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

Research on emulsion mist generation in the conditions of minimum quantity cooling lubrication (MQCL)

U radu se opisuje učinak parametara stvaranja emulzijske izmaglice i udaljenosti mlaznice od kontaktne površine reznog klina s obratkom na promjer i broj kapljica dospjelih u zonu rezanja. Dati su uvjeti stvaranja emulzijske izmaglice u kojoj su sve kapljice, dovedene u zonu rezanja u datom vremenu, u to vrijeme isparile. Opisana je analiza protoka topline u MQCL metodi i dokazano je da protok zraka i udaljenost mlaznice od zone rezanja imaju najvažniji učinak na promjer kapljica.The paper presents the effect of emulsion mist generation parameters and the distance of the nozzle from the contact zone of the cutting wedge with the workpiece on the diameter and number of droplets supplied into the cutting zone. The conditions of emulsion mist generation, in which all the droplets supplied to the cutting zone in a given time, are evaporated in this time. An analysis of heat flow in the MQCL method was presented and it was proved that the air flow and the distance of the nozzle from the cutting zone have the most significant effect on the diameter of droplets

An insight into the effect surface morphology, processing, and lubricating conditions on tribological properties of Ti6Al4V and UHMWPE pairs

The effects of surface topography, processing, and environment conditions during tribological contact between Ti6Al4V titanium alloy and UHMWPE friction pairs were systematically evaluated. Hence, in this research the polyethylene samples (blocks) having a constant surface roughness were rubbed against counter-bodies (rollers) made of titanium alloy with different roughness of surfaces. The counter-samples were manufactured using either dry machining and/or minimum quantity lubrication (MQL) conditions. Such cutting conditions are harmless to humans and the environment. Simulated body fluid (SBF) and distilled water was used to simulate the tribological trials. We have noted that the lubricant applied to protect the integrity of machined parts, the rollers, have only minor impact on the tribological features of the friction pairs tested. Further, the samples produced with dry machining demonstrated a slightly lower momentary friction coefficient and temperature. In contrast, the MQL method enable reduced friction surface and significant wear accumulation. Further, it was found that the minimum and maximum values of the Sa texture parameter associated to tribological parameters do not exceed 21% and 4%, when is used dry and MQL methods, respectively. Nevertheless, the distilled water revealed a much better wear resistance when comparing to SBF, and the later one trigger as well as an accentuated wear progress with different patterns. The results of the study are important in the design of new biomedical components produced by finish turning

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

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

The tribological properties of ferrous based coatings formed using different technological methods

W artykule przedstawiono wpływ powłok na bazie żelaza o różnym składzie chemicznym, nanoszonych różnymi metodami technologicznymi oraz warunków tarcia na właściwości tribologiczne pary trącej, tj. współczynnik tarcia i intensywność zużycia elementów węzła tarcia. Materiałem, na który nakładano powłokę, była stal C45, grubość powłok znajdowała się w zakresie 0,5-0,7 mm.Plasma-sprayed coatings on the base self-fluxing alloys were investigated. Clean ferrous-based alloy P-Cr16Fe5B4Si4 was used as well as the same with the addition of TaB, MoB, and B4C powders. Fire and laser washing were used to form coatings. The thickness measurements of coatings after processing were from 0.5–0.7 mm, on the base material of steel C45. The metallographic analysis indicated that coating structure depends on the chemical composition of the powder as well as the coating technology. When using an Amsler friction-wear machine, it was determined that when dry technical friction increasingly spreads of torque of friction are observed after some minutes of work, and when oil friction torque are very stable. Additional MoB laser alloying of the coating on a base of P-Cr4Mn2B4Si2V1 powder guarantees a minimal value of the mean friction coefficient. However, the minimal value of the momentary friction coefficient was registered for the coating with additional B4C laser alloying. During dry technical friction, using a coating on a base of P-Cr4Mn2B4Si2V1 powder with additional MoB or B4C laser alloying guarantees a multiple decrease in wear intensity. The presence of oil decreases the influence of material and technology of coating on wear intensity, the difference of values is no more then 20%

On the Bonding Strength of Fe-Based Self-Fluxing Alloy Coating Deposited by Different Methods on the Steel Substrate

In the present paper, the bonding strength of Fe-based self-fluxing alloy coating deposited by plasma spraying, gluing and laser remelting and alloying on the steel substrate have been investigated. When flame melting, a globular structure is formed. Against the background of the solid solution carbide-boride phases are clearly distinguishable, between which the Fe–Fe2B and Fe–FeB eutectic colonies are situated. Laser remelting leads to the formation of metastable structures, reinforced with dendrites, consisting of alloyed Fe-α and Fe-γ. At the low laser beam speeds the coating is melted completely with the formation of a cast structure with the dendrites. When the laser beam speed is increased, the dendritic structure gets fragmented. Structures of coatings alloyed with B4C and remelted by the laser beam vary with the increase of the spot speed. The bonding strength of coating without subsequent remelting decreases by 4–5 times in comparison with remelted. The bonding strength of the reinforced glue coating has adhesive and adhesive-cohesive character. When the load increases in the coating, microcracks develop, which gradually spread to the center of the bonding surface. For plasma coatings after laser remelting without additional alloying, the maximum bonding strength is observed with the minimum laser beam speed. With increasing the laser beam speed it decreases almost 1.5 times. In glue coatings reinforced with B4C particulates by laser remelting, the bonding strength is lower by 1.2–1.4 times in comparison with plasma coating

On the bonding strength of FE-based self-fluxing alloy coating deposited by different methods on the steel substrate

In the present paper, the bonding strength of Fe-based self-fluxing alloy coating deposited by plasma spraying, gluing and laser remelting and alloying on the steel substrate have been investigated. When flame melting, a globular structure is formed. Against the background of the solid solution carbide-boride phases are clearly distinguishable, between which the Fe–Fe2B and Fe–FeB eutectic colonies are situated. Laser remelting leads to the formation of metastable structures, reinforced with dendrites, consisting of alloyed Fe-α and Fe-γ. At the low laser beam speeds the coating is melted completely with the formation of a cast structure with the dendrites. When the laser beam speed is increased, the dendritic structure gets fragmented. Structures of coatings alloyed with B4C and remelted by the laser beam vary with the increase of the spot speed. The bonding strength of coating without subsequent remelting decreases by 4–5 times in comparison with remelted. The bonding strength of the reinforced glue coating has adhesive and adhesive-cohesive character. When the load increases in the coating, microcracks develop, which gradually spread to the center of the bonding surface. For plasma coatings after laser remelting without additional alloying, the maximum bonding strength is observed with the minimum laser beam speed. With increasing the laser beam speed it decreases almost 1.5 times. In glue coatings reinforced with B4C particulates by laser remelting, the bonding strength is lower by 1.2–1.4 times in comparison with plasma coating

On the Bonding Strength of Fe-Based Self-Fluxing Alloy Coating Deposited by Different Methods on the Steel Substrate

In the present paper, the bonding strength of Fe-based self-fluxing alloy coating deposited by plasma spraying, gluing and laser remelting and alloying on the steel substrate have been investigated. When flame melting, a globular structure is formed. Against the background of the solid solution carbide-boride phases are clearly distinguishable, between which the Fe–Fe2B and Fe–FeB eutectic colonies are situated. Laser remelting leads to the formation of metastable structures, reinforced with dendrites, consisting of alloyed Fe-α and Fe-γ. At the low laser beam speeds the coating is melted completely with the formation of a cast structure with the dendrites. When the laser beam speed is increased, the dendritic structure gets fragmented. Structures of coatings alloyed with B4C and remelted by the laser beam vary with the increase of the spot speed. The bonding strength of coating without subsequent remelting decreases by 4–5 times in comparison with remelted. The bonding strength of the reinforced glue coating has adhesive and adhesive-cohesive character. When the load increases in the coating, microcracks develop, which gradually spread to the center of the bonding surface. For plasma coatings after laser remelting without additional alloying, the maximum bonding strength is observed with the minimum laser beam speed. With increasing the laser beam speed it decreases almost 1.5 times. In glue coatings reinforced with B4C particulates by laser remelting, the bonding strength is lower by 1.2–1.4 times in comparison with plasma coating