Physical Vapor Deposition Method Research Articles

Tailoring biodegration rate of AZ31 magnesium alloy

The biocorrosion phenomenon is an important mechanism that determines the biodegradability capacity. The effectiveness of studies on biodegradable materials is directly proportional to detailed corrosion experiments and analysis of formation mechanisms. In this context, experiments and analyzes have also become frequently used for magnesium alloys. In this study, TiN-based coatings were applied by physical vapor deposition method to tailor AZ31 alloy suitable for use as temporary implant material. Different in vitro media were used for comprehensive simulation of the biological environment, and material losses were interpreted on the basis of corrosive damage.

Surface Engineering of Woodworking Tools, a Review

The wide range of applications of wood are due to its strength properties. The mechanical properties of wood in various parts or directions are different. The complex structure of wood and its hygroscopicity prevent the use of coolants and lubricants, resulting in rapid tool wear disproportionate to the hardness of the processed material. This significantly affects machining efficiency and the quality of the processed surface. It seems that an effective method of reducing tool wear is its modification with a thin hard coating produced by the Physical Vapor Deposition or Chemical Vapor Deposition methods. The article presents tool materials used for woodworking, areas for improving the efficiency of their work, and the impact of thin hard coatings on the increase in tool durability, including binary coatings and also doping with various elements and multilayer coatings. Scientific centers dealing with the above-mentioned subject are also mentioned. A brief review of the effects of surface modifications of woodworking tools in the context of their durability is presented. It was found that the most promising coatings on tools for woodworking were multilayer coatings, especially based on chromium. Higher wear resistance was demonstrated by coatings with a lower coefficient of friction. This value was more important than hardness in predicting the service life of the coated tool.

Thermogravimetric study of 316L steel coated by physical deposit in vapor deposition phase (PVD)

Catastrophic carburization (metal dusting) is one of the problems with the greatest impact on the petrochemical and direct iron reduction industry. This work shows the synthesis of chromium oxide (Cr2O3) coatings on 316L steel as a protective layer to prevent and/or delay material degradation. In this work, the Physical Vapor Deposition (PVD) method will be used, since it is a technique that allows the control of the atmosphere in which the deposition is being carried out, forming high quality thin films, with excellent adherence to the substrate, thus improving its surface properties. Thin films with thicknesses less than one micrometer were obtained, which were subjected to corrosion tests by thermogravimetry in an atmosphere of CH4 at 800°C for 15 minutes and 20 hours, scanning electron microscopy and elemental quantification. The coatings obtained showed an improvement in their resistance to corrosion in critical atmospheric conditions according to the graphs obtained in the thermogravimetry test, observing a lower weight gain compared to the uncoated sample.

(Digital Presentation) Preparation of Metal Halide Perovskite Thin Films Via Laser Deposition

We have been preparing metal halide perovskite (hereinafter referred to as perovskite) thin films by laser deposition. In this study, we report the results of our investigation of the effects of laser wavelength and fluence on the deposition process. One of the most important features of perovskites, which have been rapidly developed in recent years as materials for high-efficiency and low-cost thin-film solar cells, is the applicability of a simple process using solution coating under atmospheric pressure [1]. Crystal growth of perovskite by the solution method occurs through equilibrium chemical reactions, enabling the formation of thin films on the order of μm thickness in less than a few seconds; however, it is difficult to systematically control the crystal growth process at the molecular layer level by the solution method. On the other hand, in the physical vapor deposition (PVD) method, although the deposition rate is relatively low, ranging from sub-nanometer to several nm/s, the deposition can be controlled at the molecular layer level, as well as allowing different atoms to be readily introduced into the film. Therefore, the PVD method allows the addition of elements that are difficult to achieve with solution reactions and is suitable for studies that investigate the effects of such elements on physical properties.In laser deposition (LD), one of the PVD methods, materials are irradiated with an infrared (IR) or an ultraviolet (UV) laser beam, and thin films are formed by evaporation through IR heating or ablation with plasma formation through UV electron excitation. The advantage of LD is that it can cause instantaneous heating or ablation by switching on and off laser irradiation only on the material surface, thus enabling the deposition of molecular layers of organic materials with high vapor pressure or high melting point materials such as inorganic oxides with minimal cross-contamination caused by evaporation. We have prepared perovskite thin films by alternate deposition of PbI2 and CH3NH3I (MAI) using an IR laser and solid-phase reaction at room temperature aiming at the detailed investigation of the crystal growth process and introduction of various dopants in perovskite materials. [2, 3]. In this study, we have also performed perovskite film deposition by UV pulsed laser and investigated the difference in the physical properties of the perovskite films compared to those deposited by IR laser.Fig. 1 shows a schematic structure and appearance of the laser deposition system used in this experiment. The experimental method is described below. A synthetic quartz substrate was introduced into an ultra-high vacuum chamber with a base vacuum of 2×10-5 Pa., Then a semiconductor continuous IR laser (wavelength: 808 nm) or a UV pulse laser beam generated by the fourth harmonic of an Nd:YAG Q-Switch laser (wavelength: 266 nm, 10 Hz) was irradiated alternately onto PbI2 and MAI targets to form CH3NH3PbI3.The optical band gap of the thin films deposited by continuous infrared laser deposition shows a change in optical band gap depending on the thickness of the alternately deposited PbI2 and MAI, which can be attributed to the different content ratios of the tetragonal and orthorhombic phases. Interestingly, in UV pulsed laser deposition, the deposition rate was about 0.35 nm/s under the high laser fluence condition with lens focusing, while a high deposition rate of 20 nm/s was obtained under the low laser fluence condition without lens focusing. This result suggests that the excess kinetic energy of the deposition precursor in the case of lens-focused deposition causes re-sputtering on the surface of the already deposited film, resulting in a reduction of the effective deposition rate.In the presentation, we will demonstrate and discuss the results of crystallinity and optical absorption properties.[1] T. Miyasaka, A. Kulkarni, G. M. Kim, S. Öz and A. K. Jena, Adv. Energy Mater. 2020, 11902500 (2020).[2] K. Kawashima, Y. Okamoto, O. Annayev, N. Toyokura, R. Takahashi, M. Lippmaa, K. Itaka, Y. Suzuki, N. Matsuki and H. Koinuma, Science and Technology of Advanced Materials 18, 307 (2017).[3] N. Matsuki, Y. Iida, T. Shimada, Yuta Abeand T. Sato, ECS Meeting abst. MA2020-02, 1860 (2020). Figure 1

A comparison of tribological and corrosion behavior of PVD-deposited CrN/CrAlN and CrCN/CrAlCN nanostructured coatings

The present study evaluates the tribological and corrosion behavior of CrN/CrAlN and CrCN/CrAlCN nanostructured coatings applied on 430 stainless steel. These coatings were applied using the physical vapor deposition method from the vapor phase through the cathodic arc technique. X-ray diffraction, field emission scanning electron microscopy, and nano-indentation techniques were utilized for the coatings characterization. Moreover, the adhesion of the coatings to the substrate was evaluated by the adhesion test according to the VDI3198 standard. The corrosion behavior of the coatings was studied by potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 wt % NaCl solution in 24, 72, and 168 h. It was observed that CrN was the major phase in the coatings. The results of the Rockwell C test indicated the good adhesion of both coatings to the substrate. The hardness of CrCN/CrAlCN coating was 20 GPa and CrN/CrAlN coating was 18 GPa. Concerning the friction coefficient, 430 stainless steel, CrN/CrAlN, and CrCN/CrAlCN coatings showed friction coefficients of 1.049, 0.3, and 0.21, respectively. CrCN/CrAlCN exhibited the lowest friction coefficient, which can be ascribed to the higher ratio of H3/E2, higher hardness, and also reduced surface roughness compared to the CrN/CrAlN sample. The Rp value of CrCN/CrAlCN coating is higher than that of CrN/CrAlN coating at different times. The corrosion current density of the CrCN/CrAlCN coating was 0.003 μA cm−2 and for the CrN/CrAlN coating, it was 0.057. The obtained results from both corrosion tests are in an agreement and indicate the better resistance of the CrCN/CrAlCN coating against corrosion which can be due to the dense structure, lower roughness, and low wettability of this coating.

Dry reforming of methane over Ni/ZrO2 and NiCu/ZrO2 thin layer nanocatalysts in a microchannel reactor: The effect of coating time

AbstractIn this study, the performance of thin film Ni/ZrO2 and NiCu/ZrO2 catalysts in a microchannel reactor in the dry methane reforming reaction (DRM) is investigated. Thin film nanocatalysts are prepared by the physical vapor deposition (PVD) method. GIXRD, FESEM‐Cross, FESEM‐Surface, and EDX analyzes are used to evaluate the properties of thin film nanostructures. The results show that in addition to the addition of copper as a promoter, a change in the coating time causes a change in the formation of the thin layer and the growth mechanism of the layers. Reactor tests are evaluated at temperatures ranging from 700°C to 800°C, at P = 1 atm, with a CH4:CO2 ratio of 1. Results of this study are compared with two other studies in fixed bed reactors that show the microchannel reactor has better performance. The presence of copper on Ni/ZrO2 could have significant effects on the stability of hydrogen production and the reduction of carbon deposition. Thin film Ni/ZrO2 catalyst with 2 min coating time and NiCu/ZrO2 catalyst with NiCu weight ratio of 4: 1 with 1 min coating time at 800°C show the best performance in terms of hydrogen production and H2/CO ratio (1.43 for a sample of Ni/ZrO2 and 1.68 for a sample of NiCu/ZrO2).

Fractal-like Hierarchical CuO Nano/Microstructures for Large-Surface-to-Volume-Ratio Dip Catalysts

Dip catalysts are attracting interest in both academia and industry for catalyzing important chemical reactions. These provide excellent stability, better recoverability, recyclability, and easy scale-up. Using the unique microstructures of leaf skeletons, we present a fractal-like hierarchical surface that can be used as a versatile and efficient dip catalyst. Copper oxide microcactuses with nanoscalar features were fabricated onto the Bauhinia racemosa leaf skeletons via a combination of physical vapor deposition, electroplating, and chemical oxidation methods. The coated leaf skeletons have a very high surface area, and the three-dimensional (3D) morphology allows the reactants to encounter the catalytic sites efficiently and move around the reaction mixture swiftly. The fabricated bioinspired leaf skeleton-based dip catalyst was characterized and demonstrated to be very efficient for alcohol dehydrogenation reaction, examined under different experimental conditions. A ceramic 3D-printed catalyst holder was designed to hold the catalysts to avoid any damage caused by the magnetic bars during the reactions. The performance is determined using the reaction yields, and the efficiencies are correlated with microcactus-like structures composed of CuO and the 3D fractal-like shape provided by the leaf skeleton. This strategy can be applied to fabricate other dip catalysts using different materials and designs, suitable for catalyzing numerous other chemical reactions.

Failure Mechanism of EB-PVD Thermal Barrier Coatings under the Synergistic Effect of Thermal Shock and CMAS Corrosion

Thermal barrier coatings (TBCs) suffer from the thermo-chemo-mechanical coupling action of thermal shock and calcium–magnesium–alumina–silicate (CMAS) corrosion. However, the failure mechanism of TBCs under the synergistic effect of thermal shock and CMAS corrosion is still unclear due to a lack of an environmental simulator. Herein, an 8YSZ ceramic coating is deposited on a PtAl bond coating/DD419 nickel-based single crystal superalloy substrate using the electron beam physical vapor deposition (EB-PVD) method. The thermo-chemo-mechanical coupling effect of TBCs is achieved in a self-developed environmental simulator. The interaction of volume expansion induced by the phase transition of ZrO2, structural degradation and thermal fatigue further increases the out-of-plane tensile stress and in-plane shear stress in the ceramic coating, which accelerates the initiation and propagation of surface vertical cracks and horizontal cracks. As multiple surface vertical cracks propagate to the interface and merge with interfacial cracks, the ceramic coating spalls from the substrate.

Corrosion Behavior of MoSi<sub>2</sub> Coated Hastelloy X Utilized in Iodine -Sulfur Cycle for Hydrogen Production Application

Molybdenum di silicide (MoSi2) has lower mismatch of coefficient of thermal expansion (CTE) with Hastelloy X as compare to silicon carbide. So, MoSi2 coatings can be a potential candidate to protect Hastelloy X against high temperature sulfuric acid. Herein, MoSi2 thin films were deposited via electron beam physical vapor deposition (EBPVD) method. Corrosion behavior of MoSi2 coated HX and bare HX was analyzed. Corrosion tests of bare Hastelloy X and coated samples was performed at different temperatures (60°C and 120°C) in 98% sulfuric acid using the weight-loss method. The morphology of pre and post corrosion test was also analyzed by using optical microscopy. Bare Hastelloy X showed a slight weight gain at 60°C and a weight loss at 120°C. The MoSi2 coated Hastelloy X showed slight weight gain at 60°C and a weight loss at 120 °C. The weight gain is the result of oxides formation whereas, weight loss may be attributed to corrosion due to H+ ions. These findings were also accompanied by optical microscopy as corroded and very rough patches were evident for bare HX, whereas, for MoSi2 coated samples, the coating was still intact.

Sb2S3/Sb2Se3 heterojunction for high-performance photodetection and hydrogen production

Photoelectrochemical (PEC)-type devices provide promising ways for harvesting solar energy and converting it to electric and chemical energy with a low-cost and simple manufacturing process. However, the high light absorption, fast carrier separation, and low carrier recombination are still great challenges in reaching high performance for PEC devices. As emergent two-dimensional (2D) materials, Sb2Se3 and Sb2S3 exhibit desirable photoelectric properties due to the narrow bandgap, large optical absorption, and high carrier mobility. Herein, Sb2S3/Sb2Se3 heterojunction is synthesized by a two-step physical vapor deposition method. The type-II Sb2S3/Sb2Se3 heterojunction displays excellentphotoelectric properties such as a high photocurrent density (Iph ∼ 162 µA cm−2), a high photoresponsivity (Rph ∼ 3700 µA W−1), and a fast time response speed (rising time ∼ 2 ms and falling time ∼ 4.5 ms) even in harsh environment (H2SO4 electrolyte). Especially, the Sb2S3/Sb2Se3 shows an excellent self-powered photoresponse (Iph ∼ 40 µA cm−2, Rph ∼ 850 µA W−1). This increment is attributed to the improvement in light absorption, charge separation, and charge transfer efficiency. Taking these advantages, the Sb2S3/Sb2Se3 heterojunction also exhibits higher PEC water splitting synergically, which is approximately 3 times larger than that of Sb2Se3 and Sb2S3. These results pave the way for high-performance PEC devices by integrating 2D narrow bandgap semiconductors.

SnS Nanoflakes/Graphene Hybrid: Towards Broadband Spectral Response and Fast Photoresponse.

High responsivity has been recently achieved in a graphene-based hybrid photogating mechanism photodetector using two-dimensional (2D) semiconductor nanosheets or quantum dots (QDs) sensitizers. However, there is a major challenge of obtaining photodetectors of fast photoresponse time and broad spectral photoresponse at room temperature due to the high trap density generated at the interface of nanostructure/graphene or the large band gap of QDs. The van der Waals interfacial coupling in small bandgap 2D/graphene heterostructures has enabled broadband photodetection. However, most of the photocarriers in the hybrid structure originate from the photoconductive effect, and it is still a challenge to achieve fast photodetection. Here, we directly grow SnS nanoflakes on graphene by the physical vapor deposition (PVD) method, which can avoid contamination between SnS absorbing layer and graphene and also ensures the high quality and low trap density of SnS. The results demonstrate the extended broad-spectrum photoresponse of the photodetector over a wide spectral range from 375 nm to 1550 nm. The broadband photodetecting mechanisms based on a photogating effect induced by the transferring of photo-induced carrier and photo-hot carrier are discussed in detail. More interestingly, the device also exhibits a large photoresponsivity of 41.3 AW−1 and a fast response time of around 19 ms at 1550 nm. This study reveals strategies for broadband response and sensitive photodetectors with SnS nanoflakes/graphene.

Thin-Film Coating Methods: A Successful Marriage of High-Quality and Cost-Effectiveness—A Brief Exploration

In this review, several cost-effective thin-film coating methods, which include dip-coating, spin-coating, spray-coating, blade-coating, and roll-coating, are presented. Each method has its own set of advantages and disadvantages depending on the proposed application. Not all of them are appropriate for large-scale production due to their certain limitations. That is why the coating method should be selected based on the type and size of the substrate, including the thickness and surface roughness of the required thin films. The sol–gel method offers several benefits, such as simplicity in fabrication, excellent film uniformity, the capacity to cover surfaces of any size and over vast areas, and a low processing temperature. Nevertheless, these coating methods are somewhat economical and well managed in low-budget laboratories. Moreover, these methods offer thin films with good homogeneity and low-surface roughness. Furthermore, some other thin-film deposition methods, for instance, physical vapor deposition (PVD) and chemical vapor deposition (CVD), are also discussed. Since CVD is not restricted to line-of-sight deposition, a characteristic shared by sputtering, evaporation, and other PVD methods, many manufacturing methods favor it. However, these techniques require sophisticated equipment and cleanroom facilities. We aim to provide the pros and cons of thin-film coating methods and let the readers decide the suitable coating technique for their specific application.

Flame coatings by CCVD (Pyrosil) for R2R applications

Flame coatings by CCVD (Pyrosil) for R2R applications

Characterization of physical vapor deposited coating on acrylonitrile‐butadiene‐styrene and polycarbonate substrates

AbstractIn this study, acrylonitrile‐butadiene‐styrene and polycarbonate substrates plastics were coated with aluminum by physical vapor deposition method in order to determine which one is a better choice for outdoor reflector technology. This investigation has been done by applying the coating on a reflector that is already been used in the lighting industry. Scraping test, caustic soda and caustic potash test, reflection efficiency performance test and surface roughness test methods were used to determine the selection. Coatings on acrylonitrile‐butadiene‐styrene and polycarbonate plastic materials were characterized by scanning electron microscopy and energy dispersive x‐ray spectrometry. Although acrylonitrile‐butadiene‐styrene plastic material is easier for injection molding and cheaper than polycarbonate material, the results showed that polycarbonate plastic material is more efficient than acrylonitrile‐butadiene‐styrene plastic material, especially in terms of surface roughness and reflection efficiency.

Effects of TiN/CrN, CrAlN, and TiN Coatings on the Performance of AISI M2 Tool Steel

The aim of this study is to investigate the effects of various ceramic-based coatings on the performance of AISI M2 high-speed steel punch used in the nut piercing process. AISI M2 punches were coated with TiN, TiN/CrN, and CrAlN utilizing a physical vapour deposition method. The total stroke number of the punches was used to evaluate the tool life of TiN, CrAlN, and TiN/CrN coated AISI M2 punches. AISI M2 punch coated with TiN/CrN was able to work up to greater stroke numbers than punches coated with TiN and CrAlN. Hardness and wear tests were performed to study the wear resistance of TiN/CrN and CrAlN coatings under relatively normal load conditions compared to actual working conditions (impact loading conditions) in the piercing process. The hardness and wear resistance of the CrAlN coating were greater than those of the TiN/CrN coating. The wear performance of the CrAlN coating was higher at normal loads and sliding speeds while the tool life of the TiN/CrN-coated punch was better under impact loading conditions.

Tunning the Activity of Silver Alloy Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

A bottleneck to achieve efficient and stable electrocatalysts for Anion Exchange Membrane Fuel Cells (AEMFCs) is the relatively slow kinetics of the oxygen reduction reaction (ORR) taking place at the cathode. The rather mild alkaline conditions in the AEMFC enable the utilization of various PGM-free catalysts, which brings up new possibilities of finding abundant and inexpensive electrocatalysts without compromising the power density. From theory and previous experiments, it is known that Au and Ag bind oxygen weakly, whereas other transition metals (e.g., Pd, Cu, Fe, Ni) bind strongly to oxygenated species1. Therefore, a suitable geometric arrangement between Ag, an abundant metal with relatively high specific activity, and other metals may give rise to optimum binding of oxygen and thus a high activity. A good strategy to improve the activity of Ag-based catalysts could be a rational design of alloys that can enhance the intrinsic activity of Ag by both ensemble and electronic effects2–4. The former is based on the combination of active sites that facilitate the initial oxygen binding together with Ag active sites that help desorb hydroxide anions, whereas the latter is induced by the alloying metal (which binds oxygenated species strongly) on the electronic structure of the overlaying Ag that tunes its binding to oxygen5. Herein, we report the fabrication and characterization of Ag thin-films alloyed with Pd, Ni, Cu and Mo as a tool to investigate the ORR reaction in terms of ensemble and electronic effects and thus relate alloy composition and geometric arrangement with ORR activity. Ag thin-film model catalysts are fabricated by means of physical vapor deposition methods (PVD) with high control over the amount of material deposited. By varying alloy composition and evaluating electrochemical activity and stability, together with detailed physical characterization, the degree and extent of electronic effects are elucidated. In the same way, sputtering of the same amount of Ag on thin-films of different metals evidences the role of the alloying metal on tuning the activity of Ag through an adjustment of its d-band that changes the binding of oxygenated species, as well as through an ensemble effect that provides active sites for the first elementary steps of the reaction. These results provide insights for more tailored design of electrocatalysts in alkaline media by shedding new light on the mechanisms through which the ORR kinetics are improved in alkaline media. Nørskov, J. K. et al. Origin of the overpotential for oxygen reduction at a fuel-cell cathode. J. Phys. Chem. B 108, 17886–17892 (2004).Betancourt, L. E. et al. Enhancing ORR Performance of Bimetallic PdAg Electrocatalysts by Designing Interactions between Pd and Ag. ACS Appl. Energy Mater. 3, 2342–2349 (2020).Slanac, D. A., Hardin, W. G., Johnston, K. P. & Stevenson, K. J. Atomic ensemble and electronic effects in Ag-rich AgPd nanoalloy catalysts for oxygen reduction in alkaline media. J. Am. Chem. Soc. 134, 9812–9819 (2012).Zamora Zeledón, J. A. et al. Tuning the electronic structure of Ag-Pd alloys to enhance performance for alkaline oxygen reduction. Nat. Commun. 12, 1–9 (2021).Stamenkovic, V. et al. Changing the Activity of Electrocatalysts for Oxygen Reduction by Tuning the Surface Electronic Structure. Angew. Chemie 118, 2963–2967 (2006).

A Path to Significant Reduction of the Interfacial Contact Resistance of Sintered Titanium Porous Transport Layers in Advanced Proton Exchange Membrane Water Electrolyzers

Proton exchange membrane water electrolyzers (PEMWEs) are a leading industry solution to large scale production of green hydrogen, and as a form of energy storage [5]. The PEMWEs have the advantages of having greater energy efficiency, higher product purity, and are environmentally friendly. Within the construction of a PEMWE stack, there are many catalysts coated membranes (CCMs) sandwiched between anode porous transport layers (PTLs) and cathode Gas Diffusion Layers. The PTL is constructed of sintered titanium powder or fibers. The Ti-PTL is on the anode side of a PEMWE cell where the water diffuses towards the CCM. The anode half-cell reaction or oxygen evolution reaction (OER) occurs on this side of the cell. This is important as the PTL is in contact with the bipolar plate (BPP) and the anode catalyst layer [9].A key aspect plaguing the PEMWEs is the highly oxidative and corrosive environment that is typically observed on the anode side. This significantly affects the interfacial contact resistance (ICR) of the components as the corrosion can cause the ohmic resistance of the PTL to increase. In order to combat the corrosion in the PTLs, in this work we use two thin film deposition methods, Physical Vapor Deposition (PVD) and Vacuum Sputtering, to deposit protective metal layers on top of the state-of-the-art Ti PTLs [2]. The explored metal coatings of interest are Platinum (Pt) and Gold (Au) [9]. For the purposes of these experiments, Au and Pt coatings with various thicknesses are deposited on Ti-PTLs by using either PVD or vacuum spattering method. As deposited thin films are characterized by scanning electron microscopy (SEM), digital optical microscopy, and inductively coupled plasma (ICP) analysis. Also, the in-plane conductivity and the ICR of all samples of interest are measured before and after the electrochemical tests by using the 4-probe method and in-house build setup for ICR measurements. The optimal deposition parameters for fabrication of thin, continuous and smooth Pt and Au protective coatings that result in minimum ICR and improved in-plane conductivity of the PTLs of interest are identified, and the results will be reported at the ECS 241 meeting.

A Review of Coating Methods and Their Applications in Compression and Spark-Ignition Engines for Enhanced Performance

Coating of metallic surfaces such as cylinder heads, cylinder liners, piston heads and exhaust-valves in Internal Combustion Engines (ICEs) has improved engine performance in areas of brake-thermal-efficiency including brake-specific-fuel consumption, etc. This review showed different methods of coating in compression and spark-ignition engines for improved performance using different coating thicknesses on the metallic surfaces. These coating thicknesses may be either minimum or maximum depending on the coating method used. The coating methods discussed in this paper were Thermal Spraying (TS), Physical-Vapour Deposition (PVD), Chemical-Vapour Deposition (CVD) and Ion Implantation methods. Minimum thicknesses were achieved using the PVD, CVD and Ion-Implantation methods. In addition, Sol-Gel and Slurry coatings were also discussed. Having considered these methods of coating, thermal-spraying method was recommended for compression and spark-ignition engines because it produces temperature ranging from 8000 K-14000 K on surfaces with thick coating thicknesses.

Improving the mechanical, tribological, and electrochemical behavior of AISI 304 stainless steel by applying CrN single layer and Cr/CrN multilayer coatings

The purpose of this study was to assess the mechanical and tribological behavior of chromium nitride (CrN) single layer and multilayer nanostructured coatings of chromium/chromium nitride (Cr/CrN) applied on AISI 304 stainless steel to be used in a marine application. CrN and Cr/CrN coatings were performed using cathode arc evaporation a division of physical vapor deposition (CAE-PVD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM) were utilized for phase identification of coatings and surface morphology, respectively. Nano-indentation method was used to investigate the mechanical behavior of coatings. The tribological behavior of the coatings was studied by the ball-on-disk method. The results indicate that the mechanical behavior of the Cr/CrN multilayer nanostructured coatings is better in comparison to the CrN single-layer coatings. The hardness values of CrN and Cr/CrN coatings were 21.5 and 23.3 GPa, respectively. The higher hardness of the nanolayered coating might be owing to blocking the movement of dislocations and microcracks by its layered structure. Furthermore, the tribological behavior of AISI 304 stainless steel was highly amended by applying the coatings. The coefficient of friction for CrN and Cr/CrN coatings in a dry condition decreased from 0.61 to 0.49 and 0.46, respectively. Also, the CoF value reduced from 0.57 to 0.38 and 0.37 in 3.5 wt% NaCl electrolyte. The lower friction coefficient of the Cr/CrN multilayer nanostructured coating is perhaps due to its higher hardness and lower roughness.

Metal-ceramic diffusion barrier nanocomposite coatings on nickel based superalloys for corrosion and high temperature oxidation resistance

Ceramic diffusion barrier coatings are inevitable in high temperature aerospace and nuclear applications to protect superalloys from oxidation and hot corrosion. Compositionally graded coating (CGC) of Ni-YSZ with five layers was deposited on an Inconel-690 substrate through electron beam physical vapor deposition (EBPVD) method. After heat treatment, the phase formation and crystallite determination in each layer of the CGC were studied by X-ray diffraction. Pulsed radio frequency glow discharge optical emission spectroscopy (RF-GDOES) showed outward diffusion of Ni towards the surface of the CGC. High resolution transmission electron microscopy (HRTEM) studies of the cross-sectional region of the heat-treated coating at 1273 K revealed no secondary phases within the coating as well as at substrate-coating interface. The corrosion behavior of Ni-YSZ coating under 3 M HNO3 medium showed that the heat-treated CGC of Ni-YSZ exhibited better corrosion resistance due to the formation of NiO than as-deposited Ni-YSZ coating.