Pulsed plasma deposition of Fe-C-Cr-W coating on high-Cr-cast iron: Effect of layered morphology and heat treatment on the microstructure and hardness

Pulsed plasma treatment was applied for surface modification and laminated coating deposition on 14.5 wt%-Cr cast iron. The scopes of the research were: (a) to obtain a microstructure gradient, (b) to study the relationship between cathode material and coating layer microstructure/hardness, and (c) to improve coating quality by applying post-deposition heat treatment. An electrothermal axial plasma accelerator with a gas-dynamic working regime was used as plasma source (4.0 kV, 10 kA). The layered structure was obtained by alternation of the cathode material (T1 - 18 wt% W high speed steel and 28 wt% Cr-cast iron). It was found that pulsed plasma treatment led to substrate sub-surface modification by the formation of an 11–18 μm thick remelted layer with very fine carbide particles that provided a smooth transition from the substrate into the coating (80–120 μm thick). The as-deposited coating of 500–655 HV0.05 hardness consisted of “martensite/austenite” layers which alternated with heat-affected layers (layers the microstructure of which was affected by the subsequent plasma pulses). Post-deposition heat treatment (isothermal holding at 950 °C for 2 h followed by oil quenching) resulted in precipitation of carbides M7C3, M3C2, M3C (in Cr-rich layers) and M6C, M2C (in W-rich layers). These carbides were found to be Cr/W depleted in favor of Fe. The carbide precipitation led to a substantial increase in the coating hardness to 1240–1445 HV0.05. The volume fraction of carbides in the coating notably increased relatively to the electrode materials

Present Status in the Development of 6 MeV Heavy Ion Beam Probe on LHD

In order to measure the potential in Large Helical Device (LHD), we have been developing a heavy ion beam probe (HIBP). For probing beam, gold beam is used, which is accelerated by a tandem accelerator up to the energy of 6 MeV. The experiments for calibration of beam orbit were done, and experimental results were compared with orbit calculations. The experimental results coincided fairly with the calculation results. After the calibration of the beam orbit, the potential in plasma was tried to measure with the HIBP. The experimental data showed positive potential in a neutral beam heating phase on the condition of ne ? 5 × 10^18 m^-3, and the increase of potential was observed when the additional electron cyclotron heating was applied to this plasma. The time constant for this increase was about a few tens ms, which was larger than a theoretical expectation. In the spatial position of sample volume, we might have an ambiguity in this experiment

Поверхностные модификации износостойких сталей методами индуцирования метастабильных аустенитных структур

Surface modifications for wear resistant steels by methods of induced metastable austenite structures / Ya. А. Cheiliakh [etc. al.] // Вісник Приазовського державного технічного університету : зб. наукових праць / ПДТУ. – Маріуполь, 2013. – Вип. 26. – С. 62–70. – (Серія : Технічні науки).The problem of creation of new economical surfacing material, not containing expensive components (Ni, Mo, Nb, W and others) and new strengthening technologies for steels is quite actual and modern for many countries. One of the way of solving this problem is to develop metastable austenite conditions and realize them in the process of wear Deformation Induced Martensite γ→α′ Transformation (DIMT), accompanied with emission of carbide, carbon-nitride or inter-metallic compound of expensive phases inside the surface layer. The purpose of this work is to develop new economical (nickel free) powder surfacing materials and new technologies of surface hardening providing strain selfhardening during the wearing process for increasing characteristic and wear resistant of the surfacing parts. New ways and processes of surface modifications of metastableaustenite phase-structural states were developed: electrode-arc surfacing with powder electrodes of metastable Fe-Cr-Mn steel grades of austenite, austenite-martensite or martensite-austenite classes without application of heat treatment, combined with subsequent quenching, ageing, thermo-cyclic treatment for regulating the degree of austenite metastability (depending upon the required wear resistance and other mechanical properties); plasma, electron-beam or laser treatments with different degree of surface melting (if necessary combined with volume heat treatment) of alloyed steels of different structural classes and designation.Проблема створення нових економічних наплавлювальних матеріалів, що не містять дорогі компоненти (Ni, Мо, Nb, W та інші) і нових зміцнюючих технологій для сталей актуальні і сучасні для багатьох країн. Одним з шляхів вирішення цієї проблеми – створювати метастабільні стани аустеніту і реалізовувати в процесі зношування деформаційні мартенситні γ→α′ перетворення (ДМП), що супроводяться виділенням карбідів, карбонитридів або інших інтерменталлідних з'єднань із збагачених фаз в наплавлених шарах. Мета цієї роботи – розвивати нові економічні (безнікелеві) порошкові наплавлювальні матеріали і нові технології поверхневого зміцнення, що забезпечують ефекти деформаційного самозміцнення в процесі зношування для підвищення характеристик ізносостійкості поверхневих шарів. Отримали розвиток нові шляхи і процеси створення поверхневих модифікацій фазово-структурних станів метастабільного аустеніту: електро-дугове наплавлення порошковими електродами метастабільних Fe-Cr-Mn марок сталей аустенітного, аустенітно-мартенситного і мартенситного класів, без термічної обробки, і у поєднанні з подальшими гартуванням, старінням, термоциклічною обробкою для регулювання ступеня метастабільної аустеніту (залежного від необхідного опору зношуванню та інших механічних властивостей); плазмова, електронно-променева або лазерна обробки з різним ступенем нагріву і плавлення (при необхідності у поєднанні з регулюючою термічною обробкою) легованих сталей різних структурних класів і призначення.Проблема создания новых экономичных наплавочных материалов, не содержащих дорогие компоненты (Ni, Mo, Nb, W и другие) и новых упрочняющих технологий для сталей актуальны и современны для многих стран. Одним из путей решения этой проблемы - создавать метастабильные состояния аустенита и реализовывать в процессе изнашивания деформационные мартенситные γ→α′ превращения (ДМП), сопровождающиеся выделением карбидов, карбонитридов или других интерменталлидных соединений из обогащенных фаз в наплавленных слоях. Цель этой работы – развивать новые экономичные (безникелевые) порошковые наплавочные материалы и новые технологии поверхностного упрочнения, обеспечивающие эффекты деформационного самоупрочнения в процессе изнашивания для повышения характеристик и износостойкости поверхностных слоев. Получили развитие новые пути и процессы создания поверхностных модификаций фазово-структурных состояний метастабильного аустенита: электро-дуговая наплавка порошковыми электродами метастабильных Fe-Cr-Mn марок сталей аустенитного, аустенитно-мартенситного и мартенситного классов, без термической обработки, и в сочетании с последующими закалкой, старением, термоциклической обработкой для регулирования степени метастабильности аустенита (зависящего от требуемого сопротивления изнашиванию и других механических свойств); плазменная, электронно-лучевая или лазерная обработки с различной степенью нагрева и плавления (при необходимости в сочетании с регулирующей термической обработкой) легированных сталей различных структурных классов и назначения

日本睡眠歯科学会口腔内装置診療ガイドライン作成委員会の活動報告

Oral appliance therapy was approved by national health insurance in Japan in 2004 and oral appliances（OAs）have since been widely used in the treatment of obstructive sleep apnea（OSA）. We herein described the process of making clinical practice guidelines by the task force of the Japanese Academy of Dental Sleep Medicine as a work report. In Japan, OAs are covered by national health insurance. In consideration of the balance between medical treatment fees and the price of technical materials, we used a single-piece（monoblock）OA that advanced the mandible forward and limited mouth opening in OSA patients in Japan. The Japanese Academy of Dental Sleep Medicine（JADSM）focused on OAs frequently used for the treatment of OSA in Japan, and considered an evaluation of their effects to benecessary. Clinical practice guidelines were developed using the Grading of Recommendations, Assessment, Development, and Evaluation（GRADE）system. We recommend OAs that advanced the mandible forward and limited mouth opening for patients with OSA.However, CPAP should be used by patients for whom it has been indicated. OAs are desirable for those who cannot use CPAP（GRADE 1B, strong recommendation/quality of evidence, “Moderate quality”）. The long-term effects and side effects, OSA severity, and comorbidities of OA therapy were not examined, which represented a limitation to the present study. In future studies, the Japanese Academy of Dental Sleep Medicine plan to update clinical practice guidelines for oral appliances used in OSA

A Population of Projection Neurons that Inhibits the Lateral Horn but Excites the Antennal Lobe through Chemical Synapses in Drosophila

In the insect olfactory system, odor information is transferred from the antennal lobe (AL) to higher brain areas by projection neurons (PNs) in multiple AL tracts (ALTs). In several species, one of the ALTs, the mediolateral ALT (mlALT), contains some GABAergic PNs; in the Drosophila brain, the great majority of ventral PNs (vPNs) are GABAergic and project through this tract to the lateral horn (LH). Most excitatory PNs (ePNs), project through the medial ALT (mALT) to the mushroom body (MB) and the LH. Recent studies have shown that GABAergic vPNs play inhibitory roles at their axon terminals in the LH. However, little is known about the properties and functions of vPNs at their dendritic branches in the AL. Here, we used optogenetic and patch clamp techniques to investigate the functional roles of vPNs in the AL. Surprisingly, our results show that specific activation of vPNs reliably elicits strong excitatory postsynaptic potentials (EPSPs) in ePNs. Moreover, the connections between vPNs and ePNs are mediated by direct chemical synapses. Neither pulses of GABA, nor pharmagological, or genetic blockade of GABAergic transmission gave results consistent with the involvement of GABA in vPN-ePN excitatory transmission. These unexpected results suggest new roles for the vPN population in olfactory information processing

Three-Body Abrasive Wear-Resistance Characteristics of a 27Cr-Based 3V-3Mo-3W-3Co Multicomponent White Cast Iron with Different Ti Additions

A multicomponent white cast iron containing 5 wt.% each of Cr, V, Mo, W, and Co (MWCI) is known to have excellent wear-resistance properties due to the precipitation of some very hard carbides, such as MC, M2C, and M7C3. However, it seems possible to improve the wear resistance of MWCI by increasing the carbide volume fraction (CVF). Thus, 27 wt.% Cr based on 3 wt.% each of V, W, Mo, and Co was simultaneously added into the white cast iron. To avoid the tendency of carbides to crack due to high M7C3 precipitation levels, titanium (0–2 wt.% Ti) was also added. A rubber wheel abrasive machine test according to the ASTM G65 standard with two different abrasive particle sizes (average: 75 and 300 μm) was used to evaluate the wear characteristics of the alloy. The results show that the wear resistance of these new alloys (0Ti, 1Ti, and 2Ti) is lower than that of MWCI in small silica sand, owing to the lower hardness. However, a different condition is present in large silica sand, for which the abrasive wear resistance of MWCI is lower than that of the 0Ti and 1Ti specimens. In addition, TiC precipitation effectively refined the size of M7C3 carbides and reduced their cracking tendency. Thus, the wear resistance of 1Ti is comparable to that of 0Ti, although it has a lower hardness factor. However, the wear resistance of the alloy significantly decreased following the addition of Ti by more than 1 wt.% due to the lower hardness and CVF. Therefore, it can be said that the abrasive wear characteristics of the alloy are not only affected by the hardness, but also by the micro-structural constituents (type, size, and volume fraction of carbides) and silica sand size