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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.

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.

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.