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Background:In the past few years, Magnetite (Fe3O4) nanoparticles have gained a significant research interest in the field of biology, chemistry, metallurgy due to their wide range of applications. Some of their important applications include drug delivery, chemotherapy, low-friction seals, magnetic fluid, adsorbent, recovery of hazardous wastes, etc.Methods:In the present paper, we reported an eco-friendly route of preparing magnetite nanoparticles by using leaves of Tilia Tomentosa (Ihlamur) followed by calcination at 400 ˚C for 15 minutes.Results:The bandgap energy of the prepared Fe3O4nanoparticles was studied by UV–Visible spectroscopy and the value was found to be 3.31 eV. The scanning electron microscopy (SEM) image showed the spherical magnetite nanoparticles with an average size of 25 nm. The phases and thermal properties of Fe3O4nanoparticles were studied by using X-ray diffraction, thermogravimetric (TG) and differential thermal analysis (DTA). The enthalpy change of Fe3O4nanoparticles was calculated by using the DTA curve and the value was found to be 4.97 kJ/mol at 8˚C/min heating rate. The antimicrobial activity of Fe3O4nanoparticles was carried out by the minimum inhibition concentration (MIC) assay method. Except for B. subtilis, Fe3O4nanoparticles demonstrated significant antibacterial property.Conclusion:The prepared magnetite nanoparticles showed excellent thermal stability and less weight loss over a 30–1000 ˚C temperature range. The size of the prepared magnetite nanoparticles is very less therefore they interacted effectively with the organelle, enzymes, and cells of bacteria and inhibited bacterial growth by killing them.

We have successfully studied the charge transfer kinetics between carbon paste electrodes and dopamine using green synthesized rectangular monoclinic CuO nanoparticles (NPs) prepared by Alchemilla vulgaris leaves with the one-pot green synthesis method. The scanning electron microscopy (SEM) results confirmed the monoclinic structure with a particle size of around 85 nm. The investigation of thermal properties was carried out by thermogravimetric (TG) and differential thermal analysis (DTA). We also studied the electrochemical response of green synthesized CuO nanoparticles to detect Dopamine (DA) using cyclic voltammetry, which was proven to be an excellent electrocatalyst for the electro-oxidation of DA. The fabricated CuO nanoparticle modified carbon paste electrode (CMCPE) depicts fantastic selectivity, robustness, and sensitivity in analyzing DA in clinical and pharmaceutical preparations. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) orbitals of the DA were studied using positive and negative charges at the CuO modified carbon paste electrode interface. Frontier molecular orbitals of DA are plotted to understand electron transfer reactivity at the electrode interface.

The ZnO nanoparticles (NPs) are considered to be one of the inexpensive and very important bioactive materials widely used in drug delivery, as a photo-catalyst material, antibacterial, bioimaging, anticancer, anti-inflammation, wound healing, and diabetes treatment. Therefore, we have prepared ZnO NPs using Alchemilla vulgaris (Lady’s mantle) leaves and investigated their anti-enzymatic properties. Phases of the ZnO NPs were determined from X-Ray diffraction (XRD) spectra. The shape and size of the green synthesized NPs were investigated by scanning electron microscopy (SEM) and it confirms the cauliflower shape with an average size of 120 nm. But the beads inside the cauliflower shape are 20 nm in size. The prepared ZnO NPs show the cumulative median particle size of 550 nm. The thermogravimetric (TG) and differential thermal analysis (DTA) were performed at different heating rates to study the percentage of weight loss, and activation energy. The activation energy was calculated to be 4.98 kJ/moles using Kissinger method. We also studied the enzyme inhibition effect of ZnO NPs containing biologically active groups on important metabolic enzymes like butyrylcholinesterase(BChE), acetylcholinesterase (AChE) and α-glycosidase (α-Gly) enzymes. The bandgap of ZnO NPs was also studied by UV–Vis spectroscopy via Tauc's method and it was determined to be 3.27 eV. The photocatalytic property of the ZnO NPs was executed against rhodamine B (RhB) under the illumination of an AM 1.5 solar simulator.

Hot corrosion and oxidation cause very destructive damage in thermal barrier coatings (TBCs) during service conditions. In hot corrosion, TBCs exposed to molten salts lose their integrity easily due to the phase transformations while oxygen easily penetrates from the TBCs to bond coats and forms thermally grown oxide (TGO) layer which causes higher stresses at the interface of bond and top coating. In the current study, CoNiCrAlY powders were sprayed by high-velocity oxygen fuel (HVOF) technique on Inconel 718, and then yttria-stabilized zirconia (YSZ) and YSZ/Gd2Zr2O7 ingots were deposited by electron beam physical vapor deposition (EB-PVD) technique on the bond coated substrates. Isothermal oxidation tests were carried out at 1000 degrees C for 8, 24, 50, and 100 h, while hot corrosion tests were carried out at 1000 degrees C in the presence of NaCl, Na2SO4, and V2O5 molten salts with 5, 10, 15, and 20 h cycles. The produced coatings, as well as the oxidation and hot corrosion test results, were examined using SEM, EDS, XRD, and image analysis techniques. After the tests, the Gd2Zr2O7 layer was found to exhibit superior oxidation and hot corrosion performance as compared to the conventional YSZ TBC system.

Inconel 718 has a wide area of applications in gas turbines, aircraft, turbocharger rotor equipment, and so many other applications, including applications with temperatures up to ~700 °C. In this study, Ni-based aluminide coating on Inconel 718 alloy was applied by pack cementation technique. Phase structures, layer coating thickness, hardness, wear, and oxidation behaviors were studied for different aluminization temperatures and times (600 and 700 °C for 3 and 5 h). The change in the layer from the surface to the inside was varied from 8 to 80 μm and this was increased with higher aluminization temperature and more time. The hardness value of 960 HV was determined in the coating layer whereas the hardness of the matrix was 260 ± 10 HV. The wear resistance of the samples was tested under dry sliding conditions with different loads. The wear resistance of Inconel 718 has increased with aluminization. Increased aluminization duration and temperature reduced wear losses. Isothermal oxidation test results at 1000 °C for 5, 25, and 125 h show that Inconel 718 has a poor oxidation resistance under these conditions while aluminized Inconel 718 samples exhibit better results. The comparison of the aluminized Inconel 718 samples after oxidation tests showed that the aluminization at higher temperatures allowed the formation of a compact and continuous alumina layer while the formation of porosities under the oxide scale weakened the adherence and durability in the others.

Thermal barrier coatings (TBCs) commonly expose to oxidation, hot corrosion, and CaO-MgO-Al2O3-SiO2 (CMAS) attacks during the service condition. All of these attacks cause the spallation or delamination of TBCs from the bond coat. In this study, the effect of these attacks on YSZ and La2Zr2O7/YSZ TBC systems was investigated. YSZ and double layer La2Zr2O7/YSZ topcoats were deposited using electron beam physical technique (EB-PVD) on CoNiCrAlY bond coat produced by cold gas dynamic spray (CGDS) technique. CMAS tests at 1225 degrees C for 4, 8, 12, 16, 20, 24, 28, and 32 h and 5 h cyclic hot corrosion tests at 1000 degrees C were carried out on TBCs. Before and after the tests, TBCs were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), x-ray diffraction (XRD) and image analysis software program. At the end of the tests, the formed phases, microstructural changes, and general failure mechanisms were investigated in detail for each test. The general result shows that double-layered TBCs provide significant contributions and durability against high-temperature corrosive attacks of conventional YSZ TBC. In addition, in this study, hot corrosion damage mechanism and CMAS attack significantly damaged the column morphology of the EB-PVD method, reducing the thermal insulation properties and strain tolerance of TBCs. As a result of the tests, spallation and phase changes occurred in the damaged TBC systems.

Thermal Barrier Coatings (TBCs) are generally used in both industrial gas turbines and aircraft engines. In this study, metal powders with CoNiCrAlY content were coated on Inconel 718 nickel-based superalloy substrate materials using the cold gas dynamic spray (CGDS) method, which is a new generation thermal spray coating method. As a top coating, YSZ and Gd2Zr2O7/YSZ (GZO/YSZ), respectively, single and double layer ceramic layers were deposited with an innovative method, physical vapor deposition by electron beam (EB-PVD). All produced TBC systems were sprinkled with vermiculite powder containing CMAS minerals and subjected to CMAS corrosion tests and the effect of CMAS damage on the phase stability and microstructure of TBC systems was determined using elemental mapping analysis, X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM). According to the results obtained, it has been determined that the double layer TBC system with GZO/YSZ is more resistant to CMAS damage than the single layer YSZ system.

Ever-increasing energy costs and environmental restrictions have compelled researchers to focus on the reutilization of vast amounts of industrial by-products such as blast furnace slag and steelmaking slag, in energy extensive and material extensive industries such as iron-steel production and construction. Attempts to reutilize these waste materials all around the world have yielded successful results up to date, such that, in some of these attempts they even surpassed their intended use as blend or replacement materials and became serious rivals to their industrial counterparts. Various ways to reutilize these waste materials have been explored up to date, including waste heat recovery, clinker substitute in cement production, and a number of comparatively more value added applications. The ongoing attempts have come to a point that pushes the limits for more technological uses such as alternative ceramic coating materials in surface engineering applications. In this regard, this review study aims to provide an overview of and a collective approach to various uses of blast furnace and steelmaking slag in diverse applications and fields, with a view to provide insight into the current attempts to optimize or improve their use, as well as emerging trends as to the potential use of these waste materials in higher value-added applications.

In recent years, carbon fiber-reinforced polymer (CFRP) composites materials are frequently used in many areas such as aerospace, military, automotive, construction, marine vehicles, wind turbines, motorcycles, bicycles, sport, electrical and household appliances due to superior properties of this material such as high specific strength, high stiffness and high corrosion resistance. While the parts produced with this material are durable and lightweight, the increase in CFRP composite material usage requires the development of processing methods with low cost and high quality. The surface quality in milling of CFRP composite materials is an important issue due to the influence of surface quality of the produced parts on the assemblage. It has also importance on the fatigue resistance of the machined parts. On the other hand, CFRP composite material is seen as one of the hard-to-cut materials due to its low thermal conductivity and abrasive nature. Rapid tool wear occurring during the milling process deteriorates the surface quality, leads to the decline in production due to the machine tool downtime and it thereby causes a cost increase accordingly. Therefore, diamond tools are widely used in machining of CFRP composite material due to their high hardness, while these tools are expensive. In order to overcome the tool cost issue, cemented carbide tools are used to cut CFRP composite material. Although carbide tools have higher toughness than diamond ones, their hardness is low. Therefore, they are commonly protected by a hard coating to increase their surface hardness and wear resistance. However, the tool life and cutting performance of the carbide tools in machining of CFRP material need to be improved. In this study, after investigation the studies on milling process of CFRP composite materials in the current literature, the emerging developments were presented. Cutting tool geometry and materials used in the relevant area are compiled. Tool wear mechanisms that occur during the milling process, the failures in CFRP composite material and the solutions to prevent these failures are discussed.

Reduction of machining times and optimization of cutting parameters and conditions hold great importance in machining processes. Milling is among the most important machining processes used for machining of fiber-reinforced composite materials. The present research was carried out to investigate the effect of cutting parameters on tool wear during the milling of carbon fiber reinforced polymer (CFRP) materials which are widely used in aviation and aerospace industries. A multidirectional CFRP composite material with 6 mm width and 24 layers was used as the workpiece. The tests were performed under dry conditions on a CNC vertical processing center with 100, 200 and 300 m/min cutting speeds; 0.05 – 0.15 and 0.25 mm/tooth feedrates and at 1 mm constant cutting width. To understand the wear process, scanning electron microscopy (SEM) analyses of the worn surfaces were performed.

Thermal Barrier Coatings (TBCs) provide thermal insulation for gas turbine components operating at high temperatures. Generally, TBCs were produced on a MCrAlY bond coat with 7-8% Yttria Stabilized Zirconia (YSZ) using Atmospheric Plasma Spray (APS) technique. In this study, Inconel 718 substrate material was coated with CoNiCrAlY bond coat using high velocity oxygen fuel (HVOF) technique. Afterward, Gd2Zr2O7 was deposited on samples using Electron Beam Physical Vapor Deposition (EB-PVD) technique. Produced TBCs were exposed to isothermal oxidation tests at 1000°C for 8 h, 24 h, 50 h and 100 h in muffle furnace. Scanning electron microscopy-energy distribution X-ray (SEM-EDX) spectroscopy was used to investigate thermally grown oxide (TGO) layer and TGO growth behavior of TBCs. In addition, X-ray Diffractometer (XRD) analysis was performed to TBCs to understand whether phase transformation occurs or not before and after oxidation.

Thermal barrier coatings (TBCs) are mostly used in critical components of aircraft gas turbine engines. Hot corrosion is among the main deteriorating factors in TBCs which results from the effect of molten salt on the coating–gas interface. This type of corrosion is observed as a result of contamination accumulated during combustion processes. Fuels used in aviation industry generally contain impurities such as vanadium oxide (V 2 O 5 ) and sodium sulfate (Na 2 SO 4 ). These impurities damage turbines’ inlet at elevated temperatures because of chemical reaction. Yttria stabilized zirconia (YSZ) is a conventional top coating material for TBCs while Gd 2 Zr 2 O 7 is a new promising top coating material for TBCs. In this study, CoNiCrAlY metallic bond coat was deposited on Inconel 718 nickel based superalloy substrate material with a thickness about 100 μm using cold gas dynamic spray (CGDS) method. Production of TBCs were done with deposition of YSZ, Gd 2 Zr 2 O 7 , YSZ/Gd 2 Zr 2 O 7 ceramic top coating materials using EB-PVD method, having a total thickness of 300 μm. Hot corrosion behavior of YSZ, Gd 2 Zr 2 O 7 , YSZ/Gd 2 Zr 2 O 7 TBC systems were exposed to 45 wt.% Na 2 SO 4 and 55 wt.% V 2 O 5 molten salt mixtures at 1000 °C temperature. TBC samples were investigated and compared using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis and X-ray diffractometer (XRD). The hot corrosion failure mechanisms of YSZ, Gd 2 Zr 2 O 7 and YSZ/Gd 2 Zr 2 O 7 TBCs in the molten salts were evaluated.

Yttria Stabilized Zirconia (YSZ) is widely used as a traditional ceramic top coat material in gas turbine engine components. Nowadays, rare earth zirconates, as alternative materials to YSZ, are enhanced for use as top coat layer of TBC owing to their better thermal isolation properties. In the present study, metallic CoNiCrAlY bond coat powder was sprayed on Inconel 718 superalloy substrate by cold gas dynamic spray (CGDS) technique. After the deposition of bond coats, YSZ and Gd 2 Zr 2 O 7 top coats were produced using EB-PVD process. TBCs were exposed to isothermal oxidation tests at 1100 °C for 8, 24, 50 and 100 h. Oxidation and growth behaviors of thermally grown oxide (TGO) layer were observed. TBC samples were investigated using scanning electron microscope (SEM), EDS elemental mapping and X-ray diffractometer (XRD) analysis before and after the oxidation tests. Oxidation performances of two different TBC systems were compared to each other according to the analysis results.

12th International Symposium on Applied Plasma Science (ISAPS) -- SEP 24-28, 2019 -- Univ Yamanashi, Yamanashi, JAPAN WOS: 000538148400048 Oxidation is an inevitable failure mechanism under the operating temperature in gas turbines. To avoid negative effects of oxidation, ceramic-based materials having low thermal conductivity and high stability should be used to hot section components. In accordance with this purpose, thermal barrier coatings (TBCs) are used in order to increase the lifetime of gas turbine engine components that have not reached to desired levels yet. Yttria stabilized zirconia (YSZ) has been used as a conventional top coat material in TBCs. Increased the turbine inlet temperatures (TIT) promote to researchers to try higher stable material such as rare earth zirconates. In this study, CoNiCrAlY metallic powders were sprayed using a new emerging technique as called cold gas dynamic spray (CGDS) on Inconel 718 substrates. Single layer YSZ, Gd2Zr2O7 and double-layered YSZ/Gd2Zr2O7 were deposited by electron beam physical vapor deposition (EB-PVD) technique as top coat materials. In high temperature furnace, both TBC samples were isothermally oxidized at 1000 degrees C under different time periods. TBCs were examined as microstructural before and after oxidation tests. Thermally grown oxide (TGO) layer forming at the interface during oxidation were investigated and compared for each TBC systems. Oxidation and TGO growth behaviors were discussed. Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [113R049] This investigation was financially supported by The Scientific and Technological Research Council of Turkey (TUBITAK, 113R049).

MCrAlY coatings are widely preferred in materials used at high temperature applications exposed to oxidation and hot corrosion. The coating process used in the production of thermal spray coatings directly affects the microstructure and lifetime of the coating. In this study, a CoNiCrAlY metallic bond coat was deposited on Inconel 718 superalloy substrate material using APS, SSAPS, D-gun, HVOF and CGDS spraying techniques. The produced coatings were subjected to isothermal oxidation tests at 1000 °C for different exposure times. Porosity, surface roughness, XRD, SEM, EDX-elemental mapping analysis were used to investigate and determine the microstructures and the changes in the dimensions of thermally grown oxide (TGO) layer as a function of time and temperature. The obtained data were compared before and after the oxidation tests, and the findings were evaluated considering other related studies within the literature. The results show that CGDS CoNiCrAlY coatings exhibited better oxidation resistance than the coatings produced by the other techniques.

Technology-oriented applications are becoming more important in today’s world and the use of technological processes continues to grow rapidly, day by day. Because of the advantages offered by composite materials, there is a great deal of interest in this material group in various industrial applications. Composite materials continue to develop at a great pace in parallel with the developments in metallic, ceramic and polymeric materials. Therefore, composite materials have found wide usage in engineering materials in recent years. In this material group, carbon fiber reinforced polymer (CFRP) composite materials, from the advanced composite material class, are commonly preferred in strategic applications due to their outstanding features such as high load-carrying capacity and low density. In this study, the production, characteristics and industrial usages of CFRP composite materials, milling and drilling operations carried out on them are presented along with current technology-oriented applications.

Carbon fiber-reinforced polymers (CFRPs) have very good mechanical properties, such as extremely high tensile strength/weight ratios, tensile modulus/weight ratios, and high strengths. CFRP composites need to be machined with a suitable cutting tool, otherwise, the machining quality may be reduced, and failures often occur. However, as a result of the high hardness and low thermal conductivity of CFRPs, the cutting tools used in the milling process of these materials complete their lifetime in a short cycle, due to especially abrasive wear and related failure mechanisms. As a result of tool wear, some problems, such as delamination, fiber breakage, uncut fiber and thermal damage, emerge in CFRP composite under working conditions. As one of the main failure mechanisms emerging in the milling of CFRPs, delamination is primarily affected by the cutting tool material and geometry, machining parameters, and the dynamic loads arising during the machining process. Dynamic loads can lead to the breakage and/or wear of cutting tools in the milling of difficult-to-machine CFRPs. The present research was carried out to understand the influence of different machining parameters on tool abrasion, and the work piece damage mechanisms during CFRP milling are experimentally investigated. For this purpose, cutting tests were carried out using a (Physical Vapor Deposition) PVD-coated single layer TiAlN and TiN carbide tool, and the abrasion behavior of the coated tool was investigated under dry machining. To understand the wear process, scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) was used. As a result of the experiments, it was determined that the hard and abrasive structure of the carbon fibers caused flank wear on TiAlN- and TiN-coated cutting tools. The best machining parameters in terms of the delamination damage of the CFRP composite were obtained at high cutting speeds and low feed rates. It was found that the higher wear values were observed at the TiAlN-coated tool, at the feed rate of 0.05 mm/tooth.

The cold gas dynamic spray (CGDS) method has been considered a promising technology to produce a metallic bond coat for thermal barrier coating (TBC) systems. In this study, CoNiCrAlY bond coats produced by CGDS method were coated with yttria-stabilized zirconia (YSZ) by electron beam physical vapor deposition (EB-PVD). TBCs were subjected to 50 wt % V2O5 and 50 wt % Na2SO4 molten hot corrosion salt combinations at 1000 &deg, C. In the case of YSZ top coat on TBCs, the reaction between Na2SO4, V2O5, and Y2O3 salts generates YVO4 crystals, and these structures cause the transformation of tetragonal ZrO2 to monoclinic ZrO2. This situation occurs under operating conditions that lead to TBC failure. Hot corrosion behavior and the related failure mechanisms of TBC systems were investigated and discussed using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, and X-ray diffractometer (XRD).

In this study, CoNiCrAlY metallic coatings were deposited on an Inconel 718 Nickel-based superalloy substrate material using the detonation gun (D-gun) and supersonic plasma spraying (SSPS) techniques. The microstructural and mechanical properties in addition to their room and high-temperature wear behavior of the produced coatings were evaluated. The wear tests were performed at room temperature (rt), 250 and 500 &deg, C using 2N and X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) analyses of the worn coatings were performed to assess their wear performance. The coatings produced with D-gun process exhibited higher hardness and lower porosity (550 &plusmn, 50 HV0.25 hardness and 1.2 &plusmn, 1.0% porosity) than SSPS coatings (with 380 &plusmn, 30 HV0.25 hardness and 1.5 &plusmn, 1.0% porosity) which resulted in better room- and high-temperature wear performance for D-Gun coatings. The worn surfaces of both coatings exhibited formation of tribological layers and superficial microstructural changes by varying temperature and load conditions. Increasing load and temperature resulted in increased wear loss whereas increasing temperature resulted in reduced COF values for both coatings.

The present study was carried out to investigate the isothermal oxidation behavior, thermal cyclic performance and oxidation kinetics of thermal barrier coatings (TBCs) systems consisting of CoNiCrAlY metallic bondcoats produced by Atmospheric plasma spraying (APS) and high velocity oxy fuel spraying (HVOF) on Inconel 718 substrate. Yttria stabilized zirconia (YSZ) ceramic top coats was produced by APS process as for the insulation layer. The oxidation behavior of the coatings were investigated under isothermal oxidation conditions at 1000 °C, 1100 °C and 1200 °C for 8, 24, 50 and 100 h. The results of the experimental studies on the oxidation kinetics and microstructural evolution of APS and HVOF sprayed thermal barrier coatings (TBCs) are compared and discussed in the paper. The microstructural changes at the metallic/ceramic interface and growth behavior of the thermally grown oxide (TGO) layers during the isothermal oxidation and thermal cyclic tests were analyzed in detail. © 2018 Elsevier B.V.

Purpose Thermal barrier coatings (TBCs), which are used in high temperature applications of gas turbines, are damaged due to fuels and airborne minerals under working conditions. Stable zirconia coatings, which are usually used as topcoat materials in TBCs, are damaged by interacting at high temperatures with elements such as vanadium and sulfur from low quality fuels. The purpose of this paper is to see the failure mechanism of TBC systems after hot corrosion damages. Design/methodology/approach CoNiCrAlY metallic bond coatings of TBC samples were produced by cold gas dynamic spray method which is a new trend production method and stabilized zirconia ceramic top coating was produced by atmospheric plasma spray method. In total, 50% by weight of V2O5 and 50% Na2SO4 salt mixtures were placed on TBC samples and subjected to hot corrosion test at 1000°C. Findings Hot corrosion behaviors of TBC samples were examined by scanning electron microscopy, elemental mapping analysis, energy dispersive X-ray spectrometry analysis and X-ray diffraction analysis. TBC samples were damaged at the end of 12-h cycles. Originality/value The paper provides to understand the mechanism of hot corrosion of TBCs with cold sprayed metallic bond coat.

As one of the main failure mechanisms emerging in the milling of carbon (C)-fiber-reinforced polymer (CFRP) materials, delamination is primarily affected by cutting tool material and geometry, machining parameters and the dynamic loads arising during the machining process. In this study, machinability tests were performed without the use of coolants to examine the effect of machining parameters on multidirectional CFRP composite workpieces, which have a wide application in industries. The tests were applied on a computer numerically controlled vertical processing center at three different cutting speeds (100, 200 and 300 m/min), three different feed rates (0·05, 0·15 and 0·25 mm/tooth) and constant cutting depth (1 mm). Following the tests, the changes in the workpiece were examined in terms of surface roughness, cutting forces, tool wear and delamination failures. The average surface roughness increased with increasing feed rate. Cutting forces also increased with increasing cutting speed, which caused improvements on average surface roughness values. As a machining parameter, feed rate was found to be a determining factor in the machining of CFRP composite materials.

WOS: 000483627700003, Thermal barrier coatings (TBCs) are commonly applied specifically for aerospace applications in which they are subjected to air-borne particles. Therefore, solid particle erosion behavior of all coating layer has been an important phenomenon and erosion behavior of various TBCs has been widely investigated in literature. In the present study, CoNiCrAlY and yttria stabilized zirconia (ZrO2 + 8% Y2O3) powders were deposited on Inconel 718 nickel based super alloy substrate. Atmospheric plasma spraying technique was applied for the deposition of the metallic bond coat and the ceramic top coats. Erosion tests were carried out under various particle impingement angles with an air jet erosion tester. Afterwards, eroded surfaces of the specimens were investigated with a three-dimensional (3D) optical surface profilometer (noncontact) and scanning electron microscope. The erosion rates, the areal surface roughness values, the 3D surface topographies, and the surface morphology of the specimens were evaluated based on the particle impingement angle to understand the solid particle erosion behavior of the produced coatings. The maximum erosion rates occurred at 60 degrees impingement angle which is an indication of semi-ductile/semi-brittle erosion behavior. Furthermore, the surface roughness values and surface topographies also dramatically varied depending on the impingement angle. Deeper and wider erosion craters formed at 60 degrees impact angle and the erosion craters were visualized by profilometer analysis., Selcuk University Scientific Research ProjectsSelcuk University [15201071], The study was also supported by Selcuk University Scientific Research Projects under the Grant Number of 15201071.

Thermal barrier coatings (TBCs) are widely used to increase gas turbine efficiency and to prolong the lifetimes of superalloy substrates. Yttria (7–8%) stabilized zirconia (YSZ) is used as a state of the art TBC top coating material. In recent years, rare earth zirconates have drawn interest as top coating materials due to their high phase transformation temperature and low thermal conductivity. In the present research, CoNiCrAlY powders were sprayed on Inconel 718 superalloy substrates using high velocity oxy fuel (HVOF) deposition technique. YSZ, Gd2Zr2O7 (GZ) and YSZ/GZ top coats were then deposited on the resulting bond coat using EB-PVD technique. The produced TBCs were exposed to isothermal oxidation at 1100 °C for 4 different periods, and furnace thermal cyclic tests were conducted at 1150 °C. After thermal loadings, TGO (thermally grown oxide) growth behavior and crack surfaces of TBCs were evaluated. Samples were compared with each other using analysis techniques like scanning electron microscopy (SEM), energy dispersive sprectrum (EDS) elemental mapping and X-ray diffraction (XRD) before and after the oxidation tests. The results showed that double layered TBC system is more durable against high temperature degradations.

Hot corrosion is a very destructive failure mechanism for thermal barrier coatings (TBCs) during service conditions. In the present study, a CoNiCrAlY is coated using atmospheric plasma spray (APS) and high velocity oxy-fuel (HVOF) techniques which produces TBCs that were exposed to 50% Na2SO4 and 50% V2O5 molten salts at 1000 °C. The top surface was visually inspected at the end of each four-hour cycle to determine the lifetime of TBCs. The failure criteria required for the termination of the hot corrosion cycles was assumed to be 25% cracking and spallation of top coats. X-Ray Diffraction (XRD) analysis was performed before and after hot corrosion tests in order to observe new phases which may occur in the top coating. After scanning electron microscopy (SEM) images of cross-section samples of hot corrosion tests are completed, samples were taken. As a result, it has been observed that the lifetimes of HVOF bond-coated TBCs are longer.

In this study, severe shot peening (SSP) has been performed to commercially pure titanium (Grade 2) specimens in order to expose severe plastic deformations to the material surface. S230 shot media with higher air pressure conditions have been selected for SSP. A nanocrystalline layer has been created by means of severe plastic deformation. The nanograined structure has been investigated via XRD, FESEM, and microhardness methods. SSP specimens have been subjected to thermal oxidation treatment in air at 500 and 700 °C for 2 and 16 h. Severe shot peened commercially pure titanium has a thicker oxide layer when compared to as received ones. The results show that both SSP and thermal oxidation improve the wear characteristics.

In this study, ferrochromium (FeCr) slag, which is available as an industrial waste, is proposed as a protective surface coating material particularly for protection of continuous casting rolls against oxidation. FeCr slag was successfully deposited with atmospheric plasma spray (APS) method. Before the coating process, FeCr slag powder prepared in the particle size range of 5-38m, was investigated using conventional characterization methods (XRD, SEM, TGA etc.). Thermal Barrier Coating (TBC) system was used as a basis for deposition processes. Accordingly, NiCoCrAlY (Amdry, -45+5m) was firstly deposited as metallic bond coat layer onto the surface of AISI 420 substrate, and then FeCr slag layer was deposited as the top coating layer. After the deposition of FeCr slag powder, the resulting coating layer was found to have low porosity with a homogeneous microstructure. The deposited FeCr slag coatings were subjected to isothermal oxidation tests at different temperatures and test durations for determination of their oxidation behavior and upper operating temperature limits. The results obtained from this study indicate that FeCr slag can be considered as an alternative protective coating material for caster rolls which are subjected to high temperatures up to 800 degrees C.

Thermal barrier coatings (TBCs) are widely used in aerospace and aviation industries for materials required to withstand severe environments such as oxidation, hot-corrosion failure and CMAS (calcia–magnesia–alumina–silica) attack or vermiculite corrosion. This is particularly apparent in vermiculite, which can penetrate sand, volcanic ash and is the most destructive damage mechanism in the TBC system. Impurities from the desert environment such as calcia–magnesia–alumina–silica (CMAS) cause degradation of TBCs. In this research, CoNiCrAlY metallic bond coatings were deposited on Inconel 718 nickel based superalloy substrates with a thickness of around 100 μm using a Cold Gas Dynamic Spray (CGDS) technique. Production of TBCs were carried out with deposition of YSZ ceramic top coating material using Electron Beam Physical Vapor Deposition (EB-PVD), with a thickness of around 200 μm. The effect of CMAS with spreading naturally-occurring mineral (vermiculite) on TBC samples were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) analysis and X-ray diffraction (XRD). The microstructure evolution of YSZ and failure mechanism of TBC were evaluated.

Thermal barrier coatings (TBCs) are extensively used to protect critical components such as aircraft turbines to provide thermal insulation at elevated temperatures. At high operating temperatures, damage mechanisms such as oxidation and hot corrosion result in spallation of TBC system. The spallation occurs due to the phase transformation during penetration of hot corrosion salts to top coat. YSZ is mainly used as top coat material for TBC systems. However, YSZ cannot be used in temperature higher than 1000 °C. More superior efficiency of gas turbine engines will demand a new generation materials for TBC systems. Nowadays, rare earth zirconates, Gd 2 Zr 2 O 7 ,La 2 Zr 2 O 7 , YSZ/Gd 2 Zr 2 O 7 , and YSZ/La 2 Zr 2 O used as ceramic top coat materials in gas turbine engine components owing to their superior thermal isolation and hot corrosion resistance properties. In this study, hot corrosion mechanism, rare earth zirconates, and their properties as well as their hot corrosion behavior in TBCs were investigated based on literature studies. This investigation was financially supported by Scientific Research Projects (BAP) Coordinatorship of Karabuk University with the project code of KBÜBAP-17-DR-259 and the Scientific and Technological Research Council of Turkey with the project code of TUBITAK, 113R049. This study was carried out as a Ph.D. thesis by Yasin Ozgurluk in the Graduate School of Natural and Applied Science at the University of Karabuk, Turkey.

TBCs provide protection of superalloy substrates against harsh environments in gas turbine engines. Typical TBCs consist of two main coating layers called bond and top coat. Recently, zirconates have become attractive top coat materials as an alternative to yttria stabilized zirconia (YSZ) due to their superior thermal properties. Zirconates are deposited on YSZ layer to decrease the thermal conductivity and to minimize the oxygen penetration. Furthermore, their high melting point as well as phase stability and sintering properties render them promising materials for TBC applications. In this regard, YSZ and YSZ/La2Zr2O7 top coats were deposited using EB-PVD technique on HVOF-CoNiCrAlY bond coated Inconel 718 superalloy, in the present research. TBCs were exposed to isothermal oxidation tests in high temperature furnace at 1000 degrees C with different time periods and also, they were subjected to furnace cycling tests at 1150 degrees C. After oxidation and thermal cycling tests, formation of thermally grown oxide (TGO) layers at the interface and crack surfaces were investigated according to analysis results. The results show that double layered TBC system exhibits better oxidation performance in terms of TGO growth and thermal cyclic lifetime compared to single layer TBC system.

Nichrome (NiCr) coatings are widely used to provide resistance against oxidation and corrosion in many machine components. TBCs must include bond coatings that are resistant to oxidation resulting fromhigh-temperature operating conditions. In the present study, NiCr powders were sprayed on nickel-based superalloy Inconel 718 substrates using atmospheric plasma spray (APS) technique. Bond-coated substrates were coated with yittria stabilized zirconia (YSZ). As such, the TBC samples were kept at 1000°C for 8 h, 24 h and 50 h in high temperature furnace and their isothermal oxidation behavior was investigated. Microstructure and phase change properties of TBCs before and after isothermal oxidation were then studied and analyzed.