We provide data obtained by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) on the interaction of ingested tungsten nanofibers with epithelial cells of the digestive tubes of a test organism Porcellio scaber. No toxicity was detected in any of exposed animals after 14 days of feeding on tungsten nanofiber dosed food, but when nanofibers enter the digestive system they can react with epithelial cells of the digestive tubes, becoming physically inserted into the cells. In this way, nanofibers can injure the epithelial cells of digestive gland tubes when they are ingested with food. Our SEM data suggest that peristaltic forces may have an important role, not predicted by in vitro experiments, in the interactions of nanomaterials with digestive intestinal cells.
COBISS.SI-ID: 7564409
Fracture toughness is one of the main material properties used when selecting and optimizing heat treatment of tools. However, fracture toughness data alone is not sufficient and need to be supported by other material properties and features. The aim of the present research work was to correlate fracture toughness properties of hot-work tool steel, especially its variation to the local microstructure, microhardness, and composition and to establish methodology for proper evaluation of tool steel's fracture toughness. Results show that the pressure of any weak point, either in a form of non-metallic inclusions and/or large undissolved eutectic carbide clusters, located in the region of positive segregation with high microhardness will lead to considerable reduction in fracture toughness.
COBISS.SI-ID: 1001898
The limited load-carrying capacity of tool steels greatly restricts the use of hard coatings in forming applications. This can, however, be improved by increasing the substrate's hardness, but especially for hot forging, the fracture toughness and resistance to cracking are equally important. The present work was focused on the possibilities of combining a vacuum heat treatment, a deep-cryogenic treatment and plasma nitriding in order to improve the properties of PACVD-coated tool steel. The results show that for the most demanding forming operations the substrate toughness is far more important than the hardness, especially at elevated temperatures, with just a vacuum-heat-treated steel substrate giving the best support for the top coating.
COBISS.SI-ID: 995754
Differential scanning calorimetry, thermodynamic calculations, and metallographic analyses were used for a determination of the solidification sequence in a Fe–2.42 %Si–0.5 %Al–0.94 %Mn alloy. According to the thermodynamic calculations the two-phase region in the selected Fe–Si–Al–Mn alloy is stable between 1303 and 913 °C. The highest mass-fraction of the γ-phase is reached at 1150 °C. With decreasing temperature the austenite retransforms into ferrite. In the temperature range where the thermodynamic calculations predict the existence of the two-phase region in the DSC curves, weak thermal events were observed. A post-exposure metallographic analysis revealed that the substructures in the ferrite microstructure indicate the γ → α phase transformation.
COBISS.SI-ID: 1376863
Currently the best overall appraisal of tool and high-speed steel applicability seems to be a combination of fracture toughness, bending, or compression testing and in specific cases of impact or small-punch creep test. This paper clearly demonstates usability of a single KIc-test specimen for determination of a wide range of properties being important for tool and high-speed steels, and their vacuum-heat-treatment optimization. In the case of ESR AISI M2 high-speed steel low tempering and austenitizing temperature are preferable in terms of ductility and toughness, high tempering and lower austenitizing temperatures in terms of bending strength and high-speed machinability, while high austenitizing and mid tempering temperatures in terms of hardness, compression strength and grindability.
COBISS.SI-ID: 1001642