On the formation features and some material properties of the coating formed by laser cladding of a nicrbsi self-fluxing alloy

In the present paper, the influence of laser cladding conditions on the powder flow conditions as well as the microstructure, phases, and microhardness of a Ni-based self-fluxing alloy coating is studied. The formation regularities of a coating microstructure with different cladding conditions as well as patterns of element distribution over the coating depth and in the transient zone are defined. The microhardness distribution patterns by depth and length of a coating for various laser cladding conditions have been studied. It was found that the laser beam speed, track pitch, and the distance from the nozzle to the coated surface influence the changes of the coating microstructure and microhardness

ВЛИЯНИЕ СПОСОБА ОХЛАЖДЕНИЯ ЗОНЫ РЕЗАНИЯ НА УСЛОВИЯ СТРУЖКООБРАЗОВАНИЯ

The paper considers an influence of a cutting zone cooling method on the chip shape and thickening ratio while turning R35 steel with the hardness of НВ 1250 МРа. Cutting with various types of cooling - dry, compressed air and emulsion fog has been investigated in the paper. OPORTET RG-2 emulsol with emulsion concentration of 4% has been used as an active substation. Cutting tool is a turning cutter with a changeable square plate SNUN120408 made of Р25 hard alloy with multilayer wear-resistant coating, upper titanium nitride layer. Front plate surface is flat. Range of cutting speeds - 80-450 m/min, motions - 0,1-0,5 mm/rev, emulsion flow - 1,5-3,5 g/min and compressed air - 4,5-7,0 m3/h, cutting depth - 1,0 mm. In order to reduce a number of single investigations it is possible to use plans based on ЛПх-sequences.It has been shown that the method for cutting zone cooling exerts significant influence on conditions for chip formation. Regression equation describing influence of machining conditions on Ка-chip thickening ratio has been obtained in the paper. The range of cutting modes is extended while using emulsion fog for cooling. In the process of these modes chip is formed in the shape of short spiral fragments or elements. Favourable form of chips is ensured while using the following rate of emulsion - not more than 2 g/min. The investigations have made it possible to determine conditions required for cooling emulsion fog. In this case it has been observed minimum values in chip thickening ratio and chip shape that ensures its easy removal from cutting zone. While making dry turning values of Ка is higher not less than 15 % in comparison with other methods for cutting zone cooling.В статье рассмотрено влияние способа охлаждения зоны резания на форму и коэффициент утолщения стружки при точении стали R35 твердостью 1250 МПа. Исследовали резание при охлаждении всухую, сжатым воздухом и эмульсионным туманом. В качестве активной субстанции использовали эмульсол OPORTET RG-2, концентрация эмульсии - 4 %. Режущий инструмент - токарный резец со сменной квадратной пластиной SNUN120408 из твердого сплава Р25 с многослойным износостойким покрытием, верхний слой - нитрид титана, передняя поверхность пластины - плоская. Диапазон скоростей резания - 80-450 м/мин, подач - 0,1 -0,5 мм/об, расходов эмульсии - 1,5-3,5 г/мин и сжатого воздуха - 4,5-7,0 м3/ч. Глубина резания - 1,0 мм. Для сокращения количества единичных исследований можно использовать планы, базирующиеся на ЛПт-последовательностях.Показано, что способ охлаждения зоны резания оказывает существенное влияние на условия стружкообразования. Получено уравнение регрессии, описывающее влияние условий обработки на коэффициент утолщения стружки Ка.При охлаждении эмульсионным туманом расширяется диапазон режимов резания, при которых формируется стружка в виде коротких фрагментов спирали или элементная. Благоприятная форма стружки обеспечивается при расходе эмульсии не более чем 2 г/мин. В результате исследований определены условия охлаждения эмульсионным туманом, при которых наблюдаются наименьшие значения коэффициента утолщения стружки и форма стружки, обеспечивающая ее легкое удаление из зоны резания. При точении всухую значения Ка больше не менее чем на 15 % по сравнению с другими способами охлаждения зоны резания

ФОРМИРОВАНИЕ ТОПОГРАФИИ ПОВЕРХНОСТИ ДЕТАЛЕЙ ИЗ СТАЛИ 12ХН3А ПРИ ИГЛОФРЕЗЕРОВАНИИ

Topography formation of 12ХН3А steel part surface is considered at needle milling. As a result of the executed researches mathematical models are developed when needle milling modes influence on the formation of the wide nomenclature of the parameters describing geometrical structure of the machined surface according to ISO-3274:1997 and ISO 4287:1998. Рассмотрено формирование топографии поверхности деталей из стали 12ХН3А при иглофрезеровании. В результате выполненных исследований разработаны математические модели влияния режимов иглофрезерования на формирование широкой номенклатуры параметров, характеризующих геометрическую структуру обработанной поверхности в соответствии с ISO-3274:1997 и ISO 4287:19

МОДЕЛИРОВАНИЕ ФОРМИРОВАНИЯ КАЧЕСТВА ПОВЕРХНОСТИ ЗАГОТОВОК ИЗ ЧУГУНОВ ПРИ ИГЛОФРЕЗЕРОВАНИИ

Formation of topography, geometrical structure and micro-hardness of pig iron billet surface is considered in the paper. Mathematical models pertaining to formation of the above-mentioned characteristics of surface quality according to parameters of machining regime have been developed on the basis of the executed investigations.Рассмотрено формирование топографии, геометрической структуры и микротвердости поверхности заготовок из чугунов. На основании проведенных исследований разработаны математические модели формирования указанных характеристик качества поверхности в зависимости от параметров режима обработки

3D Finite Element Modelling of Cutting Forces in Drilling Fibre Metal Laminates and Experimental Hole Quality Analysis

Machining Glass fibre aluminium reinforced epoxy (GLARE) is cumbersome due to distinctively different mechanical and thermal properties of its constituents, which makes it challenging to achieve damage-free holes with the acceptable surface quality. The proposed work focuses on the study of the machinability of thin (~2.5 mm) GLARE laminate. Drilling trials were conducted to analyse the effect of feed rate and spindle speed on the cutting forces and hole quality. The resulting hole quality metrics (surface roughness, hole size, circularity error, burr formation and delamination) were assessed using surface profilometry and optical scanning techniques. A three dimensional (3D) finite-element (FE) model of drilling GLARE laminate was also developed using ABAQUS/Explicit to help understand the mechanism of drilling GLARE. The homogenised ply-level response of GLARE laminate was considered in the FE model to predict cutting forces in the drilling process

Energetic particle influence on the Earth's atmosphere

This manuscript gives an up-to-date and comprehensive overview of the effects of energetic particle precipitation (EPP) onto the whole atmosphere, from the lower thermosphere/mesosphere through the stratosphere and troposphere, to the surface. The paper summarizes the different sources and energies of particles, principally galactic cosmic rays (GCRs), solar energetic particles (SEPs) and energetic electron precipitation (EEP). All the proposed mechanisms by which EPP can affect the atmosphere are discussed, including chemical changes in the upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks, the global electric circuit and cloud formation. The role of energetic particles in Earth’s atmosphere is a multi-disciplinary problem that requires expertise from a range of scientific backgrounds. To assist with this synergy, summary tables are provided, which are intended to evaluate the level of current knowledge of the effects of energetic particles on processes in the entire atmosphere

On the Features of Composite Coating, Based on Nickel Alloy and Aluminum–Iron Bronze, Processed by Direct Metal Deposition

In recent years, additive manufacturing technologies have become increasingly widespread with the most intensive development being direct metal deposition (DMD), alloys, and ceramic materials on a metal substrate. This study shows the possibilities of the effective formation of coatings, based on heterogeneous metal alloys (Ni-based alloy and Fe-Al bronze) deposited onto 1045 structural steel. Changes in the microhardness, the microstructure, and the tribological properties of the composite coating, depending on the laser spot speed and pitch during DMD processing, have been considered. It was revealed that if the components of the composite coating are chosen correctly, there are possible DMD conditions ensuring reliable and durable connection between them and with the substrate

On Investigating the Microstructural, Mechanical, and Tribological Properties of Hybrid FeGr1/SiC/Gr Metal Matrix Composites

In recent years, studies of different properties of hybrid metal matrix composites, as well as very detailed issues, have been published. In this article, ready-made iron, graphite, and silicon carbide powders were used to produce the base material and composites. An analysis of some microstructural and mechanical properties, as well as the tribological behavior of metal matrix composites (MMCs), based on FeGr1 sintered material with the single and hybrid addition of a silicon carbide and graphite was undertaken. During the study, the flexural and compressive strength of MMCs were analyzed and changes of the momentary coefficient of friction, the temperature of friction, as well as wear rates of the MMCs tested were monitored. Based on the results, it was revealed that wear rates decreased 12-fold in comparison to the base material when SiC or SiC + Gr were added. Further research into MMCs with ceramic particle additives is proposed

The analyze of friction conditions on a rake face when finish turning on the base of chip thickness changes

Przedstawiono wyniki wykorzystania teoretycznych wzorów do obliczeń średnich współczynników tarcia na powierzchni natarcia ostrza skrawającego w warunkach obróbki wykończeniowej. Rozpatrywane wzory zweryfikowano z wynikami badań doświadczalnych. Podstawowym wskaźnikiem określającym warunki tarcia w strefie skrawania jest grubość wióra. Na jej podstawie obliczono kąty poślizgu i tarcia na powierzchni natarcia. Proponowana metoda została wykorzystana do analizy procesu toczenia stali 45, R35, 40H, NC6, duraluminium PA6 oraz molibdenu w różnych warunkach. W zależności od składu chemicznego i właściwości fizykomechanicznych materiału obrabianego, zastosowania powłok przeciwzużyciowych oraz warunków chłodzenia, wartości średnich współczynników tarcia na powierzchni natarcia można zmniejszyć od 10 do 20%.In the paper, the results of the analysis of theoretical equations to calculate middle coefficients of friction on a tool rake face during finish cutting are described. Equations viewed were compared with experimental results. The base magnitude that characterises friction conditions into the cutting zone is uncut chip thickness. Using its values, one may calculate shear angles and friction angles on tool rake face. The proposed method was used to analyse the process of steels 45, R35, 40H, NC6, duralumin PA6 and molybdenum turning with different conditions. Depending on chemical composition and physical-mechanical properties of material machined, using antiwear coatings and cooling conditions, middle coefficients of friction on tool rake face may be decreased from 10 to 20%

Influence of some parameters of the electromachining on the state of the surface layer of elements of tool steel

Described in the paper investigations were aimed at determining the influence of the amperage, the time of discharge impulse and breaks between impulses in EDM processing of tool steel 56NiCrMoV7 on some parameters of the geometric surface structure. One stated that values of the impulse amperage and the time of discharge impulse had a significant influence on the state of the worked surface. The increase of these process parameters not only considerably worsening the surface roughness, but also generates existence of microcracks as a result of high temperatures in the discharges zone. Times of breaks between impulses didn't indicate the influence on parameters of the surface roughness and its topography.W procesie obróbki elektroerozyjnej(EDM) usunięcie materiału spowodowane jest wyładowaniami elektrycznymi pomiędzy elektrodą roboczą a przedmiotem obrabianym. Naddatek jest usuwany z przedmiotu obrabianego w wyniku oddziaływania zjawisk fizycznych spowodowanych wyładowaniami elektrycznymi. Najbardziej efektywnym obszarem zastosowania obróbki elektroerozyjnej jest obróbka materiałów o małej skrawalności. Na podstawie analizy literaturowej można stwierdzi, że największy wpływ na wydajno procesu DM i jako powierzchni obrobionej wielu materiałów konstrukcyjnych mają parametry elektryczne oraz niektóre inne parametry procesu. Celem badań było określenie wpływu natężenia prądu, czasu impulsu wyładowania i przerw między impulsami na wybrane parametry używane do opisu stanu powierzchni stali narzędziowych i nierdzewnych