Основные параметры процесса и характеристики покрытий как критерии оценки эффективности метода анодного микродугового оксидирования

The article is devoted to the evaluation of the feasibility and efficiency of modernization of the microarc oxidation process (MAO) by changing the conditions and parameters of sparking, as well as the selection of criteria for assessing the quality and predicting the service properties of formed ceramic-like coatings. The predominant role in changing the nature of structure formation and in ensuring the predicted quality and properties of the oxidized alloy is played by the intensity of sparking, which occurs in the process of electric discharges migrating along the treated surface of the object immersed in the electrolyte. Intensity of sparking determines the conditions for obtaining equidistant coatings: the less stochastic the nature of sparking around the oxidized part is, the more evenly and rapidly the thickness of the formed coating increases and its density is higher. These considerations allowed us offering the option of upgrading method of the anode MAO (AMAO), wherein only the anodic component of the current, causing thereby obtaining thin coatings with extensive porosity by stabilizing the process of arcing through the use of the system of quasi cathodes in the electrolysis bath. In this study, we consider the possibility of controlling the parameters of coatings obtained by the AMDO method in its standard and upgraded versions, by fixing in real time the nature of the distribution of spark discharges, indirect evidence of which is the change in the current density over time and the uniformity of the thickness of the coatings created. Taking into account the influence of micro-arc oxidation on the structural and qualitative features of formed layers, it was assumed that the surface of the coating obtained by the modernized method should have a higher quality, one of the indicators of which is a more smooth and uniform relief. Thus, another criterion for the efficiency of the modernized process can serve as amplitude and step parameters of roughness, which, without allowing an objective assessment of the microprofile of the formed coating, can give more extensive information about the nature of the increase in its thickness and quality changes, determining the level of operational capabilities of metal objects with such a coating.Статья посвящена оценке целесообразности и эффективности модернизации процесса микродугового оксидирования (МДО) посредством изменения условий и параметров искрения, а также выбору критериев оценки качества и прогнозирования служебных свойств формируемых керамикоподобных покрытий. Преимущественную роль в изменении характера структурообразования и в обеспечении прогнозируемого качества и свойств оксидируемого сплава играет интенсивность искрения, которое возникает в процессе электрических разрядов, мигрирующих по обрабатываемой поверхности погруженного в электролит объекта. Интенсивность искрения определяет условия получения равнотолщинных покрытий: чем менее стохастичен характер искрения вокруг оксидируемой детали, тем более равномерно и быстро прирастает толщина формируемого покрытия и выше его плотность. Эти соображения позволили предложить вариант модернизации метода анодного МДО (АМДО), отличающегося наличием только анодной составляющей тока, обусловливая тем самым получение тонких покрытий с разветвленной пористостью посредством стабилизации процесса искрения за счет использования системы квазикатодов в электролизной ванне. В настоящем исследовании рассматриваются возможности контроля параметров покрытий, полученных методом АМДО в его стандартном и модернизированном вариантах, посредством фиксации в режиме реального времени характера распределения искровых разрядов, косвенным свидетельством чего является изменение плотности тока во времени и равномерность толщины созданных покрытий. Учитывая влияние характера микродугового оксидирования на структурные и качественные особенности формируемых слоев, было предположено, что поверхность покрытия, полученного модернизированным методом, должна иметь более высокое качество, одним из показателей, которого является более сглаженный и равномерный рельеф. Таким образом, еще одним критерием эффективности модернизированного процесса могут служить амплитудные и шаговые параметры шероховатости, которые, не позволяя провести объективную оценку микропрофиля сформированного покрытия, могут дать более обширную информацию о характере прироста его толщины и изменении качества, определяя в итоге уровень эксплуатационных возможностей металлических объектов с таким покрытием

КАК «НАУЧИТЬ» СПЛАВЫ МАГНИЯ ПРОТИВОСТОЯТЬ ЭКСПЛУАТАЦИОННЫМ РИСКАМ

The paper studies regularities and mechanisms of structure and phase formation in the surface layers of magnesium alloys when they are processed by method of micro-arc oxidation [MAO]. It has been determined that the same specific features of structure formation, namely: existence of a thin dense inner sublayer and a thicker outer sublayer with developed porosity are common for all types of coatings on the surface of magnesium and aluminum alloys. Such structural state of a protective coating can not be considered as a guaranteed protection against operational impacts, taking into account the fields of their primary application that is aviation construction, automotive construction, instrumentation, building construction, etc. The paper has analyzed the effect of alkaline electrolytes with varying chemical composition due to additions of sodium fluoride or potassium on the structure and properties of these alloys as well as on the level of basic performance characteristics of the layers formed in such electrolytes. On the basis of the analysis a conclusion has been made that it is possible to extend their life-span under operational conditions. It has been revealed that the existing techniques and methods for process control of MAO aluminum and magnesium alloys, particularly processing modes and technological equipment capacity determine a nature of structure formation and changes in a phase composition of the formed coatings.Изучены закономерности и механизмы структурои фазообразования в поверхностных слоях магниевых сплавов при их обработке методом микродугового оксидирования. Определено, что для всех видов покрытий на поверхности магниевых и алюминиевых сплавов характерны одинаковые особенности структурообразования: наличие тонкого плотного внутреннего подслоя и более толстого с развитой пористостью наружного. Такое структурное состояние защитного покрытия не является гарантированной защитой объектов от эксплуатационных воздействий, учитывая области их преимущественного использования – авиа-, автомобиле-, приборостроение, строительство и т. п. Проанализировано влияние щелочных электролитов с изменяющимся химическим составом за счет добавок фторидов натрия или калия на структуру и свойства указанных сплавов, а также на уровень основных эксплуатационных характеристик слоев, формируемых в таких электролитах. На основании этого сделан вывод о возможности продления их ресурса в эксплуатационных условиях. Выявлено, что существующие приемы и способы управления процессом микродугового оксидирования алюминиевых и магниевых сплавов, в частности режимы обработки и мощность технологического оборудования, определяют характер структурообразования и изменение фазового состава формируемых покрытий

РОЛЬ УЛЬТРАЗВУКА В МЕХАНИЗМАХ АНОДНО-КАТОДНЫХ ВЗАИМОДЕЙСТВИЙ ПРИ ЭЛЕКТРОИСКРОВОМ ЛЕГИРОВАНИИ

The paper reveals results of investigations on mass transfer kinetics and dynamics of coating formation while using integral electrospark alloying method with additional ultrasonic exposure at different stages of formation. Nowadays, a classical method for electrospark alloying with hard-alloy anodes and impulse AC voltage frequency on the vibration exciter coil from 20 to 1600 Hz has been mainly used for application of protective and strengthening coatings within permissible thickness and characteristics. The key aspect of ultrasonic exposure application (frequency 22–44 kHz) during electrospark alloying is the possibility to increase further thickness of coatings to be formed even after reaching a brittle fracture threshold of the coating material. Methodology of the executed research activity has been based on integrated studies (gravimetric, metallographic, X-ray diffraction and electron microscopic) of coatings which are to be formed through compositions produced while using method of high-energy hot compaction and a “refractory carbide (WC) and a binding material“ system in the form of alloy based on nickel from the series of “colmonoy” Ni – Ni3B system which is alloyed with additions of copper and silicon. The initial surface treatment within ultrasonic frequency range (22–44 kHz) contributes to a noticeable increase in the mass transfer rate, which is primarily determined by chemical composition and thermodynamic stability of anodes. It is due to surface activation in the process of its preliminary deformation at ultrasonic frequency which creates additional conditions for striking of a spark.The final ultrasonic treatment improves coating quality due to its additional forging that leads to an increase of its structure homogeneity and density.Приведены результаты исследований кинетики массопереноса и динамика формирования покрытий интегральным способом электроискрового легирования с дополнительным ультразвуковым воздействием на разных стадиях их формирования. В настоящее время для нанесения защитно-упрочняющих покрытий в пределах допустимых толщин и характеристик в основном применяется классический метод электроискрового легирования с использованием твердосплавных анодов и частотой импульсного переменного напряжения на катушке вибровозбудителя от 20 до 1600 Гц. Главной особенностью применения ультразвукового воздействия (частота 22–44 кГц) в процессе электроискрового легирования является возможность дальнейшего наращивания толщины формируемых покрытий даже после достижения порога хрупкого разрушения материала покрытия. Методика проводимой работы базировалась на комплексных гравиметрических, металлографических, рентгеноструктурных и электронно-микроскопических исследованиях формируемых покрытий на основе композиций, изготовленных методом высокоэнергетического горячего прессования, и системы «тугоплавкий карбид (WC) – связка» в виде сплава на основе никеля из серии «колмоной» системы Ni – Ni3B, легированной добавками меди и кремния. Первоначальная обработка поверхности в диапазоне ультразвуковых частот 22–44 кГц способствует заметному возрастанию скорости массопереноса, которая определяется прежде всего химическим составом и термодинамической устойчивостью анодов. Это объясняется активацией поверхности в процессе ее предварительного деформирования с ультразвуковой частотой с созданием дополнительных условий для возникновения искрового разряда. Завершающая ультразвуковая обработка улучшает качество покрытия вследствие его дополнительной проковки, приводя к увеличению однородности его структуры и повышению ее плотности

Clinical and molecular characterization of diffuse large B-cell lymphomas with 13q14.3 deletion.

Background: Deletions at 13q14.3 are common in chronic lymphocytic leukemia and are also present in diffuse large B-cell lymphomas (DLBCL) but never in immunodeficiency-related DLBCL. To characterize DLBCL with 13q14.3 deletions, we combined genome-wide DNA profiling, gene expression and clinical data in a large DLBCL series treated with rituximab, cyclophosphamide, doxorubicine, vincristine and prednisone repeated every 21 days (R-CHOP21). Patients and methods: Affymetrix GeneChip Human Mapping 250K NspI and U133 plus 2.0 gene were used. MicroRNA (miRNA) expression was studied were by real-time PCR. Median follow-up of patients was 4.9 years. Results: Deletions at 13q14.3, comprising DLEU2/MIR15A/MIR16, occurred in 22/166 (13%) cases. The deletion was wider, including also RB1, in 19/22 cases. Samples with del(13q14.3) had concomitant specific aberrations. No reduced MIR15A/MIR16 expression was observed, but 172 transcripts were significantly differential expressed. Among the deregulated genes, there were RB1 and FAS, both commonly deleted at genomic level. No differences in outcome were observed in patients treated with R-CHOP21. Conclusions: Cases with 13q14.3 deletions appear as group of DLBCL characterized by common genetic and biologic features. Deletions at 13q14.3 might contribute to DLBCL pathogenesis by two mechanisms: deregulating the cell cycle control mainly due RB1 loss and contributing to immune escape, due to FAS down-regulation

Clinical and molecular characterization of diffuse large B-cell lymphomas with 13q14.3 deletion

Background: Deletions at 13q14.3 are common in chronic lymphocytic leukemia and are also present in diffuse large B-cell lymphomas (DLBCL) but never in immunodeficiency-related DLBCL. To characterize DLBCL with 13q14.3 deletions, we combined genome-wide DNA profiling, gene expression and clinical data in a large DLBCL series treated with rituximab, cyclophosphamide, doxorubicine, vincristine and prednisone repeated every 21 days (R-CHOP21). Patients and methods: Affymetrix GeneChip Human Mapping 250K NspI and U133 plus 2.0 gene were used. MicroRNA (miRNA) expression was studied were by real-time PCR. Median follow-up of patients was 4.9 years. Results: Deletions at 13q14.3, comprising DLEU2/MIR15A/MIR16, occurred in 22/166 (13%) cases. The deletion was wider, including also RB1, in 19/22 cases. Samples with del(13q14.3) had concomitant specific aberrations. No reduced MIR15A/MIR16 expression was observed, but 172 transcripts were significantly differential expressed. Among the deregulated genes, there were RB1 and FAS, both commonly deleted at genomic level. No differences in outcome were observed in patients treated with R-CHOP21. Conclusions: Cases with 13q14.3 deletions appear as group of DLBCL characterized by common genetic and biologic features. Deletions at 13q14.3 might contribute to DLBCL pathogenesis by two mechanisms: deregulating the cell cycle control mainly due RB1 loss and contributing to immune escape, due to FAS down-regulatio

HOW TO MAKE MAGNESIUM ALLOYS BE RESISTANT TO OPERATIONAL RISKS

The paper studies regularities and mechanisms of structure and phase formation in the surface layers of magnesium alloys when they are processed by method of micro-arc oxidation [MAO]. It has been determined that the same specific features of structure formation, namely: existence of a thin dense inner sublayer and a thicker outer sublayer with developed porosity are common for all types of coatings on the surface of magnesium and aluminum alloys. Such structural state of a protective coating can not be considered as a guaranteed protection against operational impacts, taking into account the fields of their primary application that is aviation construction, automotive construction, instrumentation, building construction, etc. The paper has analyzed the effect of alkaline electrolytes with varying chemical composition due to additions of sodium fluoride or potassium on the structure and properties of these alloys as well as on the level of basic performance characteristics of the layers formed in such electrolytes. On the basis of the analysis a conclusion has been made that it is possible to extend their life-span under operational conditions. It has been revealed that the existing techniques and methods for process control of MAO aluminum and magnesium alloys, particularly processing modes and technological equipment capacity determine a nature of structure formation and changes in a phase composition of the formed coatings

ROLE OF ULTRASOUND IN MECHANISMS OF ANODE-CATHODE INTERACTIONS DURING ELECTROSPARK ALLOYING

The paper reveals results of investigations on mass transfer kinetics and dynamics of coating formation while using integral electrospark alloying method with additional ultrasonic exposure at different stages of formation. Nowadays, a classical method for electrospark alloying with hard-alloy anodes and impulse AC voltage frequency on the vibration exciter coil from 20 to 1600 Hz has been mainly used for application of protective and strengthening coatings within permissible thickness and characteristics. The key aspect of ultrasonic exposure application (frequency 22–44 kHz) during electrospark alloying is the possibility to increase further thickness of coatings to be formed even after reaching a brittle fracture threshold of the coating material. Methodology of the executed research activity has been based on integrated studies (gravimetric, metallographic, X-ray diffraction and electron microscopic) of coatings which are to be formed through compositions produced while using method of high-energy hot compaction and a “refractory carbide (WC) and a binding material“ system in the form of alloy based on nickel from the series of “colmonoy” Ni – Ni3B system which is alloyed with additions of copper and silicon. The initial surface treatment within ultrasonic frequency range (22–44 kHz) contributes to a noticeable increase in the mass transfer rate, which is primarily determined by chemical composition and thermodynamic stability of anodes. It is due to surface activation in the process of its preliminary deformation at ultrasonic frequency which creates additional conditions for striking of a spark.The final ultrasonic treatment improves coating quality due to its additional forging that leads to an increase of its structure homogeneity and density