Intensive R&D work of more than one decade has demonstrated many unique coating properties, particularly for oxide ceramic coatings fabricated by suspension thermal spraying technology. Suspension spraying allows producing yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC) with columnar microstructure, similar to those produced by electron-beam physical vapor deposition (EB-PVD), and vertically cracked morphologies, with a generally low thermal conductivity. Therefore, suspension sprayed YSZ TBCs are seen as an alternative to EB-PVD coatings and those produced by conventional air plasma spray (APS) processes. Nonetheless, the microstructure of the YSZ topcoat is strongly influenced by the properties of the metallic bondcoat. In this work, direct laser interference patterning (DLIP) was applied to texture the surface topography of Ni-alloy based plasma sprayed bondcoat. Suspension plasma spraying (SPS) was applied to produce YSZ coatings on top of as-sprayed and laser-patterned bondcoat. The samples were characterized in terms of microstructure, phase composition and thermal cycling performance. The influence of the bondcoat topography on the properties of suspension sprayed YSZ coatings is presented and discussed.

Cold spray process was chosen as a good candidate for dimensional restoration and protection of components. Commercially pure aluminum, aluminum-alloy or titanium were recommended for different applications. This paper investigates laser surface texturing association to enhance durability of sprayed coatings. Laser is easy automated, localized and reliable process. It was applied for prior-surface treatment. Textured surfaces were produced and compared to conventional treatments, such as grit-blasting, in terms of deposition efficiency and adhesion bond strength. Patterns promoted direct particle embedment. Particle-substrate interface exhibited significant temperature rate and strain in cavities. Intimate contacts and particle compressive states were assumed responsible for improvement. The particle deformation and bonding behaviors were evaluated and discussed for the different configurations. Thus, window of deposition was increased with laser surface texturing. Anchoring mechanisms increased two fold the adhesion strength compared to conventional pre-treatments. In one case, the interface was stronger than the coating cohesive strength.

The aim of this work is to better understand the build-up of thermal barrier coatings (TBC) on microtextured substrates, particularly the influence of geometry on the behavior of plasma jets in substrate boundary layers. Coatings produced by suspension plasma spraying served as an experimental reference for numerical analysis, which involved advanced turbulent flow and volumetric heat source modeling along with the use of commercial fluid flow software. Geometric and numerical models were used to simulate the generation of plasma inside the torch and the resulting plasma flow with its highly nonlinear thermophysical characteristics. This work opens the possibility of predicting feedstock particle movement and deposition, which is essential in understanding coating build-up mechanisms in general and the flow of fine particles on substrate surfaces in particular.

In this work, binder-free Co 3 O 4 films with in-situ oxygen vacancies are deposited in a one-step process by solution precursor plasma spraying (SPPS). It is believed to the first time Co 3 O 4 layers composed of hexagonal flakes were synthesized through the SPPS route. Specific capacitances up to 1700 F/g were obtained at a scan rate of 5 mV/sec, almost 97% of which was retained after 13,000 cycles at 20 mV/sec. This supercapacitor-like performance is attributed to the synergistic effects of a binder-free composition with in-situ oxygen vacancies and porous nanostructures.

This study assesses the durability of superhydrophobic surfaces that possess a scalable architecture similar in morphology to branching or corymbose coral. In the experiments, electrolytic copper powders with a coral-like morphology are cold sprayed onto metal, ceramic, and glass substrates, forming a textured copper layer with a structural hierarchy based on the morphology of the powder. After cold spraying, a flame treatment is applied, creating a porous layer of Cu 2 O over the pliable Cu surface, which further increases roughness. As a final step, a fluoroalkyl silane spray is applied to reduce surface energy. It is shown that the fluorinated surface retains its excellent water repellency after cyclic bending and folding, sand-grit erosion, knife-scratching, and even heavy loading with simulated acid rain. It also retains its adhesion to glass (17 MPa), ceramic (12 MPa), and metal (34 MPa) substrates.

In this study, aluminum coatings were cold sprayed, with and without laser assistance, on laser-textured aluminum 6060 and Fe52 steel substrates. The results indicate that laser texturing makes for a cleaner coating interface than grit blasting and that the benefits are greatest when spraying on harder substrate materials. For the steel substrate, the optimized topography achieved through laser texturing assisted in particle deformation, leading to the formation of a much tighter coating structure. Laser-assisted cold spraying, in turn, improved deposition efficiency as well as coating density and adhesion. Separately or together, the two processes have proven to be beneficial for cold spraying.

In this study, NiCr alloy coatings were deposited by arc spraying using different combinations and mixtures of pressurizing gases and other process modifications. Coating properties were examined mainly by SEM, EDS, and conductivity measurements. The results show significantly reduced oxygen contents and improved coating morphologies compared to reference coatings produced using current plasma processes. Improved microstructure is shown to have a positive effect on surface quality and specific resistivity, making it possible to texture arc-sprayed coatings just as successfully as the plasma-sprayed reference layers. Moreover, the temperature coefficients and resistivities of arc-sprayed NiCr were found to be superior to those of conventionally manufactured coatings.

This paper investigates a hypothesis for understanding how the substrate texture influences the adhesive strength. A surface-scale fractal analysis is carried out on measured surface textures obtained from various metallic substrate materials. The results of these area-scale analyzes are correlated with the adhesive tensile strength of the finished coating. The results show that scale-considering fractal parameters predict bond strength better than average roughness, and that they support a hypothesis that relates bond to available surface area at a given scale. Paper includes a German-language abstract.

During grinding of thermally sprayed WC-Co, the grinding ratio G ( ratio of volume of work removed to the volume of wheel consumed) is usually low and the finish produced sometimes is inadequate. Improvement in surface finish accompanies increase in grinding ratio. The objective of this investigation is to study the effect of type of abrasive, table speed, and depth of cut on the surface finish and hardness of WC-Co. Thermally sprayed WC-12 wt % Co and WC-17 wt % Co produced using the high velocity oxygen fuel (HVOF) process, have been ground using silicon carbide and diamond wheels under different operating conditions. The surface profile reveals the significant role played by the above parameters on the surface finish. The grinding ratio, G in case of diamond grinding was found to be larger than silicon carbide grinding however, the quality of the surface finish produced by silicon carbide was better than the diamond. The surface structure of the ground WC-Co was examined by SEM. Surfaces ground using a silicon carbide wheel exhibited extensive plastic flow, while surfaces ground with diamond wheels are highly fractured with localized flow which suggests two different mechanisms of material removal. The surface hardness after grinding, was found to depend on the type of abrasive and table speed. Silicon carbide grinding has shown higher hardness and better surface finish than diamond grinding.