Cu-4Ti alloy was solution annealed at 900 degrees C for 1 h and water-quenched followed by direct aging (variant I) or aging after 50 % cold rolling (variant II) at 450-600 degrees C for 1-420 min. Microstructure, hardness and wear properties were studied. Variant I yielded uniform beta'-Cu4Ti precipitates, reaching 240 HV after 120 min. at 500 degrees C and narrowing wear tracks to 540 mu m2 with 4 mu m penetration depths. Variant II attained 300 HV in 15 min, yet its dislocation-rich gradient microstructure promoted over-aging, beta-Cu3Ti coarsening and partial recrystallization, expanding grooves beyond 1 mm2 despite higher hardness. ANOVA confirmed temperature as dominant wear driver. Overall, variant I offers best hardness-wear compromise, whereas variant II provides only optimized short aging.

In this study, the solidification behavior of EN-GJS-400-15 ductile cast iron inoculated with bismuth-bearing systems containing Bi, La, Al, Sb, and Zr-Mn was investigated using adaptive thermal analysis. Cooling curves obtained during solidification were evaluated in terms of eutectic solidification time, eutectic interval, cooling rate, and temperature differences associated with the eutectic reaction. The graphite morphology developed after solidification was characterized by graphite nodule count, average nodule diameter, and nodularity. The results revealed that (i) variations in adaptive thermal analysis parameters were directly associated with differences in graphite characteristics and matrix phase distribution, (ii) the Bi + Bi inoculation system produced a higher cooling rate and a narrower eutectic interval, resulting in a high graphite nodule count, high nodularity, and a predominantly ferritic matrix, (iii) the Bi + La system exhibited a longer eutectic solidification time and a wider eutectic interval, leading to a lower nodule count, larger average nodule diameter, and reduced nodularity, and (iv) the Bi + Zr-Mn system showed a larger temperature difference between the liquidus temperature and the minimum eutectic temperature, while maintaining an intermediate cooling rate and a higher pearlite fraction. These findings demonstrate that adaptive thermal analysis enables the differentiation of inoculant-dependent solidification behavior and provides a consistent basis for correlating thermal parameters with graphite morphology and matrix constitution in ductile cast irons.

This study investigates the aluminizing kinetics of Hastelloy C276 alloy and evaluates how aluminizing enhances the surface properties of this superalloy. Pack aluminizing was performed on Hastelloy C276 specimens for 2, 4, and 6 h at 600 degrees C, 650 degrees C, and 700 degrees C. SEM observations showed the formation of compact and dense aluminide coatings. According to the XRD analyses, two aluminide phases were indentified (Ni2Al3 and Ni3Al). Ni2Al3 predominates near the coating's outer surface, whereas Ni3Al is concentrated closer to the substrate/coating interface due to lower local aluminum activity. For kinetic studies, the Taylor expansion (TE) model was implemented under a transient diffusion regime to assess the Al diffusion coefficients in the bi-phased aluminized layer. The Al activation energy for Hastelloy C276 was deduced and confronted with the literature results. And the activation energy for Al diffusion in the Hastelloy C-276 alloy was calculated to be 65.26 kJ & centerdot;mol(-1) with the Taylor expansion (TE) model; furthermore, the mass gain per unit associated with the formation of aluminides coating was also evaluated. In the wear experiments performed, it was determined that the application of aluminizing increased the durability of the surfaces and reduced wear losses.

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.

In this study, surface treatments are applied to W350 grade hot work tool steel, including (i) nitrocarburizing and (ii) nitriding, followed by post-oxidation processes, and both tribological performance and wear-related failure of the surfaces against nominal loads (10 and 20 N) at room temperature and 350 °C are evaluated. As a result of nitrocarburizing process, a compound layer ( 8 µm thick) and a diffusion layer ( 120 µm depth) are formed on the surface of the steel having a tempered martensitic structure. By nitriding process, a diffusion depth of 20 µm is reached without forming a compound layer and an oxide film ( 2 µm thick) is coated on this depth with the post-oxidation process. Tribological tests show that (i) material losses due to wear can be reduced due to thermomechanical processes since they provide higher surface hardness compared to the substrate material, (ii) the compound layer can provide higher wear resistance compared to the oxide layer, and (iii) diffusion layer with high load-carrying capacity plays a decisive role in wear performance. Investigations on the worn surfaces indicate that the tendency for abrasive wear can be reduced at room temperature due to the increase in surface hardness by thermochemical processes; however, there is a significant increase in the formation of an adhesive layer on the surface. The resistance of surfaces coated with harder ceramic/oxide components to plastic deformation at higher temperatures has led to a reduction in wear losses.

The optimization of CuNi2Si1 alloy's mechanical and electrical properties was achieved through a combination of experimental approaches and metaheuristic algorithms. Optimizing hardness and electrical conductivity through a variation in aging temperature (450-600 °C) and aging duration (1-420 min) was taken under consideration in the present work. Cold rolling with 50% strain after solution annealing aided in microstructure refinement and accelerated Ni2Si precipitates' development, and property improvement increased. Optimum temperature and holding period were 450 °C and 30 min, respectively, with 266 HV and 13 MS/m and 167 HV and 11.2 MS/m for non-deformed samples, respectively. SPBO, genetic algorithm (GA), and particle swarm optimization (PSO) metaheuristic algorithms were considered, and SPBO exhibited the best prediction accuracy. SPBO predicted 450 °C for 61.75 min, and experimental testing exhibited 267 HV and 14 MS/m, respectively. Polynomial regressions with 0.98 and 0.96 values for R2 confirmed these values' accuracy. According to this work, computational optimization proves effective in optimizing development and property tailoring for application in industries including aerospace and electrical engineering.

By aluminizing at varying temperature (600–700 °C) and time (2–6 h) cycles, defect-free, continuous and homogeneous thick Ni–Al deposition layers are obtained on Hastelloy C276 surface. Metallurgical analysis performed on surface/sub-surface indicates that NiAl 3 and Ni 2 Al 3 phases are the dominant phases within aluminide coatings (11–41 μm). Since the experimental aluminizing process is a diffusion-controlled process, the processing output with variable temperature and time parameters made it possible to study the process kinetics, and the process-specific activation energy is calculated as 51 kJ/mol. An equation is also derived from the regression model to estimate the coating thickness, and there is a good agreement between the coating thicknesses determined by the experimental and calculated values. The effect of temperature/time on the layer thickness is investigated with variance analysis. Although no significant change in the surface hardness value (~ 800 HV) is measured regardless of the layer thickness, an increase in the layer thickness over time on material surface processed at the lowest temperature causes a significant decrease in the oxidation rate due to the presence of a stable Al-rich oxide. All these findings reveal the lowest cost coating conditions that can reduce the chemical degradation of Hastelloy C276 caused by oxidation at high temperatures.

Nickel aluminide (NiAl) alloys produced by spark plasma sintering (SPS) present high potential for hightemperature application due to their superior mechanical and oxidation properties. However, their intrinsic brittleness and susceptibility to wear require treatment of their surface. In this work, the impact of laser-induced remelting (LIR) on the scratch behavior of SPS-processed NiAl alloys under different conditions of processing is studied. The parameters of laser power (30, 50, and 75 W), scanning speed (1000 and 2000 mm/s), and processing atmospheres (air and argon) were modified in sequence to investigate microstructure development and mechanical performance. Thermodynamic simulation of phase stability and solidification paths using ThermoCalc software determined equilibrium phase stability and solidification paths. Scheil simulations proved Al depletion in remelt zones, which modified phase balance of NiAl and Ni3Al. The phase transition was proved using X-ray Diffractometer (XRD), while microstructure refinement and redistributions in elements were identified using scanning electron microscope (SEM) and energy-dispersive X-ray spectrometer (EDS). The scratch tests indicated that LIR significantly enhanced scratch resistance, which reduced wear depth by up to 40 % at loads of 5 N and 15 N. The smooth topography of surfaces upon remelting was proved using 3D profilometry. The findings indicate high potential of using LIR to generate designed NiAl surface properties for application in aerospace and high-performance engineering.

The following study aimed to optimize CO2 laser processing parameters for 1.2379 cold work tool steel to improve its surface properties. As its applications required high durability, strength, and precision, surface roughness and microhardness values were adjusted by varying laser power from 70% to 92%, laser speed from 1 to 5 mm/s, and stand-off distance from 4 to 6 mm. Using these background procedures, this specific study was performed to improve the manufacturing of tool steels used under extreme conditions. Scanning electron microscopy and profilometry were used to identify optimal settings that significantly improved the steel’s surface and subsurface appearances. A speed of 3 mm/s with a power of 81% and a stand-off distance of 5 mm resulted in minimized kerf width, kerf morphology, and spacing and improved uniformity. Using the energy dispersive x-ray spectrum, changes also measured in the distribution of elements, such as the increase in iron and chromium at the surface level of the steel. The effect of the parameters was quantified using analysis of variance (ANOVA) and the Taguchi method, which showed us the proportion of variance that could be described by the amount and specific parameters, with stand-off having the most impact. In this study, the specific effects of certain laser parameters on the microstructural and mechanical properties of cold work tool steel 1.2379 were recorded.

The diffusional powder-pack aluminizing method stands as one of the well-established techniques to enhance the high-temperature oxidation resistance of stainless steels through the formation of Fe-Al coatings. However, it has been observed that the detailed impact of the costly pure Al powder on the characteristics of intermetallic coatings (coating thickness, hardness, fracture toughness, phase structure, grain size, and microstrain) has not been thoroughly investigated, particularly regarding the optimal proportions of Al powder in coating formation. This study is dedicated to the characterization of aluminide coatings formed on AISI 304 stainless steel surfaces using wt.

The current paper deals with the effect of CO2 laser remelting on the surface structuring and oxidation performance of Inconel 718 superalloy, pointing out different laser-induced surface patterns that make a difference in their oxidation properties vital for high-temperature applications. Surface roughness, microstructure, and oxidation behavior characterization were performed using 3D optical profilometry, SEM, and XRD techniques. The oxidation tests conducted at 1000 degrees C for 24 h have revealed that remelted surfaces offered better oxidation resistance compared to untreated samples. Notably, the patterned sample showed the lowest weight gain under oxidation, and a parabolic regime in oxidation occurred after 100 min; while in an untreated reference sample, this appears only after 200 min. This improvement in performance results from the formation of a chromium-rich oxide layer on the melt pools, which acts as an effective barrier against further oxidation. The findings show that laser remelting, especially with grid-like surface patterns, results in an improvement in both durability and high-temperature performance of Inconel 718; therefore, it is apparently a very promising technique for lifespan extension of industrially relevant materials.

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, dissimilar metals HP iron-based nickel alloy and P91 creep resistant steel are welded with gas metal arc welding (GMAW) and microstructural, mechanical and corrosion properties of the joint are characterized. The findings show that (i) depending on the thermal cycle, columnar, cellular and equiaxed dendritic morphologies exist in the final solidification structure of the weld metal and there are Nb and Mo-rich carbides and Laves phases within interdendritic regions, (ii) highest stress concentration is in P91 region and a significant stress accumulates at the austenite grain boundaries of the nickel-based weld metal, (iii) a hardness value of 500 HV1 is reached in the HAZs of the base metals near the surface depending on the secondary phases, but the hardness decreases in the middle and root part of the joint due to the multiple temper effect, (iv) the least toughness is obtained in heat affected zone (HAZ) of HP alloy due to the presence of intermetallics along the grain boundaries and toughness of P91-HAZ is the highest (168 J), (v) fracture varied depending on tensile test temperature and both creep resistance characteristics of filler metal and P91 steel and also dissolution of Laves phase are decisive for the final rupture, (vi) in addition to considerably different corrosion resistance of the base metals, it is observed that the secondary phases in the weld metal reduce the corrosion resistance.

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.

Punching is a cold forming process widely used, especially in the case of mass production. This process can, with optimized parameters, give a high-quality product at low cost. Punch head and shaft failure is investigated while punching S500MC sheet metal. Several techniques such as optical microscopy, Vickers hardness and scanning electron microscopy (SEM) were used in order to get damage causes. The aim of this work is to scrutinize the AISI D2 punch failure and to take out some damage causes. The results show that shaft punch damage is categorized into chipping and wear, however three damage types namely the inflated, the mated and the cracked punch head are found. Back up plate wear, fatigue and high punching force are behind the punch failure.

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.