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1

Effect of Welding Technique and Thermal Heatment Parameters on Abrasive Wear of Steel S355

Konat Łukasz, Białobrzeska Beata

Tribologia

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2022

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nr 3

25--38

EN

The paper presents technological and microstructural aspects of welding and post-weld heat treatment of the S355 constructional steel welded joints. It was found that welding this steel resulted in a wide heataffected zone with diverse microstructures conducive to lower abrasive-wear resistance and worse mechanical characteristics of the steel. In this connection, the welding technique of the S355 steel was suggested, as well as conditions and parameters of the post-weld heat treatment, which made it possible to obtain – in the entire welded joint area – the microstructures characterised by high mechanical properties and increased resistance to abrasive wear. It was shown that the suggested set of technological operations applied to the S355 steel resulted, under laboratory conditions, in a significant increase of relative abrasive-wear resistance, determined by the abrasion test with use of the of loose aloxite 90.

PL

W pracy przedstawiono technologiczne i mikrostrukturalne aspekty wykonywania i obróbki cieplnej połączeń spawanych stali konstrukcyjnej S355. W wyniku przeprowadzonych badań stwierdzono, że zastosowanie do łączenia tej stali procesów spawalniczych prowadzi do powstawania szerokiej strefy wpływu ciepła, charakteryzującej się zróżnicowanymi zmianami mikrostrukturalnymi, sprzyjającymi obniżeniu odporności na zużywanie ścierne oraz pogorszeniu charakterystyki wytrzymałościowej rozpatrywanej stali. W związku z tym, zaproponowano optymalną technologię spawania stali S355 oraz warunki i parametry postobróbki cieplnej, prowadzących do uzyskania w całym obszarze połączenia spawanego mikrostruktur odznaczających się wysokimi parametrami mechanicznymi oraz podwyższoną odpornością na procesy zużycia ściernego. Wykazano, iż przedstawiony w stosunku do stali S355 zakres operacji technologicznych w warunkach laboratoryjnych skutkował znacznym podwyższeniem względnej odporności na zużywanie ścierne, wyznaczonej w warunkach ścierania w obecności luźnego ścierniwa – elektrokorund 90.

2

Investigations of the structure and hardness of dissimilar steel-to-aluminum joints made using laser welding technology

Misiura Karolina, Konieczny Jarosław, Labisz Krzysztof, Boris Renata

Transport Problems

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2022

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T. 17, z. 1

73--86

EN

Since welding technology is currently used to assemble the frame of driver’s seats, it is important to develop laser welding technology for steel and aluminium. For this reason, the purpose of the present work was to examine the structure and selected properties of aluminium-steel joints using the example of an EN AW-6060 aluminium alloy and DC04 low-alloy steel welded in laser technology. Overlapping joints were made, weld type -following the hole laser welding method -laser beam (LB) using a high power disk laser (TRUMPF TruDisk3302), in which the active medium is a yttrium-aluminium crystal (YAG). Metallographic microstructure investigations were carried out using a light microscope from Carl Zeiss - Observer Z1m, and the weld microstructures were investigated using an SEM Supra 35 microscope, also from Carl Zeiss. The chemical composition analysis in micro-areas was carried out using an X-ray energy dispersion spectrometer from EDAX, which was a part of the SEM Supra 35. The hardness of the substrate material and the welded area was measured following the Vickers method using an FM-ARS 9000 micro hardness tester from Tokyo, Japan. It was found that there is a potential for commercial use of laser welding to make a low-carbon steel-aluminium alloy joint. During the formation of the weld in its microstructure, intermetallic compounds of the FexAly type were created, which significantly reduced the mechanical and plastic properties of the joint. The hardness of the weld created wasabout seven times higher than that of DC04 carbon steel. The choice of laser welding parameters (primarily, laser power and beam speed) significantly impacted the weld structure and properties.

3

Influence of sodium and potassium formate on the ASR reactivity of granite aggregate

Antolik Aneta

Structure and Environment

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2022

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Vol. 14, no. 3

69--75

EN

Use of de-icing agents is necessary in winter to maintain appropriate quality of road and airport surfaces. Formate or acetate de-icing agents are safer for aircraft and the environment than the commonly used sodium chloride, but may cause an alkali-silica reaction in concrete. The study investigated the influence of sodium formate and potassium formate on the occurrence of ASR (alkali-silica reaction) in mortars with granite aggregate. Accelerated mortar-bar tests at 80°C using various de-icing agents were performed and detailed studies of the SEM-EDS microstructure were carried out.

PL

Stosowanie środków odladzających jest niezbędne do zimowego utrzymania odpowiedniej jakości betonowych nawierzchni drogowych i lotniskowych. Środki odladzające na bazie mrówczanów lub octanów są bezpieczniejsze zarówno dla środowiska, jak i statków powietrznych niż powszechnie stosowany chlorek sodu, jednak mogą wywoływać reakcję alkaliczno-krzemionkową kruszywa w betonie. W pracy analizowano wpływ mrówczanu sodu i mrówczanu potasu na potencjał wystąpienia ASR (alkali-silica reaction) w zaprawach z kruszywem granitowym. Przeprowadzono badania ekspansji w 80°C z zastosowaniem różnych środków odladzających oraz przeprowadzono szczegółowe badania mikrostruktury SEM-EDS.

4

Determination of twist drill bits wear: the effect of the composition and structure of the steels

Prałat Karol, Krupińska Andżelika, Ochowiak Marek, Włodarczak Sylwia, Matuszak Magdalena, Ciemnicka Justyna, Koper Artur, Wójcicka Karolina

Polish Journal of Chemical Technology

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2022

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Vol. 24, nr 3

8--13

EN

The aim of the study was to relate the infl uence of the chemical composition, structure, and basic properties as hardness of the tested drill bits on resistance to their wear. The chemical composition of the drill bit was investigated using the electric excitation emission spectrometry method and EDS microanalysis. Metallographic specimens were prepared and observed to determine the structure of each tool. Hardness tests were carried out on the shank and the working part of the tools. Material wear tests were carried out on the basis of measuring the wear of the drill bit flank. It has been shown that the appropriate selection of the chemical composition and heat treatment has a signifi cant impact on the wear resistance of cutting tools, which directly translates into their quality.

5

Strukturalne aspekty korozji zmęczeniowej ocynkowanych elementów złącznych

Lachowicz Maciej B., Lachowicz Marzena M.

Ochrona przed Korozją

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2022

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nr 5

140--145

PL

W pracy przedstawiono wyniki badań mikrostrukturalnych zerwanej śruby stosowanej w sprężonych złączach doczołowych. Celem badań była ocena wpływu mikrostruktury powłoki cynkowej na proces korozji. Stwierdzono, że eksploatacji elementów ocynkowanych w środowisku korozyjnym towarzyszy zarodkowanie pęknięć w powłoce cynkowej. Powstałe pęknięcia stają się karbami spiętrzającymi naprężenia, co w warunkach oddziaływań obciążeń mechanicznych może ułatwiać inicjację pęknięć zmęczeniowych. W konsekwencji część z nich rozwija się w pęknięcia w podłożu stalowym, stanowiące przedłużenie pęknięć zainicjowanych w powłoce cynkowej. Ich obecność zmniejsza długość pęknięcia wymaganą do osiągnięcia krytycznego wymiaru prowadzącego do dalszego rozprzestrzeniania się pęknięcia na całym przekroju stalowego elementu. Pęknięcia propagują w głąb materiału w obszarze wrębów gwintu, które są makroskopowymi koncentratorami naprężeń w śrubie. Dowodzi to także istotnej roli naprężeń w dalszym rozprzestrzenianiu się tych mikropęknięć.

EN

The paper presents the results of microstructural tests of a broken bolt used in prestressed butt joints. The aim of the research results presented in this paper is to emphasize the role of the microstructure of the zinc coating on the corrosion process. It was found that the exploitation of galvanized elements in a corrosive environment is accompanied by nucleation of cracks in the zinc coating. The resulting cracks become notches that accumulate stresses, which, under the influence of mechanical loads, may facilitate thei nitiation of fatigue cracks. Consequently some of them develop into cracks in the steel substrate, which are extensions of the cracks initiated in the zinc coating. They reduce thecrack length required to achieve a critical dimension leading to further crack propagation over the entire cross section of the steel member. Cracks propagate deep into the material in the area of the thread grooves, which are macroscopic stress concentrators in the bolt. It also proves the important role of stress in the further propagation of these microcracks.

6

Porównanie mikrostruktury i odporności na korozję powłok natryskiwanych metodą HVOF (high velocity oxy fuel) na podłoże ze stopu magnezu

Jaworska Justyna, Gruszka Magdalena, Nabrdalik Monika, Marcinkowski Marcin, Mikołejko Wojciech, Augustyn Ewelina, Jonda Ewa, Maciej Artur, Kiljan Anna

Ochrona przed Korozją

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2022

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nr 4

112--123

PL

Stopy magnezu ze względu na korzystny stosunek niskiej masy do dobrych własności mechanicznych coraz powszechniej są stosowane w przemyśle. Przeszkodę w ich aplikacji może stanowić reaktywność chemiczna magnezu, a więc jego wysoka podatność na korozję. Powłoki natryskiwane cieplnie metodą HVOF (high velocity oxy fuel) pozwalają wytworzyć szczelną barierę pomiędzy materiałem podłoża a środowiskiem, dzięki czemu mogą stanowić skuteczną ochronę stopów magnezu. W artykule przedstawiono wyniki badań mikrostruktury oraz wybranych własności dwóch powłok natryskiwanych przy wykorzystaniu komercyjnych proszków WC-Co i WC-Cr3C2-Ni metodą HVOF na podłożu ze stopu magnezu AZ91. Celem pracy było porównanie mikrostruktury, wybranych własności oraz odporności na korozję wytworzonych powłok. Na podstawie wyników badań mikroskopowych stwierdzono, że powłoki charakteryzują się zwartą mikrostrukturą, a twarde cząstki WC oraz Cr3C2 są równomiernie rozłożone w całej objętości powłoki. Powłoka WC-Co charakteryzuje się ponadto wyższą odpornością korozyjną oraz mikrotwardością, jednak cechuje ją mniejsza wydajność natryskiwania i chropowatość w porównaniu z powłoką WC-Cr3C2-Ni.

EN

Due to the promising ratio of low weight to good mechanical properties, magnesium alloys are more and more widely used in industry. An obstacle in their application may be the chemical reactivity of magnesium, and therefore its high susceptibility to corrosion. Thermal sprayed coatings with the HVOF (high velocity oxy fuel) method allow creating a tight barrier between the base material and the environment, which can effectively protect magnesium alloys. The article presents the results of research on the microstructure and selected properties of two sprayed coatings with the use of commercial WC-Co and WC-Cr3C2-Ni powders using the HVOF method on the substrate made of AZ91 magnesium alloy. The work aimed to compare the microstructure, selected properties, and corrosion resistance of the produced coatings. Based on the results of the metallographic research, it was found that the coatings are characterized by a dense microstructure, and the hard particles of the WC and Cr3C2 are evenly distributed throughout the entire volume of the coating. Also the WC-Co coating is characterized by higher corrosion resistance and microhardness however, it has a lower spray efficiency and roughness compared to the WC-Cr3C2-Ni coating.

7

Wpływ przyspieszonego starzenia na mikrostrukturę i wybrane właściwości mechaniczne profili z kompozytów polimerowych zbrojonych łuskami zbóż

Kozikowska Ewelina, Sudoł Ewa

Materiały Budowlane

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2022

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nr 9

76--79

PL

Analizowano wpływ czynników atmosferycznych na przebieg starzenia kompozytów polimerowych zbrojonych włóknami lignocelulozowymi, które zostały pozyskane z łusek roślin uprawnych. Poddanie profili kompozytowych procesowi starzenia wyraźnie zmienia morfologię powierzchni. Analiza mikrostruktury powierzchni zewnętrznych uwidoczniła przetopienia wierzchniej warstwy osnowy polimerowej prowadzące do odsłonięcia powierzchni cząstek wypełniacza. Przeprowadzone badania wykazały najlepsze właściwości użytkowe profili z dodatkiem łusek owsa w stanie wyjściowym oraz po starzeniu, których właściwości były porównywalne z komercyjnymi profilami zbrojonymi łuskami ryżowymi.

EN

The influence of atmospheric factors on ageing of polymer composites reinforced with lignocellulose fibers has been analysed. Three natural fibers obtained from the husks of cultivated plants: rice, oat, millet husk were used as fillers. The microscopic analysis of the surfaces revealed melting of the top layer of the polymer matrix, leading to the exposure of the filler particles. The carried out mechanical tests showed the best properties for profiles with oat hulls in the initial state and after ageing, whose properties were comparable to those of commercial profiles reinforced with rice hulls.

8

Podstawowe właściwości geopolimerów z dodatkiem odpadu ceramicznego

Chuczun Aleksandra, Rakowski Bartosz, Gosk Edyta, Kalinowska-Wichrowska Katarzyna

Materiały Budowlane

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2022

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nr 8

80--83

PL

W artykule przedstawiono podstawowe właściwości geopolimerów z dodatkiem miału ceramicznego, tj.: wytrzymałość na zginanie i ściskanie, nasiąkliwość wagową, gęstość objętościową. Wykonano analizę SEM kompozytów i badania chemiczne surowców. Przyjęto stałą zawartość dodatku odpadowego, zmienną temperaturę wygrzewania i zawartość aktywatora. Wyniki wskazują na korzystny wpływ dodatku miału ceramicznego na badane cechy kompozytów.

EN

The article presents the basic properties of geopolymers with the use of ceramic fines, i.e. flexural and compressive strength, water absorption, bulk density. SEM analysis of composites and chemical tests of research raw materials were performed. A constant content of waste additive, a variable curing temperature and activator content were assumed. The results show a beneficial effect of the addition of ceramic fines on the examined properties of the composites.

9

Odporność profili budowlanych z kompozytów polimerowych zbrojonych łuskami zbóż na grzyby domowe

Sudoł Ewa, Kozikowska Ewelina, Goron Maria

Materiały Budowlane

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2022

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nr 9

70--75

PL

Analizowano odporność profili z kompozytów PVC z napełniaczem z pulweryzowanych łusek owsa, prosa i ryżu na działanie na grzybów domowych. Wyroby z łuskami owsa i ryżu wykazały porównywalną podatność na działanie Coniophora puteana, Gloeophyllum trabeum oraz Coriolus versicolor, ale mniejszą niż kompozyt z łuskami prosa. Coniophora puteana wykazał największy stopień rozwoju grzybni i zmienił morfologię powierzchni profili. Ekspozycja na działanie grzybów w środowisku mokrym skutkowała zmniejszeniem wytrzymałości na zginanie i modułu sprężystości, największym w przypadku kompozytu zbrojonego łuskami prosa. Kluczowy był wpływ samego środowiska mokrego. Mikroorganizmy nieznaczenie zmieniły właściwości przy zginaniu.

EN

The resistance to fungi of oat, millet and rice husks reinforced PVC composite profiles was analysed. Products with oat and rice husks showed comparable susceptibility to Coniophora puteana, Gloeophyllum trabeum and Coriolus versicolor, lower than the composite with millet husks. Coniophora puteana showed the highest degree of mycelium growth, changing the morphology of the profile surface. Exposure to fungi in a wet condition caused a decrease in flexural strength and modulus of elasticity, the greatest in the case of millet husks reinforced composite. The influence of the wet conditions itself was crucial. The microorganisms slightly changed the bending properties.

10

Ocena właściwości zapadowych lessowego podłoża gruntowego

Kokoszka Wanda

Materiały Budowlane

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2022

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nr 11

126--128

PL

Atrakcyjność gospodarcza i turystyczna obszarów lessowych sprawia, że są one intensywnie wykorzystywane w celu realizacji inwestycji budowlanych, zarówno kubaturowych, jak i liniowych. Warunki podłoża budowlanego zbudowanego z utworów lessowych są jednak uznawane za niekorzystne przede wszystkim z powodu dużej wrażliwości na zmiany zawilgocenia. W pracy przedstawiono problematykę procesów deformacyjnych w tych gruntach z uwzględnieniem analizy mikrostrukturalnej. Przeanalizowano zastosowanie wybranych kryteriów pośrednich i bezpośrednich do oceny właściwości zapadowych na przykładzie badania lessów z rejonu Rzeszowa.

EN

The economic and tourist attractiveness of loess areas means that they are intensively used for construction investments, both cubature and linear. However, the conditions of the construction substrate made of loess formations are considered unfavorable mainly due to high sensitivity to changes in moisture. The paper presents the problems of deformation processes in these soils, taking into account the microstructural analysis. The application of selected direct and indirect criteria for the assessment of collapsing properties has been analyzed on the example of loess research in the Rzeszów region.

11

The microstructures of in-situ synthesized TiC by Ti-CNTs reaction in Cu melts

Xu Xuexia, Wang Yong, Wang Qing, Dong Guozhen, Li Wenbin, Li Guowei, Lv YaDong, Zhang Jin, Ding Haimin

Materials Science Poland

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2022

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Vol. 40, No. 1

145--158

EN

In order to study the influence of the carbon nanotubes (CNTs) as a source of carbon on the microstructure of in-situ synthesized TiC in Cu melts, CNTs and Ti powders were introduced into melted Cu to prepare TiC-reinforced Cu matrix composites. The influence of Ti/C ratio and Si on the microstructures and properties of the composites were also examined. It is found that CNTs can be effectively wetted through the Ti-C reaction and successfully introduced into Cu melt to synthesize TiC. In examining the changes in Ti/C ratio, it was found that an increase in the Ti content may result in the decrease of TiC agglomeration and improvement of TiC dispersion, while simultaneously causing an increase in the TiC particle size. Besides, while the addition of Si into Ti-CNTs mixture can also improve the distribution of TiC, the effect is weak compared with that of increasing the content of Ti. It was also found that the highest hardness (238.8 HV) is achieved by the Cu-Ti-C composite with the highest Ti/C ratio, while the electrical conductivities of all the prepared composites are relatively low, which should be due to the insufficient reaction between Ti and CNTs.

12

Hardfacing of mild steel with wear-resistant Ni-based powders containing tungsten carbide particles using powder plasma transferred arc welding technology

Appiah Augustine Nana Sekyi, Bialas Oktawian, Żuk Marcin, Czupryński Artur, Konadu Sasu David, Adamiak Marcin

Materials Science Poland

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2022

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Vol. 40, No. 3

42--63

EN

This study explores the use of powder plasma transferred arc welding (PPTAW) as a surface layer deposition technology to form hardfaced coatings to improve upon the wear resistance of mild steel. Hardfaced layers were prepared using the PPTAW process with two different wear-resistant powders: PG 6503 (NiSiB + 60% WC) and PE 8214 (NiCrSiB + 45% WC). By varying the PPTAW process parameters of plasma gas flow rate (PGFR) and plasma arc current, hardfaced layers were prepared. Microscopic examinations, penetration tests, hardness tests, and abrasive wear resistance tests were carried out on the prepared samples. Hardfacings prepared with PG 6503 had a hardness of 46.3–48.3 HRC, while those prepared with PE 8214 had a hardness of 52.7–58.3 HRC. The microhardness of the matrix material was in the range of 573.3–893.0 HV, while that of the carbides was in the range of 2128.7–2436.3 HV. The abrasive wear resistance of the mild steel was improved after deposition of hardfaced layers by up to 5.7 times that of abrasion-resistant heat-treated steel, Hardox 400, having a nominal hardness of approximately 400 HV. The hardness and wear resistance were increased upon addition of Cr as an alloying element. Increasing the PGFR increased the hardness and wear resistance of the hardfacings, as well as increasing the number of surface cracks. Increasing the plasma transferred arc (PTA) current resulted in hardfacings with fewer cracks but lowered the wear resistance.

13

Effect of shot peening on corrosion resistance of additive manufactured 17-4PH steel

Świetlicki Aleksander, Walczak Mariusz, Szala Mirosław

Materials Science Poland

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2022

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Vol. 40, No. 3

135--151

EN

Components produced by additive manufacturing (AM) via direct metal laser sintering (DMLS) have typical as-fabricated surface defects. As a result, surface properties of AM products should be modified to increase their strength, anti-wear behavior, and at the same time ensure their high corrosion resistance. Surface modification via shot peening (SP) is considered suitable for AM of engineering devices made of 17-4PH (X5CrNiCuNb16-4) stainless steel. The objective of this study was to determine the effect of three types of peening media (CrNi steel shot, glass, and ceramic beads) on the corrosion resistance of specimens of DMLS 17-4PH stainless steel. Results demonstrated that SP caused steel microstructure refinement and induced both martensite (α) formation and retained austenite (γ) reduction. 17-4PH specimens peened showed the increase in surface hardness of 255, 281, and 260 HV0.2 for ceramic, glass, and steel, respectively. DMLS 17-4PH specimens modified by SP exhibited different surface morphology, hardness, and microstructure and thus, these properties affect corrosion performance. The results implied that steel shot peened with steel shot showed the highest resistance to corrosion processes (Icorr= 0.019μA/cm2), slightly worse with glass (Icorr= 0.227μA/cm2) and ceramics (Icorr= 0.660μA/cm2) peened. In the case of ceramic and glass beads, it was possible to confirm the presence of the above-mentioned particles in the surface layer after SP.

14

An experimental investigation of wire breakage and performance optimisation of WEDM process on machining of recycled aluminium alloy metal matrix composite

Kannan P. R., Periasamy K., Pravin P., Vinod Kumaar J. R.

Materials Science Poland

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2022

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Vol. 40, No. 3

12--26

EN

In this research, a novel aluminium metal matrix composite (AMMC) was developed using recycled aluminium alloy as a matrix with 5% alumina as reinforcement. The machining experiments were conducted by varying the input parameters such as voltage (Vs), wire feed rate (Fw), current (Ip), pulse on time (ONT) and pulse off time (OFFT), on wire breakage. The effect of voltage level and wire breakage frequency was analysed. The parameter combinations for machining the slot of size 5 mm width and 10 mm height with high machining rate (MR) and less surface roughness (Ra) were analysed using the Criteria Importance Through Intercriteria Correlation (CRITIC) and simple additive weighting (SAW) methods. The wire breakage frequency is lesser at minimum peak current. The optimal parameter combination for higher MR and lower Ra is found to be at 30 V, 7 mm/min, 30 A, 120 μs (ONT) and 70 μs (OFFT). Analysis of variance (ANOVA) is performed to understand the significant factors affecting the WEDM process. ANOVA results predict that wire feed rate and voltage contribute 47.82% and 21.23%, respectively, to MR; and pulse on time shows a 23.06% influence on surface roughness. Scanning electron microscopy (SEM) was used to ascertain the pattern of wire breakage in WEDM, and based on the results obtained from employing this technique, it is inferred that the erosion and breakage of the wire are not instantaneous and that a cone shape is formed on the either portion of the wire.

15

Role of Si on machined surfaces of Al-based automotive alloys under varying machining parameters

Razin Ahmed Asif, Ahammed Dewan Salsabil, Nur Maglub Al, Kaiser Mohammad Salim

Journal of Mechanical and Energy Engineering

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2022

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Vol. 6, No 1

43--52

EN

A morphological change due to Si contend into Al-based automotive alloys has been conducted on the characterization of machined surfaces in terms of roughness, temperature, chips formation as well as microstructure evaluation under different machining conditions. For this experiment, a shaper machine with HSS single point V-shaped cutting tool is used at different cutting speeds and depths of cut. The experimental results show that the surface roughness of the alloys decreases with the cutting speed and depth of cut but it is more prominent in the case of the cutting speed. This is because of a high cutting speed, which is more associated with the higher temperature and softening the work material leading to better surface finish. Higher Si added alloys also exhibit a better surface finish because the sample content is different fine and hard intermetallic due to ageing treatment, which also makes the alloys more brittle. For brittle and higher hardness, it produces a higher temperature during machining. During machining, relatively curly and short chips are formed by the high Si added alloy because of its low elongation properties. The fracture surfaces of higher Si added alloy display more crack propagation obtained by plate-like Si rich intermetallic.

16

A Simulation and Experimental Investigation of the Thermal Characteristics of Refractory Bricks Produced Using Fireclay and Agroforestry Wastes

Obidiegwu Eugenia Obiageli, Esezobor David Ehigie, Mgbemere Henry Ekene, Odili Cletus Chiosa

Journal of Casting & Materials Engineering

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2022

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Vol. 6, no. 2

45--57

EN

Manufacturing and processing industries usually consume large quantities of materials and energy in the course of their operations. The energy supplied for high-temperature processes are used partially for the actual technical process and between 30 to 40% of the energy escapes through the walls of the reactor into the atmosphere, leading to a high degree of thermal inefficiency and fuel consumption. This paper studies the thermal behaviour of insulating refractory bricks produced from a blend of fireclay and agroforestry wastes. The fireclays used were obtained from Ukpor deposit in Anambra State (Latitude 5.95°N, Longitude 6.92°E), Osiele deposit in Abeokuta, Ogun State (Latitude 7.18°N, Longitude 3.45°E) and Kankara Katsina State (Latitude 11.93°N, Longitude 7.41°E), all of which are in Nigeria. Samples were prepared with various weight percentages (60–100 wt.%) clays and (0–40 wt.%) of agroforestry waste, with grain sizes between 212 and 600 µm. Raw materials and the developed refractory bricks were characterised using appropriate standard techniques. The chemical, mineralogical constituents and phases present in the microstructure were examined. Physical and thermo-mechanical properties were investigated. The insulating refractory bricks developed have porosity of 78.83% , cold crushing strength (CCS) 3.144 kN/m2 and thermal conductivity 0.04–0.046 W/(m∙K) that compare favourably with imported bricks 75–85%, 2.756 kN/m2 and 0.049 W/(m∙K) in both physical, mechanical and thermal properties respectively. The reason is that the agroforestry waste used (coconut shell), served to create the pores that improve insulation after burning. Also the ash that remains serves as reinforcement to improve the mechanical properties. The thermal behaviour of the bricks was studied using Finite Element Method and shows a strong correlation with the experimental findings. This indicates that the produced insulating bricks have the thermal properties required for insulation of furnaces.

17

HA-ZnO-Fe3O4 composite manufactured by wet powder metallurgy process for implant applications

Gupta Ruchi, Agarwal Mayank, Singh Vinay Pratap

Composites Theory and Practice

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2022

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R. 22, nr 1

40--43

EN

A hydroxyapatite (HA) based biocompatible and bioactive composite is an appropriate choice for bio-implants. This experimental work presents the influence of ZnO and Fe3O4 on the microstructure of HA-ZnO-Fe3O4 composites synthesized by the wet powder metallurgy process. These composites were characterized using SEM, energy-dispersive X-ray spectroscopy (EDS), and XRD. The obtained results showed the effect of the addition of Fe3O4 on the interface formation, which is exhibited by interconnected pores and sintered neck in the micrographs. The observed porosity helps to enhance the required osseointegration for the fixation of implants with human bones.

18

Aggregate Type Influence on Microstructural Behavior of Concrete Exposed to Elevated Temperature

Belkadi Ahmed Abderraouf, Kessal Oussama, Bensalem Sara, Aggoun Salima, Amouri Chahinez, Khouadjia Mohamed Lyes Kamel

Civil and Environmental Engineering Reports

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2022

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Vol. 32, no. 1

19--42

EN

Exposure of concrete to high temperatures affects its mechanical properties by reducing the compressive strength, bending… etc. Factors reducing these properties have been focused on by several studies over the years, producing conflicting results. This article interested an important factor, that is the type of aggregates. For this, an experimental study on the behavior of concrete based on different types of aggregates: calcareous, siliceous and silico-calcareous subjected to high temperatures. In addition, the particle size distribution of the aggregates was chosen to be almost identical so that the latter does not affect the behavior of the concrete. Aggregates and concrete samples were subjected to a heating/cooling cycle of 300, 600 and 800°C at a speed of 1°C/ min. The mechanical and physical properties of concrete before and after exposure to high temperatures were studied. In addition, a microstructural study using a scanning electron microscope and a mercury porosimeter was performed. Thus, a comparative study between various researches on the mechanical properties of concrete exposed to high temperatures containing different types of aggregates was carried out. The compressive strength test results showed that the concrete based on siliceous aggregates (C-S) has better mechanical performance up to 300°C. However, above 300°C, the compressive strength decreases faster compared to calcareous-based concrete (C-C). According to the mercury porosimeter test, at 600°C, C-SC and C-S concretes have the highest number of pores compared to C-C concretes. The microstructure of concrete at high temperatures was influenced mainly by the aggregate’s types and the paste-aggregate transition zone. This study reinforces the importance of standardizing test procedures related to the properties of concrete in a fire situation so that all the results obtained are reproducible and applicable in other research.

19

Wpływ rodzaju kruszywa na opóźnione powstawanie ettringitu

Owsiak Zdzisława

Cement Wapno Beton

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2022

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R. 27, nr 2

144--151

PL

Przeprowadzone badania miały na celu oznaczenie wpływu rodzaju kruszywa na równoczesne występowanie reakcji wodorotlenków sodu i potasu z krzemionką w kruszywie i opóźnionego powstawania ettringitu. Stosowano piasek lub kruszywo wapienne oraz kruszywo zawierające 6% opalu, o uziarnieniu od 0,5 do 1,0 mm. Przygotowano zaprawy z tymi rodzajami kruszywa i z cementem portlandzkim, zawierającym 1,2% Na2Oe i 4,5% SO3, które dojrzewały w 90°C i w wodzie. Badania potwierdziły duży wpływ rodzaju kruszywa, na rozszerzalność spowodowaną opóźnionym powstawaniem ettringitu. Po tych warunkach dojrzewania kruszywo wapienne w znacznym stopniu zmniejszyło ekspansję zaprawy, spowodowaną opóźnionym powstawaniem ettringitu, natomiast miało znacznie mniejszy wpływ na ekspansję beleczek, spowodowaną przez reakcję wodorotlenku potasu z opalem. Obserwacje mikrostruktury zaprawy wykazały, że żel sodowo-potasowo-wapienny, a także ettringit otaczający ziarna kruszywa, są odpowiedzialne za ekspansję w przypadku piasku z dodatkiem opalu.

EN

The studies carried out aimed to define the influence of the aggregate type on the simultaneous occurrence of the alkali-silica reaction and delayed ettringite formation. In their composition, sand or calcium aggregate and aggregates containing 6% opal with graining of 0.5 to 1.0 mm, were used. Mortars from each type of aggregate and Portland cement containing 1.2% Na2Oe and 4.5% SO3 were prepared, and then cured in water at 90°C. Studies have shown a great influence of the type of aggregate on the expansion caused by the delayed ettringite formation. In this case, the calcium aggregate visibly reduces the expansion of a mortar caused by delayed ettringite formation, while it has a much smaller influence on the expansion of the bars, caused by the potassium reaction with opal. Microstructure observations have shown that sodium-potassium-calcium silicate gel and ettringite around the aggregate grains, are responsible for expansion in the case of sand with opal addition.

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The Influence of Aluminum Content on the Porosity, Microstructure, and Mechanical Properties of Powder Metallurgy Steels

Sazegaran Hamid, Bahari Hasan, Naserian-Nik Ali Mohammad, Khorramshahi Farhad

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

105--111

EN

An experimental study was performed to assess the influences of aluminum content on the porosity, microstructure and mechanical properties of powder metallurgy steels. Optical microscope equipped with the image processing software and the scanning electron microscope were employed to study the microstructure of investigated specimens. In order to find mechanical properties of specimens, Vickers hardness and compression tests were conducted. By increasing the aluminum content (from 0 to 4 wt. %), the porosity increases (from 6.01% to 8.43%). The microstructure of specimens contains aluminum phase distributed between the boundaries of agglomerated iron particles, ferrite, and pearlite. By increasing the aluminum content, stress-strain curves shift significantly downwards, and the modulus of elasticity, elongation, yield stress, and Vickers hardness reduce from 1.82 to 0.86 GPa, 32.1 to 17.8%, 138.1 to 28.2 MPa, and 127.7 to 26.8 HV, respectively.