This study investigates the high-temperature oxidation behavior of novel SiW-xAl (x: 0-4 wt%) cast irons developed for high-performance applications. The methodology combines thermodynamic modeling using the CALPHAD approach with experimental oxidation tests conducted in air and COQ-containing atmospheres at temperatures between 750 degrees C and 850 degrees C. Results demonstrate that increasing aluminum content enhances oxidation resistance by promoting the formation of dense Al-rich oxide layers, which inhibit iron oxide growth and reduce oxide scale thickness. Thermogravimetric analyses reveal that SiW-xAl cast irons exhibit superior oxidation resistance compared to conventional SiMo cast iron, with resistance further improving as aluminum content increases. Surface and cross-sectional examinations confirm the development of protective oxide layers, primarily FeAlQO4, which limit oxygen diffusion. These findings suggest that SiW-xAl cast irons are promising candidates for high-temperature components, offering enhanced durability and potential to replace traditional ductile cast irons in demanding environments.

Abstract This study investigates the microstructural, surface, and mechanical properties of DP450 steel under varying annealing and galvannealing conditions, emphasizing the effects of dew point and galvannealing furnace (GAF) temperature. Microscopic analyses showed a predominantly ferritic matrix with secondary martensite and bainite phases within DP450. Surface oxidation was examined at dew points of −25 °C, 0 °C, and +15 °C. Lower dew points favored external selective oxidation of manganese and chromium, while higher dew points promoted internal oxidation, affecting coating quality. Depth profiling confirmed that dew point variations influenced oxide layer thickness and composition. Galvannealed coatings mainly consisted of delta and zeta intermetallic phases, with Fe diffusion and alloying strongly depended on dew point and GAF temperature. Low temperatures and dew points caused insufficient alloying, heterogeneous coatings, increased zeta phase, and surface irregularities. Raising dew point and temperature enhanced Fe diffusion, producing uniform delta phase coatings with smoother surfaces. Mechanical tests linked coating friction and powdering behavior to phase composition and surface morphology. Optimizing dew point and GAF temperature balances oxidation and Fe–Zn reaction kinetics, resulting in coatings that meet automotive standards for Fe content, phase ratios, and mechanical performance.

Abstract This study presents a comprehensive structural characterization of medieval glazed ceramics from Toprakkale and Osmaniye regions in Upper Plain Cilicia, Türkiye. Utilizing advanced non-destructive techniques, the research investigates ceramic body, slip, and glaze phases to elucidate production technologies and raw material selections. Results reveal that Toprakkale sherds possess relatively homogeneous aluminosilicate matrices with moderate silica and low flux oxide contents, indicative of controlled raw material preparation and firing protocols. Conversely, Osmaniye sherds display broader compositional variability, characterized by higher silica, calcareous, and alkali oxide contents, reflecting the incorporation of diverse temper materials and less standardized manufacturing processes. Mineralogical analyses show that Toprakkale sherds experienced higher firing temperatures, promoting the formation of diopside phases, while Osmaniye ceramics exhibit incomplete calcite decomposition, suggesting moderate firing conditions. Glaze compositions demonstrate significant variations in lead oxide content highlighting differing fluxing strategies and technological choices. The study underscores regional technological diversity and adaptation to local resources, contributing valuable insights into medieval ceramic production and cultural interactions within the northeastern Mediterranean basin.

Zinc complexes have considerable impact on human health and environment especially on aquatic wildlife. One of the main sources of zinc release to the environment is worn rubber particles from tires. Environmental footprint of zinc oxide during production, ecological and economical concerns have prompted the researchers to reduce its use in rubber formulations. Rubber compounds used in the tread, which is the part of the tire in contact with road, must have high wear resistance. In order to determine the wear performance, laboratory wear tests need to be carried out prior to road tests. In the present study, a tread compound recipe based on SBR/BR blend is designed using conventional and composite ZnO materials having CaCO 3 as core. Wear behavior of the control and trial compounds prepared with these ZnO materials are tested at room temperature by using Lambourn test instrument. Wear rates and wear energies are calculated using the weight loss data at different slip rates. Based on the wear performance of the trial compounds as well as their cure and mechanical properties, it can be concluded that composite ZnO materials are good candidates to replace the conventional activators in rubber compounds to provide environmental and economic gains.

In this study, Cu-6Ni-1.5Si-xAl (x = 0 and 0.15 wt%) alloys are manufactured as billet materials by casting and their metallurgical and physical properties are characterized. Aluminum modified alloy is obtained also by a powder metallurgical (PM) route and its structural properties are determined to be compared with the cast materials. The findings indicate that (i) solidified alloys have distributed nickel silicides (27.01 %) embedded in alpha-Cu(Ni,Si) solid solution, (ii) the addition of aluminum increases the amount of silicides (29.09 %) in the solidified matrix and reduces both the grain size and the secondary dendrite arm spacing, (iii) although PM alloy has similar microstructural features as cast alloys, it exhibits the highest hardness (159 HV1) due to both finer grain structure and better distribution of silicides, (iv) both impurity and porosity have a determining effect on the electrical conductivity (27-32 % IACS, International Annealed Copper Standard) values of the alloys.

In this study, the degradation occurring on the surface of the electrodes used in resistance spot welding of hot dip galvanized and galvannealed low carbon steels are examined and the life of the electrodes are tested. Several characterization studies are carried out on the surface and cross-sections of CuCrZr-based electrodes, following the life tests that are carried out according to SEP 1220 standard, and it is observed that a more convex degradation surface is formed on the electrode surface used in the welding of galvannealed steel compared to the galvanized one. This geometry indicates that the induced current is more stable. Depending on the increase in the number of spots, coating type and the amount of convexity, it is determined that the phases formed on the electrode surface also differ. Although the coating type has no significant effect on the welding strength value and no significant difference is observed in the maximum current values, a longer life is determined in the electrode used for the welding of galvannealed steel. It has been identified that the dominant mechanism affecting electrode life is the coating type, which is directly related to electrode degradation.

Monolayer (CrN, AlTiN) and bilayer (CrN/AlTiN) coatings are formed on the surface of conventional heat-treated and gas-nitrided X45CrMoV5-3-1 tool steel via Cathodic Arc Physical Vapor Deposition (CAPVD), and the adhesion characteristics and room- and high-temperature wear behavior of the coatings are compared with those of the un-nitrided ones. Scratch tests on the coatings show that the bilayer coating exhibits better adhesion behavior compared to monolayer ones, and the adhesion is further increased in all coatings due to the high load carrying capacity of the diffusion layer formed by the nitriding process. Dry friction tests performed at room temperature reveal that, among ceramic-based coatings, the coating system with a high adhesion has the lowest specific wear rate (0.06 × 10−6 mm3/N·m), and not only the surface hardness but also the nitriding process is important for reducing this rate. Studies on wear surfaces indicate that the bilayer coating structure has a tendency to remove the surface over a longer period of time. Hot wear tests performed at a temperature (450 °C) corresponding to aluminum extrusion conditions show that high friction coefficient values (>1) are reached due to aluminum transfer from the counterpart material to the surface and failure develops through droplet delamination. Adhesion and tribological tests indicate that the best performance among the systems studied belongs to the steel–CrN/AlTiN system and this performance can be further increased via the nitriding process.

Zinc oxide is considered as the most widely used activator that influences curing reaction kinetics and promotes short sulphide crosslinks to achieve higher crosslink density in rubber compounds. Besides its effect on curing process, it has beneficial effects on the physical and mechanical properties of rubber as well. However, its level should be minimized in rubber compounds because of its toxicity for human health and environment, especially on aquatic wildlife. One of the potential routes for decreasing ZnO level is to use composite ZnO materials where ZnO particles are coated. In this study, composite ZnO materials having ZnO:CaCO 3 ratio as 40:60, 60:40 and 90:10 are used in SBR/BR compounds and their effects on mechanical properties under ageing conditions are investigated and compared with the conventional white seal ZnO and active ZnO types. The findings have shown that all composite materials have no negative effect on mechanical properties under ageing conditions, thus they can be used as alternative materials to conventional activators.

Zinc complexes have a considerable impact on human health and the environment, especially on aquatic wildlife. One of the primary sources of zinc release to the environment is worn rubber particles from tires. The environmental footprint of zinc oxide (ZnO) during production, use, and landfilling has prompted researchers to reduce its use in rubber formulations due to ecological and economic concerns. In this study, composite ZnO materials where ZnO particles are coated on precipitated calcium carbonate (CaCO3) are used in styrene butadiene rubber/butadiene rubber (SBR/BR) compounds, and their performance is compared with white seal ZnO and active ZnO. Trial compounds are prepared on a laboratory scale using composite ZnO materials with ZnO:CaCO3 ratios of 40:60, 60:40, and 90:10, and control compounds with white seal and active ZnO. All compounds are tested to evaluate their curing and physico-mechanical properties. It is observed that the surface area of ZnO plays an essential role in crosslink density and, hence, compound performance. Trial materials have no negative effect on the curing and mechanical properties of the compounds. Thus, it is concluded that composite ZnO materials can be used as alternatives to both white seal ZnO and active ZnO. They have environmental and economic advantages due to their lower ZnO content. The compound recipe has the potential to be used for tire tread compounds.

In this study, AlTiN (monolayer) and CrN/AlTiN (bilayer) coatings are deposited on the surface of conventional heat-treated AISI H11 steel which is then nitrided by cathodic arc physical vapor deposition (CAPVD). Structural analyses of the coatings reveal that homogeneous, continuous, and defect-free coatings are obtained with a good adhesion on the diffusion layer of the substrate material. Considering the surface hardness, the CrN/AlTiN coating (1718 HV0.01) deposited on the surface of the heat-treated tool steel has a higher value than that of AlTiN coating (1658 HV0.01), and this hardness value is increased even more (1932 HV0.01) with the application of the nitriding process. With a contact model in which the ANSYS static structural module is operated, it is shown that CrN/AlTiN coating contributes to lower tensile stress distribution on the surface during indentation. Analysis has also revealed that bilayer coating, CrN/AlTiN, exhibits reduced deformation compared to monolayer coating, indicating enhanced mechanical strength under contact conditions. Additionally, nitriding is found to increase stress distribution, emphasizing its role in improving coating performance. It is determined that wear losses can be reduced by the high load carrying capacity provided by nitriding and the high surface hardness provided by CrN/AlTiN coating under dry friction test conditions performed against alumina as counterpart material at room temperature.

The low oxidation resistance of SiMo ductile cast irons used as exhaust manifold material at high temperatures necessitates the development of new generation ductile cast iron compositions. New alloy designs can be made using CALPHAD methodology, and solidification sequence, segregation and critical phase transformation temperatures can be determined, especially for the solidified bulk materials. Thus, in commercial practicality, castable compositions with a raised A1 temperature can be obtained. In this study, novel SiNb cast irons with varying silicon contents were developed as candidate materials for exhaust manifolds. Solidification sequence, microsegregation, phase transformations, equilibrium phases of hypereutectic compositions containing 4 to 7 wt pct Si were calculated by CALPHAD-based modeling. The bulk materials of the studied compositions were cast as Y blocks and metallurgical analyzes were carried out. Studies revealed that; (i) in the ferritic matrix of the cast irons, graphite, Nb-rich carbides and some pearlite existed, (ii) pearlite formation was due to the negative segregation of silicon and positive segregation of manganese during solidification, (iii) as silicon content increased the amount of silicon dissolved in ferrite phase increased in the solidified structure and as a result pearlite formation decreased at the cell boundaries, and amount of vermicular graphite increased, (iv) depending on the silicon content the critical A1 temperature varied between 860 °C to 1013 °C and these values were higher than that of SiMo cast iron. All these findings revealed that SiNb cast irons had phase stability at higher temperatures compared to SiMo cast iron.

Alumina powders are utilized in many industries like electronics, metallurgy optoelectronics, and fine ceramic composites. In this study, non-aqueous-based tape casting of alumina was carried out in a non-continuous single-blade tape casting machine. A slurry of alumina powder in a solvent was cast on a stationary surface with additives like dispersants, binders, and plasticizers. After the green tapes were dried, they were sintered to obtain the final desired shape. The hydraulic pressing method was used to increase the density of the alumina tapes. Layered alumina ceramics were produced at 5 different temperatures by pressureless sintering method (1450°C, 1500°C, 1550°C, 1600°C and 1650°C) for 5 h to observe the effect of sintering temperature. Results revealed the sintering conditions for obtaining translucent alumina, with the utilized slurry composition. Translucent alumina ceramics have gained importance as parts of semiconductor devices, substrates for electric parts, as heat/corrosion materials in reaction tubes and crucibles, and are used in medical equipment.

Monolayer (CrN, AlTiN) and bilayer (CrN/AlTiN) coatings were deposited on the surface of X45CrMoV5-3-1 (DIN 1.2999) tool steel by Cathodic Arc Physical Vapor Deposition (CAPVD). Adhesion of the coatings to substrate was evaluated by scratch tests which indicated that the bilayer coating exhibited better behavior over the monolayers, depending on the load applied either adhesive or cohesive failure was detected. Tribological tests conducted at room temperature (RT) revealed that coatings with better adhesion exhibited lower specific wear rate (6.4 × 10–6 mm3/N.m) and higher coefficient of friction (0.35-0.40). Examination of worn surfaces indicated that the monolayer-coated specimens displayed abrasive wear and spallation, while the bilayer-coated specimen had a smoother surface. Monolayer-coated steels had deeper wear track depths compared to the bilayer-coated material; even though the coatings had been completely removed at the end of the wear tests, the bilayer-coated material survived longer due to its adhesive characteristic. High-temperature (HT) tests were conducted at 450 °C in order to simulate the aluminum extrusion conditions, and it was found that higher coefficient of friction values above “1” was observed due to aluminum transfer to the surfaces from the counterpart material. Although cracks were present in CrN coating, only droplet delamination existed in AlTiN and CrN/AlTiN coatings. The results indicated that an integral system consisting of X45CrMoV5-3-1/CrN/AlTiN had superior adhesion and tribological performance compared to monolayer-coated tool steels.

The oxidation behavior of novel xSiNb cast irons designed for use as exhaust manifold material is studied by computational alloy thermodynamics and oxidation tests. Computational alloy thermodynamics is applied to determine the oxidation behavior of novel xSiNb cast irons (x: 4, 5, 6 and 7 wt%) designed as alternative exhaust materials to commercial SiMo ductile cast iron. In the modelling studies, the types and amounts of the oxides formed on the surface, depending on the oxygen partial pressure, are investigated at 750 and 850 degrees C and the findings reveal that as the silicon content increases the amount of Si-rich Fe2SiO4 phase increases that acts as a protective barrier. Oxidation tests are carried out in two stages to verify the modelling studies. Initially, thermogravimetric analyses are carried out at 800 degrees C to determine the oxidation kinetics of xSiNb cast irons and the results indicate that oxidation kinetics are reduced as silicon content increases. Then, oxidation tests are carried out at 750, 800 and 850 degrees C for 24 h in dry air atmosphere to characterize the oxides formed on the surfaces and cross-sections of cast irons. Characterization studies show that (i) a thinner oxide layer is formed on the surface as silicon content increases, (ii) the oxide layer consists of an outer and an inner layer, (iii) the inner layer has more silicon content compared to the outer layer. All findings indicate that xSiNb cast irons have potential for high temperature applications and can be preferred to SiMo ductile cast iron.

In this study, heat-treated and multisurface engineered DIN 1.2367 tool steel was subjected to room and elevated temperature wear tests, and the effect of nitriding on its tribological behavior was investigated. CrN, AlTiN, and CrN/AlTiN coatings with a total thickness of 2 µm were obtained by arc cathodic physical vapor deposition on conventional heat-treated and gas-nitrided steels. The white layer formed during nitriding was removed, and a diffusion layer (100 µm) was achieved in the cross section of the steel having a tempered martensitic matrix. The highest surface hardness was attained with an integral coating (CrN/AlTiN), and surface hardness increased even more after nitriding due to the formation of a multicomponent ceramic layer on top of the diffusion layer. The room temperature wear tests performed against an alumina counterpart revealed that (i) CrN/AlTiN-coated steel had the highest friction coefficient of 0.26, which further increased to 0.33 by nitriding due to the increase in shear strength, and that (ii) with increasing surface hardness, the specific wear rates (W) of the heat-treated and coated steels could be ranked as follows: WCrN/AlTiN < WAlTiN < WCrN. The wear rates decreased when nitriding was carried out prior to coating. In order to simulate the aluminum extrusion conditions, hot wear behavior of the surfaces against AA6080 alloy at 450 °C was investigated. The hot wear tests revealed that (i) high friction coefficients were reached due to the adhesive characteristic of aluminum to the surfaces, (ii) the nitrided and CrN/AlTiN-coated sample exhibited the lowest wear rate among all studied surfaces, and (iii) the film damage on the worn surfaces mostly occurred in the form of droplet delamination.

In this study, powder metallurgical Cu-Ni-Si alloys with different Ni:Si ratios are produced by cold pressing sintering (600 MPa, at 950?C for 60 min) and bulk materials are solution annealed at 950?C for 60 min, quenched in water and aged at 450?C for 60 min. A fine distribution of Ni-Si compounds embedded in a netted-free structure is formed in the matrix. Although a conductivity level of at least 22% IACS is achieved in all powder metallurgical alloys, the impurity effect is dominant and a decrease in the conductivity is detected by increasing Ni:Si ratio. However, a slight increase in electrical conductivity is achieved by the precipitation of nickel silicides in the ?-Cu matrix under aging conditions. Increasing Ni:Si ratio directly increases the hardness of the powder metallurgical matrix, and a hardness value of 73 HV0.1 is obtained for the aged alloy having the highest Ni:Si (5:1) ratio.

Abstract In this study, effect of homogenization on precipitation kinetics and mechanical properties during aging in AA7050 alloy was investigated. The billet material produced by direct chill method was homogenized at 470 °C for 12–20 h and then extruded to form T-profile. The electrical conductivity of the alloy aged at 120 and 185 °C for 0–36 h were measured and precipitation kinetics were calculated based on the relationship between increased electrical conductivity and amount of precipitates during aging. Time dependent precipitation fraction change curves using Avrami equations revealed that precipitation accelerated as the homogenization time increased due to increased nucleation and growth rates of precipitates. Peak hardness values in aging were reached depending on the increase in homogenization time, however, lower peak hardness (∼185 HV) was determined at 185 °C aging compared to the obtained ones (195–197 HV) at 120 °C aging. Depending on the increase in homogenization time, an increase trend in strength was detected in peak aged alloys. The application of longer time homogenization and subsequent aging caused an increase in strengths. The studied homogenization and aging conditions could be a useful guide for achieving the highest strength and ideal elongation values in commercial practice for the AA7050 alloy.

In this study, novel SiNb-xAl (x:0–4 wt.

Abstract In this study, the microstructural characterization of a solution annealed and quenched EN AW 6082 alloy was performed that was subjected to cold deformation (10 and 30%) and equal channel angular pressing. The findings showed that a band structure was formed, the crystallite size decreased significantly as well as that the dislocation density and stored energy increased due to severe plastic deformation. Static and dynamic precipitations in the processed alloys were characterized by thermal analyses and it was observed that precipitation sequence in heating shifted to lower temperatures due to increased kinetics caused by deformation. Increased precipitation kinetics due to severe plastic deformation could be seen in the variation of hardness during aging at 190 °C and the peak hardness of deformed alloys shifted to shorter aging times. The peak hardness of conventional heat-treated alloy was attained as 122 HV0.5 for 300 min, whereas the same hardness was achieved for an aging time of 45 min in the 30% cold-deformed alloy. By severe plastic deformation, the highest peak hardness was obtained as 130 HV0.5 after aging for 15 min. Microstructural characterization on overaged alloys indicated that the alloy having the highest stored energy had the highest tendency for recrystallization.

In this study, high-temperature oxidation behavior of ductile cast irons designed by Nb and Al addition (3.5 wt pct C, 4 wt pct Si, 1 wt pct Nb, 0 to 4 wt pct Al) is studied to develop an alloy that can perform better at elevated temperatures compared to commercial SiMo alloy. In the designed alloy, Mo is replaced by Nb as ferrite stabilizer and carbide former and has advantages compared to Mo since it does not form a network structure in the solidified matrix. Aluminum is added to the composition to inhibit the pearlite formation by causing inverse segregation of silicon that results in stabilizing ferrite and to obtain Al-rich protective oxide forms on the surfaces. Initially microstructural features of SiMo and designed alloys were examined, and modeling studies were carried out by Thermo-Calc software to determine the phases formed at high temperatures that are slightly below and above the A 1 temperatures of the alloys. Oxidation kinetics of SiMo and the designed alloys were determined by thermogravimetric analyses followed by oxidation tests at 750 °C, 800 °C and 850 °C in an air atmosphere furnace. The cross-sections and surfaces of the oxidized alloys were then characterized by microscopical studies and X-ray diffraction. The results revealed that all designed alloys exhibited better oxidation resistance at all studied temperatures than commercial SiMo alloy, and as aluminum addition increases, better performance is obtained because of the formation of Al-rich protective oxide layers. Thus, the designed alloys can be suggested as alternative exhaust manifold materials at elevated temperatures.