This study offers a comprehensive understanding of NiCrSiBMoFeCuC coating deposited via HVOF through the use of high-resolution TEM imaging, which provides detailed crystallographic information and defect analysis capabilities. The chemical composition of the coating was evaluated with both SEM-EDS and TEM-EDS, while lattice parameter values were measured using both x-ray diffraction and transmission electron microscopy.

The objective of this study was to quantitatively investigate the build-up of residual stresses in selective laser-melted 316L stainless steel samples and identify the nature of the stresses. In addition, the effectiveness of stress relief heat treatment in reducing residual stresses or changing their characteristics was examined. The results were compared against those obtained from conventionally hot-rolled 316L samples.

In the present study, isothermal oxidation behavior of two multi-layered thermal barrier coatings (MLTBCs) has been investigated. Moreover, the property of the produced coatings were compared with a conventional bilayered TBC. For this purpose, nanostructured and micro YSZ were used as ceramic powder feedstocks and TBCs were deposited by air plasma spray (APS) procedure.

In this work, we investigated the potential of a dense oxide layer in resisting ammonia corrosion. First, the degradation behavior of Hastelloy X substrate and HVOF sprayed CoNiCrAlY coating (as-sprayed condition) was studied in an ammonia gas flow environment. The coating was then heat-treated in air to pre-oxidize the surface, enabling the formation of a dense and stable oxide layer. Thereafter, the degradation characteristics of the pre-oxidized coating was investigated under the same environment. The mechanisms of degradation and corrosion resistance of the materials are elucidated.

In this paper, oxidation behavior of three hardmetal coating compositions with different Cr 3 C 2 content deposited on 1.4828 (AISI 309) or 2.4856 (Alloy 625) substrates was investigated. Heat treatment was performed in a tube furnace in a slight air flow (2 l/h) in the temperature range 500-900 °C for 2–32 days.

This study focuses on the deposition and post-processing behavior of commercially pure copper produced using cold spray additive manufacturing (CSAM) with compressed air. By evaluating the microstructural evolution and mechanical performance of as-deposited and heat-treated copper samples, this work aims to provide insights into optimizing CSAM processes for industrial applications.

This work focuses on the processing and deposit by suspension plasma spraying (SPS) of ZrO 2 -based ceramic materials for Thermal Barrier Coatings (TBC's) applications. The system of interest is ZrO 2 -16mol%Y 2 O 3 -16mol%Ta 2 O 5 (16YTZ). This ceramic has been reported to keep a non-transformable tetragonal phase (t'-phase), suitable to overcome the thermodynamic limits of the mostly used conventional 7-8wt.% yttria stabilized zirconia (YSZ). The research consists into evaluate the t'-phase stability and performance of the 16YTZ SPS coating. Synthesis of 16YTZ and, the evolution of the resulting microstructure in the dense ceramic and in the coating are a central part of the study. Sintering behavior in dense ceramics prepared from both precursor derived and milled powders is evaluated. Microstructural characterization by XRD, SEM and RAMAN spectroscopy of the as-deposited ceramic coating is presented and discussed.

In biomass boilers, corrosion is a prevalent concern that arises at high temperatures. This is mainly because the fuels consumed in these boilers have a high alkali, chlorine, and other molten salt content that has occasionally led to material depletion, leaks, and unforeseen plant shutdowns. Applying protective coatings using thermal spray techniques is a practical answer to this issue. The current work focused on applying powders of Inconel 625 and Inconel 718 to boiler steel using a high-velocity oxy-fuel spraying method. The samples after coating deposition were subjected to the conditions of a biomass-fired boiler for 15 cycles to study the performance of the coatings in a real environment. The decrease of thickness over time was used to evaluate the erosion-corrosion process. Various characterization techniques were used to examine the as-sprayed and eroded-corroded specimens. The X-ray diffraction (XRD) technique was utilized to analyze the phases, while the surface characteristics of powders, coatings, and samples exposed to erosion-corrosion were investigated through scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). When exposed to the actual boiler environment, the findings showed that Inconel 625-coated steel performed better than Inconel 718-coated steel.

The method of simulating the wear performance under working conditions using a high-temperature ultra-high-speed wear testing machine was adopted to study the effect of feed rate variation on the wear behavior and scraping performance of the AlSi/hBN sealing coating and TC4 simulated blades. The macro and micro morphology of the coating and blades were analyzed by stereomicroscope and scanning electron microscope (SEM). The phase composition of the coating was analyzed by energy dispersive spectrometer (EDS) and X-ray diffraction. The results showed that, under the conditions of temperature of 450°C, line velocity of 300m/s, and feed depth of 500μm, the change in feed rate significantly affected the macro and micro morphology and wear mechanism of the AlSi/hBN sealing coating-TC4 simulated blades. At low feed rates, severe wear occurred, mainly manifested as grooving, adhesion transfer, and overheating mechanisms. At medium to high feed rates, good machinability was observed, mainly manifested as cutting and transfer of coating material to the blades.

The need for effective electrical insulation coupled with good thermal conductivity in power electronics has led to an exploration of suitable solutions for components like Insulated-Gate Bipolar Transistors (IGBTs). Considering its material properties, AlN emerges as a promising candidate for this application due to its high thermal conductivity, good electrical insulation and ample dielectric strength. However, aluminium nitride (AlN) has a low deposition efficiency when applied by atmospheric plasma spraying (APS). In contrast to AlN, alumina has a very good deposition efficiency during thermal spraying. Feedstock development was conducted to enhance the coating deposition for AlN. Therefore, a parameter study was carried out with AlN feedstock material to form a protective alumina shell around the AlN particles. Subsequently, the heat-treated powder was applied on an aluminium substrate by APS. X-ray diffraction (XRD) analysis displayed that, the heat-treated feedstock material contained AlN and α-Al 2 O 3 phases. It was observed from scanning electron microscopy (SEM) analysis that the AlN particles formed an oxide shell which led to an enhanced deposition efficiency with a high amount of AlN in the coating. The coatings were also investigated by XRD and SEM to prove the presence of AlN and alumina. For the first time, oxide shelled AlN was successfully applied by thermal spraying with sufficient coating deposition and enhanced AlN-content in the coating.

Cavitation is a wear process in engineering systems caused by the energy release of collapsing bubbles leading to the failure of critical components such as valves, pumps, and propellers. Thermally sprayed coatings can be applied to improve the wear resistance of these components. This investigation considers a WC-NiCrBSi coating composition under cavitation wear, where the WC phase provides the strength and the NiCrBSi matrix offers corrosion resistance in seawater. Coatings were deposited on AISI 440C stainless steel discs of 32mm diameter and 8mm thickness using industrially optimized parameters for the HVOF JP5000 system. Indirect cavitation tests were conducted using a modified ASTM G32 testing procedure on coated test coupons in as-sprayed and Hot Isostatic Pressed (HIPed) conditions. Two tests were performed for each coating using natural seawater of pH 8.19 at room temperature, and averaged wear values are reported to compare the cavitation rate and cumulative mass loss of the coatings. Coating microstructural phases in the as-sprayed and HIPed conditions were identified using X-ray diffraction. The microstructure of the coating substrate system and post-cavitation test wear scars were investigated using Scanning Electron Microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). This investigation provides an understanding of the corrosive-cavitation wear behavior and failure modes of coatings. The cavitation erosion rate and cumulative mass loss results showed that the as-sprayed WC-NiCrBSi coatings improve the cavitation wear resistance of the substrate.

Aerosol deposition (AD) is a novel method for producing dense nanocrystalline ceramic films at room temperature. Previous studies primarily used flat substrates with varying hardness and roughness. However, the development of micro-device applications is increasing the demand for deposition on structured/patterned surfaces. To investigate the impact of substrate patterns on coating microstructure and growth mechanisms in AD, alumina coatings were deposited on patterned Si substrates. Si wafers with patterns of micropillars were employed. The coatings were characterized using laser scanning microscopy, scanning electron microscopy, and x-ray diffraction. The microstructure and density of coatings in the valleys were influenced by the size of and the spacing between the patterns. The results revealed that coatings initially formed in the valleys before covering the entire pattern. Fragments of the initial powder particles became trapped between the patterns, adhering to the groove bottoms and pillar sides. Subsequent particle impacts and densification processes transformed these fragments, ultimately filling the gaps between the walls. With further deposition, a uniform coating surface was achieved.

Due to their promising photocatalytic properties under visible light irradiation, thermally sprayed ZnO-TiO 2 coatings are of interest as substitute for TiO 2 for various industrial applications, like hydrogen production via water splitting or the reduction of organic pollutants in water. Suspension spraying is an effective method to produce coatings in the binary ZnO-TiO 2 system to form Zn 2 TiO 4 in-situ during the spraying process. Aqueous suspensions containing fine dispersed ZnO and TiO 2 particles are mixed at tailored composition and sprayed using the SHVOF and SPS spraying processes. Coatings with homogeneous distribution of elements and different surface structures and phase compositions are obtained. The phase composition is analyzed via XRD. UV-Vis spectroscopy measurements and photocatalytic tests of Rhodamin B degradation are performed. The potential to use appropriate binary suspension feedstock to produce ZnO-TiO 2 -Zn 2 TiO 4 coatings with different microstructures and photocatalytic properties is presented.

Bond coats are used to protect the superalloy from oxidation and to serve as a bond between the ceramic thermal barrier coating (TBC) layer and the superalloy. During high temperature exposures, a thermally grown oxide (TGO) layer forms between the bond coat and the topcoat due to oxygen diffusion, leading to coating failure in the components. This study aimed to investigate the microstructure evolution of three TBCs with different cold-sprayed bond coat alloys after undergoing isothermal heat treatments. The TBCs were heat treated at 1100 °C for durations of 12, 25, and 50 hours to observe the effects of temperature on the microstructure and phase distribution. The microstructure of heat-treated bond coat alloys was examined using scanning electron microscopy and x-ray diffraction. The findings are discussed in relation to the characteristics of the coating alloy and the application process.

Recently, laser deposition technologies have made significant advancements in their ability to manufacture high temperature metals and ceramics. One of these technologies, known as Direct Energy Deposition (DED), has the potential to deposit a wide range of materials from polymers to refractory materials, ceramics and functionally graded materials. This study evaluates major microstructural characteristics of WC-Co additively manufactured by DED technology. This material is commonly used for deposition of protective coatings due to its high hardness and excellent wear resistance. To this end, hardness and wear resistance of the DED processed samples were also investigated in this study. WC-Co coatings are generally deposited using various thermal spray technologies. However, it is speculated that DED deposited WC-Co could provide superior properties such as higher hardness and wear resistance. A DED manufactured WC-Co sample was examined by Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD). Those studies could provide information about important microstructural features, chemical compositions and phase distribution. All the tests were also repeated on High-Velocity Oxygen Fuel (HVOF) deposited WC-Co with the same composition. Both DED and HVOF produced WC-Co coatings experience decomposition of the carbides into compound phases; however, the DED deposited sample displays unique dendritic and eutectic structures that improve the hardness and wear properties compared to the homogenous HVOF coating. In addition, DED produced samples show higher hardness and relatively better wear resistance compared to the HVOF deposited ones. The obtained results could establish a relationship between microstructural characteristics with hardness and wear properties of both samples.

To achieve higher engine combustion efficiency while reducing emissions, it is necessary to address the challenges posed by elevated operating temperatures. High Entropy Alloys (HEAs) have emerged as promising materials for this purpose, offering exceptional properties at high temperatures, including synergistic effects and excellent resistance to oxidation and corrosion. In this study, a FeCoNiCrAl HEA was investigated as a bond coat material due to its excellent balance of strength and ductility, coupled with outstanding oxidation resistance. It was deposited using HVAF M3 and i7 guns equipped with different nozzles/powder injectors and pressures. Notably, this research marks the first study of the i7 gun globally for the HEA bond coat, coupled with the optimization of HVAF parameters for both i7 and M3 guns. Characterization of both powder and as-sprayed samples was carried out using X-ray Diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), and Field Emission Scanning Electron Microscopy (FESEM) techniques. The results revealed the formation of a dense and homogeneous microstructure. Additionally, isothermal oxidation tests were conducted to analyze the behavior of the thermally grown oxide. After 50 hours at 1000 °C, a dense, uniform, and thin alumina TGO layer was observed to have formed. These tests revealed that FeCoNiCrAl HEA exhibits significant potential to enhance oxidation resistance at high temperatures.

The development of materials and alloys for coatings has been increasingly important for reducing costs in different manufacturing processes. The Inconel alloy is widely used due to its chemical inertness and high resistance to high temperatures, but it does not present adequate resistance to erosive wear. In this context, the resistance to wear from cavitation erosion and slurry erosion was evaluated of samples with depositions obtained by laser cladding (Laser directed energy deposition - L-DED) of Inconel 718 and Inconel 718+10%NiNb. The cavitation erosion wear tests were carried out following the ASTM G32 standard (2016), and the ASTM G73-10 standard (2017) was used to evaluate the resistance to slurry erosion wear. The scanning electron microscopy technique (SEM-EDS), and X-ray diffraction (XRD) were used to characterize the cross-section and the surface after wear. The wear mechanism was checked and identified. Microhardness profiles of the cladding cross-section were carried out. The mass loss and wear rate due to cavitation and slurry jet erosion of Inconel 718 and Inconel 718+ 10% NiNb coatings were determined. It was proven that the addition of 10% NiNb in the formation of the cladding caused a 45% increase in average microhardness in the cross-section of the Inconel 718 cladding. The addition of 10% NiNb to the Inconel 718 cladding caused a decrease in mass loss due to slurry erosion from 38.9 mg to 21.9 mg (33%) when the erodent impact angle was 60°.

The multi-layered thermal barrier coatings (TBC) are commonly used in the systems exposed to extensive heat, such as jet engines or gas turbines. The testing of coatings' performance is usually carried out using electric or gas furnace. Concentrated solar power (CSP) could provide cost-effective and environmentally friendly alternative using natural energy source. Moreover, it can also simulate materials exposure in real applications, e.g., in solar power-plants. In this study, possibility of using concentrated solar power to test the performance of hybrid YSZ-based TBCs prepared by hybrid water/argon-stabilized plasma (WSP-H) technology was studied for the first time. In service, TBC top-coat layer may be exposed also to so-called CMAS air-borne particles occurring in the atmosphere which may melt at elevated temperatures and penetrate the coating microstructure, inducing crystallographic and volumetric changes therein. Therefore, testing with the presence of CMAS particles was also included in this study to observe its influence on the coating microstructure under solar irradiation. Changes of the coating microstructures were studied using SEM analysis and X-ray diffraction.

The performance of two distinct coating materials under alumina particle impingement was tested in this study. CrMnFeCoNi and WC-Ni coatings were applied to 2205 duplex stainless steel substrates using cold spray method with nitrogen as the process gas. In between the substrate and the high entropy alloy coating, an interlayer coating of 316 stainless steel was used. The presence of WC particles in the WC-Ni composite coatings was confirmed by SEM cross sectional inspection. Following deposition, the coatings were heat treated in an air furnace. The influence of heat treatment holding time on the WC-Ni coatings was studied using chemical analysis by X-ray diffraction. Heat treatments peak temperatures for the WC/Ni- Ni and high entropy alloy coatings were 600°C and 550°C, respectively. Coatings microhardness and porosity volume fraction were measured for all the samples. The HEA coating outperformed the WC/Ni-Ni hardness but exhibited a higher level of porosity. The coatings were then subjected to erosion experiments using alumina particles with variable impact angles (30°, 60°, and 90°). To compare the different materials, an average erosion value was calculated for each target specimen. The WC/Ni-Ni as-sprayed coating was the most effective against a 60° impingement angle. The HEA coating, on the other hand, demonstrated greater resistance to impact angles of 30° and 90°. SEM was utilized to examine the eroded areas and determine the main mechanisms of erosion.

Cold spraying (CS) of high strength materials, e.g., Inconel 625 is still challenging due to the limited material deformability and thus high critical velocities. Further fine tuning and optimization of cold spray process parameters is required, to reach higher particle impact velocities as well as temperatures, while avoiding nozzle clogging. Only then, sufficiently high amounts of well-bonded particle-substrate and particle-particle interfaces can be achieved, assuring high cohesive strength and minimum amounts of porosities. In this study, Inconel 625 powder was cold sprayed on carbon steel substrates using N 2 as propellant gas under different refined spray parameter sets and powder sizes for a systematic evaluation. Coating microstructure, porosity, electrical conductivity, hardness, cohesive strength and residual stress were characterized in as-sprayed condition. Increasing the process gas temperature or pressure leads to low coating porosity of less than 1 % and higher electrical conductivity. The as-sprayed coatings show microstructures with highly deformed particles and well bonded internal boundaries. X-ray diffraction reveals that powder and deposits are present as γ- solid-solution phase without any precipitations. By work hardening and peening effects, the deposits show high microhardness and compressive residual stresses. With close to bulk material properties, the optimized deposits should fulfill criteria for industrial applications.