1. High temperature oxidation of EN AW 7075 aluminium alloyNejc Velikajne, Tilen Balaško, Jaka Burja, Matjaž Godec, Irena Paulin, 2024, published scientific conference contribution Abstract: 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. Keywords: EN AW 7075, high-temperature oxidation, oxide film, selective laser melting Published in DiRROS: 28.02.2024; Views: 392; Downloads: 179
Full text (897,18 KB) This document has many files! More... |
2. Solidification behavior of Fe-6.5Si alloy powder for AM-SLM processing, as assessed by differential scanning calorimetryDarja Steiner Petrovič, Črtomir Donik, Irena Paulin, Matjaž Godec, Maja Vončina, Martin Petrun, 2023, original scientific article Keywords: soft magnetic alloy, differential scanning calorimetry, oxygen, high-temperature phase, microstructure, eutectics Published in DiRROS: 02.02.2024; Views: 384; Downloads: 168
Full text (9,05 MB) This document has many files! More... |
3. High-temperature oxidation of boiler steels at 650 °CJaka Burja, Barbara Šetina, Borut Žužek, Tilen Balaško, 2023, original scientific article Abstract: This study presents a comprehensive investigation of the formation, composition and
behaviour of oxide layers during the high-temperature oxidation of four different steel alloys (16Mo3,
13Cr, T24 and P91) at a uniform temperature of 650 °C. The study is aimed at assessing the oxidation
damage due to short-term overheating. The research combines CALPHAD (CALculation of PHAse
Diagrams) calculations, thermogravimetric analysis (TGA) and advanced microscopy techniques, in-
cluding scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD), to elucidate
the complex mechanisms controlling oxidation kinetics and oxide layer development. CALPHAD
calculations were used to determine the thermodynamically stable phases for each steel type at 650
◦C and different oxygen activities. The results showed different phase compositions, highlighting
the importance of the chromium content in steel for the formation of oxide layers. The different
oxidation kinetics and oxide layer compositions are presented and associated with the increased risk
of material degradation due to overheating. These results have significant implications for industrial
applications, mainly the susceptibility to oxidation of low-alloyed steels like 16Mo3 and 13 Cr and
contribute to a deeper understanding of oxidation processes in steels. Keywords: high-temperature oxidation, thermogravimetric analysis, kinetics, CALPHAD, boiler steels, SEM, EBSD Published in DiRROS: 26.01.2024; Views: 445; Downloads: 203
Full text (12,99 MB) This document has many files! More... |
4. High temperature friction and galling properties of nanolayered (Cr,V)N coatings and effect of V contentBojan Podgornik, Marko Sedlaček, Barbara Šetina, Miha Čekada, 2023, original scientific article Keywords: (Cr, V)N coating, galling, high-temperature tribology, hot forming, self-lubrication Published in DiRROS: 26.01.2024; Views: 398; Downloads: 219
Full text (12,53 MB) This document has many files! More... |
5. High temperature resistant fly-ash and metakaolin-based alkali-activated foamsKatja Traven, Mark Češnovar, Srečo D. Škapin, Vilma Ducman, 2021, original scientific article Abstract: Alkali-activated foams (AAFs) present one of the most promising materials for use in the construction sector. Their main advantages lie in their utilization of waste material and their ability to form at temperatures well below 100 °C, while still competing in performance with foamed glass or ceramics. The present body of research has focused on improving the thermal stability of fly-ash foams by i) adding metakaolin, and ii) changing the activator from sodium-based to potassium-based components. It has been confirmed that a certain increase in thermal resistance is achieved through the addition of metakaolin while changing activators played a crucial role. While sodium-based AAFs without metakaolin start to shrink at approximately 600 °C, samples that have had metakaolin added start to shrink at approximately 700 °C. Samples without metakaolin that have used a potassium activator start to shrink at approximately 800 °C, whereas potassium-based samples with the addition of metakaolin start to shrink at approximately 900 °C. Keywords: alkali activated materials, geopolymers, high temperature, resistance, foams Published in DiRROS: 01.08.2023; Views: 517; Downloads: 323
Full text (13,91 MB) This document has many files! More... |
6. Comparison of cycling high temperature corrosion at 650°C in the presence of NaCl of various austenitic stainless steelsMirjam Bajt Leban, Maja Vončina, Tadeja Kosec, Robert Tisu, Matevž Barborič, Jože Medved, 2023, original scientific article Abstract: The high temperature corrosion at 650°C in the presence of NaCl at atmospheric pressure of AISI 304L, AISI 309, AISI 310S, AISI 314 and AISI 321 austenitic stainless steel was studied. The specimens were cyclically heated in the furnace and immersed in a 3.5% aqueous NaCl solution after cooling for 15 min. After each cycle, the change in mass of the samples was measured. The corroded samples were analysed by SEM /EDX, and the corrosion products were analysed by XRD. The chloride ions react with the steel surface to form porous and poorly adherent oxides and metal chlorides. After the mass increase during the first exposure cycles, spalling of the oxides occurred. The high temperature austenitic stainless steels (AISI 309, AISI 310S, AISI 314) showed less mass loss than conventional austenitic steels (AISI 304L). Surprisingly, the stainless steel AISI 321 showed a similar low weight loss after the cyclic test as AISI 309, but a detailed analysis of the exposed surfaces after the test showed a similar corrosion attack as for AISI 304. After the cyclic test at high temperature in the presence of NaCl, a higher concentration of Cr and Ni definitely improves the corrosion resistance under the present conditions, but a certain addition of Si is even more obvious. Keywords: austenitic stainless steel, high temperature corrosion, NaCl, exhaust systems, open access Published in DiRROS: 31.05.2023; Views: 460; Downloads: 290
Full text (1,53 MB) This document has many files! More... |
7. |