self-lubricating performanceBojan Podgornik, Barbara Šetina, Miha Čekada, Suman Chatterjee, Dermot Brabazon, 2025, objavljeni znanstveni prispevek na konferenci Ključne besede: CrVN coating, laser modification, hot forming, self-lubrication, wear, friction
Objavljeno v DiRROS: 14.05.2025; Ogledov: 194; Prenosov: 53
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5. Combining ultrafast laser texturing and laser hardening to enhance surface durability by improving hardness and wear performanceAbhijit Cholkar, Suman Chatterjee, Sujith Kumar, Marko Sedlaček, Bojan Podgornik, David Kinahan, Dermot Brabazon, 2024, izvirni znanstveni članek Povzetek: Aluminum alloy 7075 is utilized widely across marine, aerospace, and automotive sectors. However, its surface wear resistance has hindered its application in certain tribological environments. Addressing this challenge, the current study examines a hybrid laser method to increase surface wear resistance by combining two techniques: ultrafast laser texturing and laser-based surface hardening. Ultrafast laser processing is conducted using 3 W laser power, 100 kHz pulse repetition rate, 4 mm s-1 scanning speed, and three different scan patterns. After the texturing operation, laser-based surface hardening is then performed on these textures using a continuous wave laser. The laser heat treatment is conducted using laser powers of 400 and 500 W with three different scan speeds of 1, 2, and 3 mm s-1 . Microhardness evaluations show a notable increase in hardness, with the hardest sample exhibiting a 17.8% increase compared to the pristine sample. The lasertextured and laser heat-treated samples exhibit a significant reduction in the average coefficient of friction and wear volumes compared to samples that were laser-textured but not laser heat-treated. The investigated laser processing strategy offers a promising approach for surface modification, enhancing both mechanical properties and wear resistance of aluminum alloy 7075 surfaces.
Ključne besede: hardness, laser hardening, parametric modeling, surface modification, ultrafast laser texturing, wear resistance
Objavljeno v DiRROS: 05.11.2024; Ogledov: 379; Prenosov: 849
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6. Enhancing magnesium bioactivity for biomedical applications : effects of laser texturing and sandblasting on surface propertiesMarjetka Conradi, Aleksandra Kocijan, Bojan Podgornik, 2024, izvirni znanstveni članek Povzetek: Magnesium and its alloys, valued for their lightweight and durable characteristics, have garnered increasing attention for biomedical applications due to their exceptional biocompatibility and biodegradability. This work introduces a comparison of advanced and basic methods—laser texturing and sandblasting—on magnesium surfaces to enhance bioactivity for biomedical applications. Employing a comprehensive analysis spanning surface morphology, hardness, wettability, tribological performance, and corrosion behavior, this study elucidates the intricate relationship between varied surface treatments and magnesium’s performance. Findings reveal that both laser texturing and sandblasting induce grain refinement. Notably, sandblasting, particularly with a duration of 2 s, demonstrates superior wear resistance and reduced corrosion rates compared to untreated magnesium, thereby emerging as a promising approach for enhancing magnesium bioactivity in biomedical contexts. This investigation contributes to a deeper understanding of the nuanced interactions between diverse surface treatments and their implications for magnesium implants in chloride-rich environments, offering valuable insights for prospective biomedical applications.
Ključne besede: biomaterial, microstructure, hardness, friction/wear, corrosion
Objavljeno v DiRROS: 18.10.2024; Ogledov: 401; Prenosov: 12554
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7. Effect of Ti and S content on the properties and machinability of low-carbon ferritic–pearlitic steelBoštjan Arh, Franc Tehovnik, Franci Vode, Bojan Podgornik, 2024, izvirni znanstveni članek Povzetek: This research was focused on the effect of Ti and S content on the formation of non-metallic inclusions and their influence on the mechanical properties and machinability of low-carbon ferritic– pearlitic steels. An analysis and classification of the non-metallic inclusions were carried out. The tensile strength and impact toughness were determined from samples taken in the rolling direction. Machinability investigations were carried out on a CNC turning machine and by analyzing the surface roughness. TiO-TiN inclusions are present in steels with an increased Ti content. In these steels, the hardness, tensile strength, and cutting forces increase with a higher proportion of Ti. In the second group of steels with increased contents of S, Al, and Ca, MnS and CaO-Al2O3-MnS non-metallic inclusions are formed. As the S content increases, the tensile strength and cutting forces decrease, while the impact toughness increases. In steels with added Ti, the This research was focused on the effect of Ti and S content on the formation of non-metallic inclusions and their influence on the mechanical properties and machinability of low-carbon ferritic– pearlitic steels. An analysis and classification of the non-metallic inclusions were carried out. The tensile strength and impact toughness were determined from samples taken in the rolling direction. Machinability investigations were carried out on a CNC turning machine and by analyzing the surface roughness. TiO-TiN inclusions are present in steels with an increased Ti content. In these steels, the hardness, tensile strength, and cutting forces increase with a higher proportion of Ti. In the second group of steels with increased contents of S, Al, and Ca, MnS and CaO-Al2O3-MnS non-metallic inclusions are formed. As the S content increases, the tensile strength and cutting forces decrease, while the impact toughness increases. In steels with added Ti, the machining is more difficult, but a finer surface is achieved after turning, while a higher S content results in an increased fraction of softer sulfide inclusions, which reduce the cutting forces but also result in a reduced surface quality. turning, while a higher S content results in an increased fraction of softer sulfide inclusions, which reduce the cutting forces but also result in a reduced surface quality.
Ključne besede: non-metallic inclusions, mechanical properties, machinability, surface roughness
Objavljeno v DiRROS: 03.09.2024; Ogledov: 563; Prenosov: 599
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8. 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, izvirni znanstveni članek Povzetek: 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.
Ključne besede: martensitic stainless steel, deep cryogenic treatment, hydrogen embrittlement, slow strain rate tensile test
Objavljeno v DiRROS: 23.05.2024; Ogledov: 764; Prenosov: 566
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9. Sliding wear behaviour of conventional and cryotreated PM Cr-V (Vanadis 6) ledeburitic tool steelVenu Yarasu, Peter Jurči, Peter Gogola, Bojan Podgornik, Marko Sedlaček, 2023, izvirni znanstveni članek Ključne besede: cold work tool steel, conventional treatment, cryogenic treatment, hardness, reciprocal sliding, wear
Objavljeno v DiRROS: 08.04.2024; Ogledov: 952; Prenosov: 163
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10. 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, izvirni znanstveni članek Ključne besede: austenitic stainless steel, powder bed fusion, low-temperature plasma nitriding, wear and corrosion behaviour, dislocation cell structure
Objavljeno v DiRROS: 25.03.2024; Ogledov: 736; Prenosov: 441
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