Vanadis®8 is a high-value tool steel, that undergoes gas atomization and hot isostatic pressing during production , resulting in costly waste. Repurposing this waste material through powder metallurgy (PM) offers a cost-effective solution. This study explores the PM process applied to Vanadis®8 steel scraps, involving high energy ball milling, uniaxial pressing, and sintering. The final product and the as-received steel underwent heat treatments, including quenching and tempering. Microstructural evaluation employed X-ray diffraction and scanning electron microscopy, while physical evaluation entailed Archimedes density measurements. Mechanical analysis was carried out through microhardness and compression strength tests. Results revealed that optimal milling conditions were achieved at 30 hours with 400 rpm (s-1). Vanadis®8 steel produced through PM attained 85% densification compared to the as-received material (6.31 g/cm3). MC-type carbides were present in all evaluated conditions. Heat treatments improved mechanical values for all conditions, suggesting that PM-produced Vanadis®8 steel, subjected to quenching and tempering, presents a viable reuse option.

Abstract The purpose of circular economy is to maximize resources efficiency. With the increase in consumption of raw materials, energy and waste generation, recycling is necessary for environmental and industrial reasons. Thus, the powder metallurgy, together with mechanical milling, stands as a new method for scraps recycling. This study aimed to produce UNS S31803 duplex stainless steel powders, with vanadium carbide (VC) addition as reinforcement, through mechanical milling. Different uniaxial compaction pressures (700, 800 and 900 MPa) were used, as well as sintering temperatures (1200, 1240 and 1280 °C) and times (1, 1.5 and 2 hours), in order to determine the best conditions. Particle size analysis, scanning electron microscopy and x-ray diffraction were used to characterize the powders. It was observed that the use of VC increased the comminution during the milling process, being obtained an average particle size of 42 μm. The highest density obtained was of 82% and hardness of 72%, in comparison with the steel from the manufacturing process. According to the analysis, it was verified that this method is viable, becoming an alternative route to reuse UNS S31803 duplex stainless steel scraps.

Abstract In this paper, Fe-15at.%Nb alloys were produced from high purity Fe (min. 99.8%) and Nb (min. 99.8%) powders via a mechanical alloying process. The effects of different Process Control Agents (i.e., methanol, hexane, and stearic acid) were investigated with powder morphologies, particle size distribution, and phase formation, and were sampled after up to 80 milling hours at 350 rpm. The powder morphologies and particle sizes were evaluated using scanning electron microscopy and laser diffraction analysis, respectively, and phases were identified via X-ray powder diffractometry. The results demonstrate for all conditions that, in the early stages, there was significant particle agglomeration due to the ductile-ductile feature of Fe and Nb powders, and latter an amorphization trend up to 80 milling hours. Methanol was the most efficient Process Control Agent in terms of avoiding cold welding, reducing of agglomeration, particle size distribution, reducing contamination and crystallinity reduction rate.

Abstract The Vanadis® 8 is a tool steel used in the manufacture of dies, punches and tools. It has a high carbon content combined with chromium, molybdenum and vanadium, and presents good performance in its mechanical properties. Usually, its chips obtained by machining are sold to companies that use remelting. However, this technique is considered expensive and harmful to the environment. Therefore, this work aimed to analyze the efficiency of the addition of vanadium carbide (VC) and molybdenum carbide (Mo2C) in the high energy ball milling of the Vanadis® 8 steel. Microstructural analysis were performed in the pure steel and with 3% of VC and Mo2C additions. The milling parameters used were: speed of 350 rpm, ball-to-powder weight ratio of 15:1 and times of 4, 8 and 12 hours. The results indicated that the Vanadis® 8 steel milled with VC presented the best microstructural results in all of the conducted tests.

Resumo Este estudo objetivou avaliar o conhecimento e as atitudes de estudantes de Educação Física de Universidades públicas do Estado do Rio de Janeiro, Brasil, em relação ao traumatismo dentário e uso de protetor bucal. Foram entrevistados 373 graduandos de três universidades públicas do Rio de Janeiro, através de questionário semiestruturado e padronizado. Os dados foram tabulados e analisados (SPSS 16.0), sendo obtida a frequência (%) e a relação dos mesmos (Teste qui-quadrado, p < 0,05). Apenas 3,21% dos entrevistados haviam recebido informação sobre traumatismo dentário e utilização do protetor bucal durante a graduação. Com relação à atitude dos graduandos, responderam corretamente apenas 19,83% a conduta frente a uma avulsão; 54,69% ao manuseio do dente avulsionado e 7,77% ao transporte do dente avulsionado. Ao se comparar essas atitudes em razão do período de graduação (< 5º período ou ≥ 5º período), informações prévias de trauma e experiências prévias de trauma, não se observou diferença significativa (p > 0,05). Tratando de prevenção, 89,81% conheciam o protetor bucal, embora apenas 17,96% o utilizavam durante atividades esportivas. Conclui-se que os alunos não recebem tais informações durante a graduação, mesmo possuindo em sua grade curricular a disciplina de primeiros socorros. Cabe aos cirurgiões dentistas desenvolver ações para que este conhecimento supra as necessidades dos futuros profissionais de educação física.

Abstract To evaluate the knowledge and attitudes in a group of Brazilian physical education undergraduate students, relative to dental trauma and use of mouthguard. A total of 373 undergraduates from three public universities of Rio de Janeiro were interviewed by means of a semi-structured standardised questionnaire. The data were tabulated and analyzed using the statistical program SPSS, 17.0. Frequency was performed and it was also applied the qui-quadrado (p < 0.05) test, to establish a relation between variables of interest. Only 3.21% of the interviewees had been given information on dental trauma and use of mouth protector during their undergraduate course. With regard to their attitudes, only 19.83% responded correctly about how to act towards a tooth avulsion; 54.69% about how to manage the avulsed tooth, and 7.77% about how to transport the avulsed tooth. By comparing these attitudes in relation to the undergraduate period (before or after the 5th semester), previous information and experience on dental trauma, it was observed no significant difference (p > 0.05). With regard to prevention, 89.81% knew mouthguard although only 17.96% wore it during sport activities. The students were given no information during their undergraduation course, even though the curriculum has the discipline of first aid. The dentist are supposed to develop actions so that such knowledge meets the needs of the future physical education practitioners.