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Query: "author" (Bojan Podgornik) .

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1.
Effect of deep cryogenic treatment on aging behavior and properties of Al-Mg-Si alloy
Bojan Podgornik, Matic Klug Jovičević, Patricia Jovičević Klug, 2023, published scientific conference contribution

Keywords: deep cryogenic treatment, Al-Mg-Si alloy, aging, microstructure, hardness, fatigue
Published in DiRROS: 08.07.2025; Views: 24; Downloads: 4
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2.
Influence of laser beam shape and post heat-treatment on the microstructure and mechanical properties of nickel-based alloy IN718 manufactured by laser powder bed fusion
Matjaž Godec, Narges Mirzabeigi, Črtomir Donik, Danijela Anica Skobir Balantič, Simon Malej, Irena Paulin, Bojan Podgornik, Jonas Grünewald, Tobias Novotny, Florian Bayer, Francisco Ruiz-Zepeda, Katrin Wudy, 2025, original scientific article

Abstract: This study examines the effect of Gaussian and ring-shaped laser beam profiles on the microstructural development and mechanical properties of the PBF-LB/M processed nickel-based alloy Inconel 718 in its as-built and post-heat-treated conditions. Beam shaping was employed to achieve a faster build rate without compromising material properties. One of the objectives was to optimise heat treatment conditions for the beam-shaped profile. The post-heat-treatment process included four different solution annealing temperatures (954 °C, 984 °C, 1034 °C and 1154 °C), followed by two-step ageing, respectively. The microstructure evolution was revealed using scanning electron microscopy (SEM) equipped with energy-dispersive X-ray diffraction (EDS). The mechanical properties in all investigated conditions were evaluated based on tensile tests at room temperature. Using a Gaussian laser beam profile results in a fine-grained microstructure without a strong columnar orientation, while the ring beam profile produces a distinct columnar structure with larger nanodendritic grains and dislocation cells. Both beam profiles exhibit a similar proportion of Laves phase. After post-heat treatment, the Gaussian beam profile generally provides 3-7 % higher mechanical properties. The differences in mechanical properties between horizontal and vertical building directions are greater for ring-shaped laser beam profiles. Heat-treatment temperature above 1034 °C leads to recrystallisation, grain growth and the formation of carbonitrides which reduce mechanical properties. Based on the results, the proposed optimal heat-treatment temperature for both investigated laser beam shapes is 984 °C. At this temperature, tensile strength equalises between horizontal and vertical build directions while yield strength increases, which is beneficial for most applications.
Keywords: PBF-LB/M, beam shaping, IN718, heat treatment, mechanical properties
Published in DiRROS: 07.07.2025; Views: 43; Downloads: 11
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4.
The role of materials in the green transition: opportunities, challenges, barriers and consequences
Bojan Podgornik, 2025, original scientific article

Keywords: green transition, materials, renewable energy, recycling, sustainability
Published in DiRROS: 17.06.2025; Views: 121; Downloads: 71
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An optimized machine-learning tool to predict heat treatment response of hot-work tool steels
Venu Yarasu, Bojan Podgornik, 2025, original scientific article

Keywords: hot-work tool steel, machine learning, hardness, fracture toughness, graphical user interface
Published in DiRROS: 22.05.2025; Views: 269; Downloads: 108
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7.
Laser surface modification of CRVN coatings for self-lubricating performance
Bojan Podgornik, Barbara Šetina, Miha Čekada, Suman Chatterjee, Dermot Brabazon, 2025, published scientific conference contribution

Keywords: CrVN coating, laser modification, hot forming, self-lubrication, wear, friction
Published in DiRROS: 14.05.2025; Views: 241; Downloads: 71
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8.
Combining ultrafast laser texturing and laser hardening to enhance surface durability by improving hardness and wear performance
Abhijit Cholkar, Suman Chatterjee, Sujith Kumar, Marko Sedlaček, Bojan Podgornik, David Kinahan, Dermot Brabazon, 2024, original scientific article

Abstract: 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.
Keywords: hardness, laser hardening, parametric modeling, surface modification, ultrafast laser texturing, wear resistance
Published in DiRROS: 05.11.2024; Views: 440; Downloads: 869
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9.
Enhancing magnesium bioactivity for biomedical applications : effects of laser texturing and sandblasting on surface properties
Marjetka Conradi, Aleksandra Kocijan, Bojan Podgornik, 2024, original scientific article

Abstract: 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.
Keywords: biomaterial, microstructure, hardness, friction/wear, corrosion
Published in DiRROS: 18.10.2024; Views: 434; Downloads: 12581
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10.
Effect of Ti and S content on the properties and machinability of low-carbon ferritic–pearlitic steel
Boštjan Arh, Franc Tehovnik, Franci Vode, Bojan Podgornik, 2024, original scientific article

Abstract: 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.
Keywords: non-metallic inclusions, mechanical properties, machinability, surface roughness
Published in DiRROS: 03.09.2024; Views: 599; Downloads: 622
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