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Contemporary Methods of Protection and Restoration of Components
Published in E. S. Gevorkyan, M. Rucki, V. P. Nerubatskyi, W. Żurowski, Z. Siemiątkowski, D. Morozow, A. G. Kharatyan, Remanufacturing and Advanced Machining Processes for New Materials and Components, 2022
E. S. Gevorkyan, M. Rucki, V. P. Nerubatskyi, W. Żurowski, Z. Siemiątkowski, D. Morozow, A. G. Kharatyan
Among non-oxide materials for high-temperature applications, molybdenum disilicide (MoSi2) is widely used to protect Mo-based alloys from oxidation due to its excellent oxidation resistance at high temperatures and low preparation cost (Zhang et al., 2018). MoSi2 is a high-melting-point intermetallic compound noted for its excellent resistance to oxidation and thermal expansion coefficient closer to that of metallic substrates comparing to other oxides. Therefore, oxide spallation from the substrate caused by a large mismatch of thermal expansion coefficient in thermal cycles can be avoided. It is thought that by further oxygen diffusion into the substrate following MoSi2 formation, a thin layer of SiO2 is formed over the MoSi2 layer, which protects the underlying metal from further inward oxygen diffusion and oxidation (Seo et al., 2012).
Coexistence of two different atomic structures in the Σ13 pyramidal twin boundary in α-Al2O3
Published in Philosophical Magazine Letters, 2019
Saki Ishihara, Eita Tochigi, Ryo Ishikawa, Naoya Shibata, Yuichi Ikuhara
To fabricate a bicrystal under a controlled gas atmosphere, we developed a crystal bonding furnace with a gas flow system. A schematic view of the furnace is shown in Figure 1. The main chamber of the furnace is made of an alumina tube which has a gas inlet and outlet to keep the gas flow during heating. The heaters are molybdenum disilicide rods (Kanthal Super, Sandvik AB, Sweden) and the maximum temperature reached was approximately 1500°C at the sample position. Two opposed alumina rods are located in the chamber. The upper rod is connected to a loading device with feedback control and can apply a constant force to a sample.
Mechanical Properties and Unlubricated Sliding Wear Behavior Study of Silicon Nitride-Based Cermets
Published in Tribology Transactions, 2022
Sushree Sefali Mishra, Debasis Chaira
In the work reported here, Si3N4 cermets reinforced with molybdenum (Mo) and silicon (Si) and oxide additives (Y2O3 and Al2O3) have been fabricated, and nonlubricated dry sliding behavior has been studied. The purpose of choosing Mo and Si is the minimal differences in the coefficient of thermal expansion (CTE) between matrix and reinforcement phases. There may be comparatively lesser grain pull-out than for monolithic Si3N4 by limiting the thermal expansion mismatch (19). The effects of oxide sintering additives, such as, Al2O3 and Y2O3, and Si reinforcement on wear behavior have also been discussed. The rationale behind focusing on the Si3N4-reinforced Mo is to form the molybdenum disilicide phase (MoSi2), which is hard and of self-lubricating nature. Y2O3 and Al2O3 have been added as sintering additives to enhance the sinterability, and their contents are varied to find the levels of additives required for optimal mechanical and tribological properties. The novelty of this recent study is that it focuses on the tribological phenomena of the cermets. In this study we have focused only on the surface phenomena, wear mechanism, and wear outcomes with the variation in normal load. The worn cermet surfaces have been analyzed under a scanning electron microscope (SEM) coupled with energy-dispersive x-ray spectroscopy (EDS). The effects of various wear parameters like load, speed, and sliding time on the wear behavior, wear rate, and coefficient of friction (COF) have been investigated. The microstructural changes during wear have been investigated in detail and proposed wear mechanisms have been discussed elaborately.
Distribution of vanadium between Al2O3-CaO-MgO-SiO2-TiO2 slag and carbon saturated iron
Published in Mineral Processing and Extractive Metallurgy, 2021
Equilibration experiments were performed in a vertical tube furnace with an alumina work tube (50 mm ID) with brass end caps that permitted atmosphere control. A molybdenum disilicide heating element furnace was used to provide external heat to the work tube. With the work tube in place, the furnace provided a region of constant temperature (within ± 2°C) about 50 mm long, located close to the middle of the furnace.