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Shape memory alloys (SMAs) are increasingly used in the fields of aviation, automotive and biomedicine due to their unique properties. Nickel-Titanium (NiTi) alloy materials, which are one of the shape memory alloys, are among the most frequently used alloy materials. The shape memory and super elastic effects of NiTi alloys, high ductility and deformation hardening make it difficult to shape burr. An additional problem is the formation of a white layer during machining. In this study, surface milling operations were performed in dry cutting conditions with uncoated cutting tools with different nose radii. The processing parameters were determined based on the experience gained as a result of the preliminary tests. Tungsten carbide cutting tools with different nose radii (0.4mm and 0.8mm) were used for the milling operations. Milling was carried out at three different cutting speeds (20, 35, 50 m/min), feed rates (0.03, 0.07, 0.14 mm/tooth), and a constant axial cutting depth (0.7 mm). As a result of our experimental studies, the best tool life was found to be in 0.8 mm nose radius cutting tools at 20 m/min cutting speed and 0.03 mm/tooth feed rate (0.264 mm). The minimum average surface roughness was found after milling with 0.8 mm nose radius cutting tool at 20 m/min cutting speed and 0.03 mm/tooth feed rate (0.346 μm). It has been determined that increasing the cutting tool nose radius reduces both the flank wear over the cutting tool and the average surface roughness.

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.

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.

The aim of this study was to optimize machining parameters to obtain the smallest average surface roughness (Ra) and flank wear (Vb) values as a result of the surface milling of a nickel-titanium (NiTi) shape memory alloy (SMA) with uncoated cutting tools with different nose radius (r&epsilon, ) under dry cutting conditions. Tungsten carbide cutting tools with different r&epsilon, (0.4 mm and 0.8 mm) were used in milling operations. The milling process was performed as lateral/surface cutting at three different cutting speeds (Vc) (20, 35 and 50 m/min), feed rates (fz) (0.03, 0.07 and 0.14 mm/tooth) and a constant axial cutting depth (0.7 mm). The effects of machining parameters in milling experiments were investigated based on the Taguchi L18 (21 &times, 32) orthogonal sequence, and the data obtained were analyzed using the Minitab 17 software. To determine the effects of processing parameters on Ra and Vb, analysis of variance (ANOVA) was used. The analysis results reveal that the dominant factor affecting the Ra is the cutting tool r&epsilon, while the main factor affecting Vb is the fz. Since the predicted values and measured values are very close to each other, it can be said that optimization is correct according to the validation test results.

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.

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.

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.

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.