1. Processing aluminium EN AW 7075 alloy using selective laser meltingNejc Velikajne, Jože Medved, Matjaž Godec, Irena Paulin, zaključena znanstvena zbirka raziskovalnih podatkov Povzetek: Selective laser melting (SLM) is an additive manufacturing process, forming the desired geometry by selective layer fusion of powder material. Unlike conventional manufacturing processes, highly complex parts can be designed and manufactured with high accuracy and little post processing. Currently, different types of steel, aluminium, titanium and nickel-based alloys have been successfully processed; however, high strength aluminium alloy EN AW 7075 has not been processed with satisfying quality. The main focus of the investigation is to develop a new alloy which is more suitable for the SLM process for the wide used aluminium alloy EN AW 7075. But before that, gas-atomized powder material was characterized in terms of statistical distribution. A wide range of process parameters and different pre-heating temperatures were selected to optimize the process in terms of optimum volume density and reducing the effect of hot cracking. However, all laser-melted parts exhibited hot cracks which typically appear in aluminium alloy EN AW 7075.
Ključne besede: EN AW 7075, aluminium alloy, hot cracks, relative density, selective laser melting (SLM)
Objavljeno v DiRROS: 22.04.2024; Ogledov: 71; Prenosov: 0 |
2. A coupled convective-diffusive model of heat transfer and melt-pool dynamics in additive manufacturingTijan Mede, Matjaž Godec, 2024, elaborat, predštudija, študija Ključne besede: additive manufacturing, selective laser melting, laser powder-bed fusion, melt-pool, heat transfer, convection
Objavljeno v DiRROS: 05.04.2024; Ogledov: 85; Prenosov: 0 |
3. Use of plasma nitriding to improve the wear and corrosion resistance of 18Ni-300 maraging steel manufactured by selective laser meltingMatjaž Godec, Bojan Podgornik, Aleksandra Kocijan, Črtomir Donik, Danijela Anica Skobir Balantič, 2021, izvirni znanstveni članek Ključne besede: selective laser melting, 18Ni-300 maraging steel, heat treatment, plasma nitriding, retained and reverted austenite, wear and corrosion behaviour
Objavljeno v DiRROS: 25.03.2024; Ogledov: 114; Prenosov: 60
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4. High temperature oxidation of EN AW 7075 aluminium alloyNejc Velikajne, Tilen Balaško, Jaka Burja, Matjaž Godec, Irena Paulin, 2024, objavljeni znanstveni prispevek na konferenci Povzetek: Aluminium alloys are highly valued for their exceptional strength-to-weight ratio, making them a preferred choice in structural applications. Among these alloys, EN AW 7075 stands out for its superior mechanical properties, finding widespread use in industries such as aerospace, mechanical engineering, and sports equipment. This study investigates the high-temperature oxidation behavior of EN AW 7075 alloy. The gathered results can provide valuable insights into the behavior of the mentioned alloy during the selective laser melting (SLM) process. These results can contribute to a better understanding of how the alloy responds to specific conditions and parameters. SLM is an additive manufacturing technique. The process involves the sequential steps of preheating, melting, and rapid cooling of metal powder. To minimize the influence of oxygen, the build chamber is filled with inert gas. A protective argon atmosphere is continuously maintained. However, despite these precautions, oxidation can still occur, leading to potential issues in the final product. Hence, we examined the oxidation kinetics of the EN AW 7075 alloy in an oxygen atmosphere in the temperature range of 300-500 °C. The findings of this investigation significantly contribute to an understanding of the behavior of the alloy during high-temperature oxidation, particularly for ongoing studies focused on processing Al-Zn-Mg-Cu alloys using the selective laser melting technique. Thermogravimetry was employed to analyze the oxidizing behavior, with three samples subjected to a 6-hour exposure in an oxidizing atmosphere at temperatures of 300, 400, and 500 °C. Surprisingly, no oxidation occurred, as indicated by the negligible and negative changes in mass observed across all samples.
Ključne besede: EN AW 7075, high-temperature oxidation, oxide film, selective laser melting
Objavljeno v DiRROS: 28.02.2024; Ogledov: 170; Prenosov: 70
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5. The microstructure, mechanical and electrochemical properties of 3D printed alloys with reusing powdersMirjam Bajt Leban, Miha Hren, Tadeja Kosec, 2023, izvirni znanstveni članek Povzetek: CoCrMo and Ti6Al4V are widely used in medical, dental and 3D printing technology, allowing the accurate fabrication of geometrically complicated structures. In order to reduce the costs of printed objects, the reuse of powder is common daily practice. AQ1 When using 3D printing technology, the direct impact of elevated temperatures and the influence of the laser beam may change the properties of the powder when it is reused, thus affecting the final properties of the printed object. The main aim of the present study was to investigate the impact of reused powder on the mechanical, microstructural and electrochemical properties of 3D printed objects. 3D printed objects fabricated from virgin and reused powder of both alloys were analyzed by metallographic observation, computed tomography, XRD and electrochemical methods. The main finding of the study was that the use of reused powder (recycled 3 times) does not detrimentally affect the mechanical and corrosion integrity of 3D printed CoCr and Ti6Al4V alloys, especially for the purpose of applications in dentistry.
Ključne besede: additive manufacturing, selective laser melting, virgin powder, reused powder, microtomography
Objavljeno v DiRROS: 08.01.2024; Ogledov: 213; Prenosov: 101
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6. Estimation of the corrosion properties for titanium dental alloys produced by SLMTadeja Kosec, Mirjam Bajt Leban, Maja Ovsenik, Matej Kurnik, Igor Kopač, 2022, izvirni znanstveni članek Povzetek: Titanium alloys are known for their excellent biocompatible properties. The development of additive-manufacturing technologies has increased the interest in the use of Ti-6Al-4V, produced by selective laser melting (SLM) method, also in dentistry, i.e., prosthodontics and orthodontics. In the present paper, the effect of laser printing parameters in the selective laser melting (SLM) process on the porosity and corrosion behavior of Ti-6Al-4V dental alloy was metallographically and electrochemically studied. All the tests were performed in artificial saliva at 37 °C. Different forms of Ti-6Al-4V alloy were selected: a reference sample, i.e., pre-fabricated milling disc in wrought condition and four different 3D-printed samples made from Ti-6Al-4V powder using the SLM method, one being heat treated. Electrochemical, spectroscopic and hardness measurements were employed in the study. It was shown that the SLM-produced Ti-6Al-4V samples with different printing parameters have similar microstructural and electrochemical properties, while the electrochemical properties of a reference and thermally treated 3D-printed sample were different, most probably due to the change in the microstructure of the alloys. The corrosion properties were related to the microstructural properties as well as to the pore density.
Ključne besede: Ti-6Al-4V, dental alloys, artificial saliva, selective laser melting, corrosion
Objavljeno v DiRROS: 31.05.2023; Ogledov: 258; Prenosov: 115
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7. Differences between 3-D printed and traditionally milled CoCr dental alloy from casted block in oral environmentMirjam Bajt Leban, Matej Kurnik, Igor Kopač, Matic Klug Jovičević, Bojan Podgornik, Tadeja Kosec, 2023, izvirni znanstveni članek Povzetek: The aim of this study was to compare corrosion resistance and ion release in CoCr dental alloys with identical chemical compositions produced using different technologies (SLM – selective laser melting and milling from cast blocks) and heat treatment (SLM parts only). The corrosion properties were tested in artificial saliva, artificial saliva with fluoride ions, and artificial saliva with added lactic acid to simulate inflammations. The study included electrochemical tests, microstructural investigation and ion release tests in the three different environments for a total of 42 days. The best performance of CoCr as a result of potentiodynamic polarization was observed in the artificial saliva with added lactic acid, which is in contradiction with the highest ion release measured from all the materials tested and electrochemical impedance spectroscopy that showed a deterioration of the passive layer in an acidic environment. Microstructural investigation revealed that different phases precipitated by heat treatment trigger increased release of Mo and W ions. The printing method does not raise critically ion release from CoCr alloy, while the state of the surface greatly impacts the extent of the ion release. This study demonstrates the importance of an interdisciplinary approach to the study of corrosion and biocompatibility in dental alloys.
Ključne besede: CoCr dental alloy, selective laser melting, corrosion, ion release, artificial saliva
Objavljeno v DiRROS: 29.05.2023; Ogledov: 343; Prenosov: 290
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