PHASE COMPOSITION, SUBSTRUCTURE AND RESIDUAL MACROSTRESSES IN THE SURFACE LAYER OF A TAPE OBTAINED BY ELECTRIC CONTACT WELDING

Методами рентгенографии и электронной микроскопии исследован поверхностный слой чугуна ВЧ50-2 после его обработки электроконтактной приваркой. В качестве присадочного материала использовалась лента из стали 50ХФА. Применялись технологии обработки с созданием промежуточного слоя из никелевого порошка ПГН-12Н-01 и без него. Получены результаты о фазовом составе, субструктуре и остаточных напряжениях. Исследуемая система состоит из фаз a - Fe и у - Fe . Параметры субструктуры (микродеформации и измельчение блоков) имеют одинаковые значения для различных режимов электроконтактной приварки. Остаточные напряжения носят растягивающий характер и уменьшаются при создании промежуточного слоя из никелевого порошкового материала. Основной механизм их образования - термические воздействия на материал, обрабатываемый электроконтактной приваркой. Установлено, что после электроконтактной приварки ленты могут образовываться трещины, их ориентация преимущественно параллельно обрабатываемой поверхности обусловлена наличием большого градиента температур. The surface layer of DI50-2 cast iron after its processing by electric contact welding has been investigated by methods of X-ray diffraction and electron microscopy. A 50HVA steel strip was used as a filler material. Processing technologies were used with the creation of an intermediate layer of nickel powder PC-12N-01 and without it. Results on phase composition, substructure and residual stresses are obtained. The system under study consists of a-Fe and у-Fe phases. Substructure parameters (microstrain and block refinement) have the same values for different modes of electrical contact welding. Residual stresses are of a tensile nature and decrease when an intermediate layer of nickel powder material is created. The main mechanism of their formation is thermal effects on the material processed by electrocontact welding. Cracks may form after electrical contact welding of the tape. They are oriented mainly parallel to the surface to be treated and are due to the presence of a large temperature gradient.

Obtaining microdispersed iron-nickel powder in the process of electrochemical processing of VNZh type heavy tungsten alloys

The process of electrochemical processing of the VNZh type heavy tungsten alloy (wt. %: 80 W, 16 Ni, 4 Fe) under the action of direct and alternating current of industrial frequency in an ammonia-alkaline solution has been investigated. It was found, that the process is accompanied by the transition of tungsten from the alloy to the solution and the formation of a microdispersed powder, based on iron and nickel.

X-ray Fluorescence Spectroscopy Features of Micro- and Nanoscale Copper and Nickel Particle Compositions

The study is devoted to X-ray fluorescence spectroscopy (XRF) features of micro- and nanosized powder mixtures of copper and nickel. XRF is a high accuracy method that allows for both qualitative and quantitative analysis. However, the XRF measurement error due to the size of the studied particles is not usually taken into account, which limits the use of the method in some cases, such as analysis of Ni-Cu mixtures and coatings. In this paper, a method for obtaining copper and nickel nanoparticles was investigated, and the XRF of powder compositions was considered in detail. The initial micro- and nanoparticles of copper and nickel were studied in detail using SEM, TEM, XRD, and EDX. Based on experimental data, calibration curves for copper-nickel powder compositions of various sizes were developed. According to the results, it was experimentally established that the calibration curves constructed for nanoscale and microscale powders differ significantly. The presented approach can be expanded for other metals and particle sizes.

On microstructural and mechanical properties of 21-4-N nitronic steel joint developed using microwave energy

In the current experimental work, an effort has been made to explore the feasibility of fusion joints of 21-4-N nitronic steel employing microwave heating. These fusion joints were developed inside a domestic microwave applicator operating at 900 W. Microwave energy was used to fabricate the joints in hybrid heating mode by converting electromagnetic energy into heat at 2.45 GHz. Charcoal and SiC plates were used as susceptor and separator, respectively, and nickel powder was used as the interface material. The developed joints were characterized for their microstructural and mechanical properties. The microstructures indicate a complete fusion of nickel interfacing powder with the faying surfaces. XRD results show the formation of metallic nitrides and carbide phases (Cr2N, Fe3N, and Fe2C) and the FeNi phase at the weld zone. Furthermore, the observed average tensile strength of the fusion joints was approximately 61% of base metal. The reduction in the stress and elongation compared to the base metal were 38.67% and 12.68%, respectively. The average microhardness of the microwave joints was monitored as 407 ± 69.27 HV. The results indicate the feasibility of fusion joints of nitronic steel using microwave energy.

Possibilities of Utilization of Waste Materials in Production of Electrically Conductive Composites on Silicate Basis

The electrical conductivity of concrete can be achieved by adding steel wires or functional fillers. Commonly used fillers are nanotubes, carbon black, nickel powder and so on. These fillers are expensive, but there is a possibility to use waste materials. This is the subject of this experiment. The conductive properties of conductive sand, sludge from the wire drawing process, iron grinding dust waste and waste carbon were verified. From these fillers, waste carbon showed the best electrical properties (impedance). The impedance of the waste carbon was 0.31 Ω and the impedance of the cement composite containing 70% of the weight of waste carbon was less than 670 Ω.

ACOUSTIC PERFORMANCES OF METAL SAMPLES MANUFACTURED BY ADDITIVE TECHNOLOGIES

Porous materials (PMs) have been widely used since the development of powder metallurgy. PM samples are obtained by various methods, while the structure varies from sample to sample. Deviation from a given structure leads to a deviation of the specified properties up to 30%, including acoustic. Selective laser melting (SLM), allows to obtain samples with a low structural deviation (up to 13%) in a wide porosity range P=0.3-0.7. An increase in the sound absorption coefficient and the expansion of the frequency range allows to use such samples in noise reduction units’ designs. Nine samples with different porosity and cell shape were obtained by the SLM method with the use of AlSi10Mg aluminum powder obtained by gas atomization and BB751P nickel powder obtained by plasma centrifugal spraying. The porosity of the samples (P) varied in the range (0.3–0.7), the diameter was D = 34.5 mm, and the height varied in the range of 15–45 mm. The acoustic characteristics comparison of traditional PMs with porous fused material (PFM) by the sound absorption index shows that PM, as a rule, are superior to PFM, while it is approximately equal to porous cast