In this work, cold spray shot peening was used to treat interstitial-free (IF) steel. Different numbers of impact passes were evaluated and the microstructure and hardness evolution in IF steel were analyzed. Based on the experimental results, the potential of CSSP to achieve surface strengthening and properties enhancement in metallic materials is demonstrated.

In this study, suspension plasma spray coatings were fabricated using two different plasma torches, both equipped with a mechanical injector. A parametric study was performed to evaluate the effects of five process parameters on coating porosity: suspension mass load, spray distance, plasma power, spray step, and substrate roughness. A linear regression model of porosity was established. The model has the potential to predict the global porosity in the coating.

Thermal spray coatings are typically applied to grit-blasted, rough surfaces, though coating models generally assume smooth substrates. This research involved simulating nickel coating formation on rough stainless-steel substrates in an atmospheric plasma spray process. The researchers evaluated coating topography, porosity, thickness, and roughness using a Monte-Carlo stochastic algorithm. The temperature differential between coating and substrate creates residual thermal stresses, which were analyzed using NIST's Object Oriented Finite element software (OOF). Results indicate that substrate roughness increases coating roughness and creates non-uniform stress distribution with concentration points at the coating-substrate interface.

This study evaluates the surface protection of a waste-to-energy boiler wall using the Eutronic Arc Spray Gun 4 HFH. The test involved coating a 3.2 m² section of the boiler membrane wall with four materials: BTW 58 (FeCr-based), METCO 8294 (NiCrMo alloy), TAFALOY 71T (Inconel 625), and Metcoloy 4 (FeCr steel). Before spraying, the surface was grit-blasted to SA 3 finish with a roughness of 75–100 μm. Coatings were applied both with and without a Metco 8450 bonding layer. Additionally, two high-temperature ceramic coatings—Fireside and Tubearmor—were tested. The wear tests were conducted on-site in the boiler's third pass. After one year of exposure, samples were evaluated for condition, wear, and scale formation. BTW 58 and TAFALOY 71T, particularly when combined with Fireside ceramic coating, provided the most effective protection.

In this study, the two primary goals were: (i) to investigate the impact of laser ablation parameters on the physio-chemical nature and surface texture of the substrate, and (ii) to identify the optimal laser parameters to maximize the coating's adhesion to the substrate.

The polymer cold spray (CS) process has been demonstrated as a promising coating and repair technique for fiber-reinforced polymer composites (FRPs). However, a noticeable variation in coating thickness (herein referred to as checkerboard pattern) often occurs in the initial (bond) layer of low-pressure CS deposition. The checkerboard pattern occurs due to essentially periodic variations in matrix thickness above the subsurface fiber weave pattern. When the bond layer exhibits the so-called checkerboard pattern, the CS deposition for subsequent layers may be negatively affected in terms of deposition efficiency, porosity, adhesion, surface roughness, and surface thickness consistency. The present work compares results of both numerical simulations and experimental studies performed to reveal the governing mechanisms for and elimination of checker-boarding. Numerical single particle impact simulations are conducted to observe various thermomechanical domains for CS impact on the FRP surface in different regions of the composite material. Complementary experimental CS studies of exemplar powders onto FRPs with various surface interlayer thicknesses are also presented. Experimental analyzes of deposits include microstructural observations to compare against the simulations while also providing practical strategies for the elimination of checkerboarding effects.

Coating adhesion by thermal spraying method requires sufficient surface roughness on particle scale particles impacting the surface, particularly in the case of plasma spraying with particle melting state. Grit blasting process is mainly used to create the fine asperities required for spread particles to adhere. To further increase adhesion, the use of laser texturing for metallic substrates is benefit and is already well documented in literature. In the case of ceramic substrates such as alumina, grit blasting with corundum particles is no longer effective in creating a roughness of a few micrometers. Laser texturing therefore appears to be a potential candidate for generating adhesion in coatings. In this work, adhesion mechanisms of three different coatings produced by Atmospheric Plasma Spraying (APS) on a textured alumina substrate were investigated. The influence of substrate surface texturing by two different laser methods, a pulsed nanosecond laser and a continuous laser, was studied. YSZ was chosen as a potential Thermal Barrier Coating (TBC) and Al 2 O 3 and Y 2 O 3 were selected as bondcoats to observe the variation of adhesion mechanisms on ceramic substrates. Textured patterns and coating microstructures were observed by numerical and electron microscopy. Different adhesion mechanisms occurred depending on coating material. Either the geometrical parameters of the pattern and the surface roughness developed by a nanosecond laser and a continuous laser respectively, can promote mechanical anchoring and thus, a real adhesion.

Surface coatings play a pivotal role in enhancing mechanical and functional properties of various materials. High Entropy Alloy (HEA) annealed coatings have garnered significant interest due to their potential to improve wear resistance and overall durability. This research presents a comprehensive study focused on the characterization of HEA annealed coatings. It focuses on evaluating their roughness and wear performance. In this research, a systematic approach is adopted to assess the effects of annealing on coating surface properties. The investigation begins with the deposition of the Al 0.1-0.5 CoCrCuFeNi and MnCoCrCuFeNi coatings using a well-established cold spray (CS) technique, followed by a controlled annealing process. The coating surface roughness is analyzed using profilometry and microscopy techniques. This offers insights into the changes induced by annealing. The wear performance of the annealed coatings is evaluated through tribological tests.

Thermal Spraying of tungsten carbide is usually performed to optimize surface hardness. However, often there are additional coating or process requirements, e.g., low porosity, low roughness, or high deposition efficiency, that must be met to satisfy the customer or increase the process efficiency. Such optimizations are difficult because various influencing factors, e.g., lambda (λ), standoff-distance, or powder feed rate, have different effects on the individual coating and process properties. In this study, several trials were performed and analyzed (technically & databased) to understand how each influencing factor affects these coating and process properties. It could be determined that there is no general best performance parameter but that only individual solutions depending on prioritized importance of the properties can be obtained. Using data, one way of solving the challenge is the performance of multi-objective optimization. With the help of this method, the challenges of optimization can be solved using test data. The simultaneous optimization can be visualized in a 2D/3D graph. A boundary line can be observed where different process and coating characteristics are optimized. Applying such databased methods can help to work more efficiently as well as more sustainable in development and application.

High-pressure die casting (HPDC) is a well-established manufacturing process used in the automotive sector to make high-precision components. The necessity to reduce fuel consumption increases the use of low-density components in the automotive industry. Corrosion induced by molten metal is one of many failure modes for dies, changing the die's geometry and surface roughness. All combined wear changes the dimensional precision of the manufactured parts but also the surface quality of the components. Many additive deposition methods are applied to decrease wear and recover the surface. Thermally sprayed coatings can improve the surface properties and recover the geometry of the die caused by the aluminum attack. The main objective of this work is to observe the behavior of the H13, Cr3C2-25NiCr, and WC10Co4Cr coatings deposited by HVOF and HVAF, tested against Aluminum corrosion and Die-soldering tests. After dissolution, the chromium carbide reacts with the aluminum, creating a tough intermetallic interface, and raising the extraction tensile stress. After Aluminum corrosion tests, it was observed that the WC 10Co 4Cr HVAF coating presented low adhesion to the aluminum with no observed coating failure due to the formation of intermetallic. Die soldering tests indicated that the WC 10Co 4Cr protects the substrate, resulting in lower extraction tensile stress than H13 base material and other HVOF coatings. It was possible to observe that WC 10Co 4Cr HVAF coating showed results comparable to AlCrN PVD coating.

Carbon fiber (CF) composites are widely used in the aerospace industry due to their light weight and favorable mechanical properties. Nevertheless, applying protective coatings (e.g. erosion resistance) through thermal spraying presents specific challenges with defects such as distortion, oxidation, and poor coating adhesion. This study presents a new technique that combines electroless plating processes and thermal spray for depo-siting metals onto polymer-reinforced composites. Samples of low melting polyaryletherletone (LMPAEK) thermoplastic polymer reinforced with carbon fibers aligned in the normal direction (ZRT film) are plated (with copper, silver, or nickel) to provide an adhesion layer for the thermal spray processes. Subsequently, pure tin and titanium (i.e. Ti-6Al-4V) is deposited on the samples using High Velocity Air-Fuel (HVAF) and atmospheric plasma spray (APS) processes. Cross-sections of the resulting coatings are compared, and the materials are characterized for surface roughness, cracks and pores.

The properties of the coating depend, among other things, on the preparation of the substrate surface and the spray parameters. One of the key properties of the coating is its adhesion to the substrate. Suitable preparation of the substrate surface has a great influence on the adhesion of the thermal spray coating. This work aims to study the influence of surface preparation on roughness of substrate and the resulting surface adhesion of coating. Another aim was to compare the effect of the chosen adhesion measurement method. A series of measurements of the roughness of the samples after grit blasting was performed. The effect of using new and used corundum was also taken into account. The selected coating for testing was TWAS (twin Wire Arc Spray) sprayed Zn15Al. The substrate material was low carbon steel 1.0570. The following adhesion measurement methods were chosen for the experiment - adhesion tensile test according to ASTM C633 - 79 standard, method using a special sample holder based on the ASTM C633 - 79 standard. In addition, a series of measurements were performed using Elcometer 510 Model T.

Thermally sprayed WC/CoCr coatings are the most established coatings in the valve industry. However, due to the high wear resistance and as-sprayed surface roughness, the surface post processing costs are very high. Near-net-shaped fine powder coatings have the possibility to reduce the costs effectively. Due to the high specific surface to volume ratio of the powders, undesired phase transformations can occur during the spraying process. To avoid such phase transformations, the novel thermal spraying process Ultra-HVOF (UHVOF) is used in this study. An extensive parameter study is carried out on the influences of the process parameters on microhardness, porosity, as-sprayed surface roughness, phase composition and wear resistance. With suitable process parameters, near-netshaped and almost pore-free coatings can be applied. Compared to a conventional HVOF sprayed WC/CoCr coating, a wear reduction by a factor of three can be achieved in a pin-on-disktest against Al 2 O 3 at a load of F = 15 N. Due to the pore-free and highly wear-resistant coatings, significantly thinner coatings can be used for the protection against corrosion and wear in valves. In addition, the required surface quality of the near-net-shape coatings can be achieved by polishing only. Thus, the novel UHVOF coatings represent a cost-effective alternative to conventionally used valve coatings.

The enhancement of the surface characteristics and corrosion resistance of cobalt alloys is under continuous examination for its biomedical applications. In this work, the investigation of corrosion performance of cobalt alloy coated with HA and HA/ZnO reinforced powders using plasma spray technique revealed that on the continuous increase of ZnO reinforcement the corrosion resistance improved progressively. The increment in surface hardness and drop in surface roughness was examined with the rise in ZnO content. Each coated sample exhibits a hydrophilic property. According to SEM and EDX investigations, homogeneous distribution of HA/ZnO coatings and intact reinforcement of ZnO in pure HA powder was noticed. All of the coated specimens maintain their morphological integrity, ensuring excellent protection of the prepared samples. The obtained outcomes denote HA/ZnO reinforced coatings on CoCr alloy as a suitable combination of enhanced surface properties and excellent corrosion resistance for future bone implant practices.

As a supersonic solid-state deposition process, Cold Spray (CS) has a unique role among other thermal spray techniques as it uses compressed and heated gas to accelerate particles to a critical velocity. CS can be an expensive process, especially when helium is used as a processing gas. In recent thermal spray developments, High-Velocity Air Fuel (HVAF) has taken a specific place in terms of providing dense and strong coatings similar to CS, but also coatings with less oxidation than High- Velocity Oxy-Fuel (HVOF). In contrast to these techniques, HVAF uses a mixture of fuel and air, instead of pure oxygen as in HVOF, to accelerate particles. Therefore, HVAF appears as a relatively cheaper and environmentally friendly alternative for the deposition of a wide variety of materials. The aim of this research is to produce fully dense copper coatings with limited oxidation using an inner diameter (ID) HVAF system and to compare the microstructure with CS copper coatings. Coating microstructures, surface roughness, and microhardness are studied using different characterization methods such as Scanning Electron Microscopy (SEM). Through this paper, the influence of both spray processes, CS and ID-HVAF, on the deposition of copper coatings is discussed. Cross-sectional studies of different coatings show a fairly dense microstructure for CS and ID-HVAF coatings. Moreover, it is discussed how the copper coating properties can change upon modifying the spray parameters.

This research presents a novel approach for producing metal matrix composite powders using a nanoparticle decoration technique. A 1wt% stable suspension of 30nm Al 2 O 3 particles was decorated onto primary AA6061using a redispersion method. The resulting AA6061-1wt% Al 2 O 3 composite powder was mixed in a rotary mixer for one hour and subsequently dried at 45°C. Scanning electron microscopy of the composite powder confirmed the successful material composition. The composite powders were then deposited onto an AA6061 substrate using a low-pressure cold spray system, with the coating quality, deposition efficiency, surface roughness, and hardness of the deposited materials analyzed. After heat treatment at 430oC, the role of the nanoparticles in hindering recrystallization was studied, with Orowan strengthening shown to be the main mechanism for preventing recrystallization and grain growth. This technique provides a promising alternative method for producing metal matrix composites and offers potential for further exploration of their properties and applications.

Driven by the search for an optimum combination of particle velocity and process temperature to achieve dense hard metal coatings at high deposition efficiencies and powder feed rates, the high velocity air-fuel spraying process (HVAF) was developed. In terms of achievable particle velocities and temperatures, this process can be classified between high velocity oxy-fuel spraying (HVOF) and cold gas spraying (CGS). The particular advantages of HVAF regarding moderate process temperatures, high particle velocities as well as high productivity and efficiency suggest that the application of HVAF should be also investigated for the manufacture of MCrAlY (M = Co and/or Ni) bond coats (BCs) in thermal barrier coating (TBC) systems. In this work, corresponding HVAF spray parameters were developed based on detailed process analyses. Different diagnostics were carried out to characterize the working gas jet and the particles in flight. The coatings were investigated with respect to their microstructure, surface roughness and oxygen content. The spray process was assessed for its effectiveness. Process diagnostics as well as calculations of the gas flow in the jet and the particle acceleration and heating were applied to explain the governing mechanisms on the coating characteristics. The results show that HVAF is a promising alternative manufacturing process.

Thermal barrier coatings have provided a revolution in the industry as they allow a higher operating temperature of equipment, improving the efficiency of gas turbines. However, one of the biggest challenges in terms of increasing the lifespan of TBC systems is the attack of fused silicates or simply CMAS (Calcium-Magnesium-Alumina-Silicate). CMAS are particles from the environment that can penetrate the TBC structure and cause delamination of the coating when exposed to high temperatures during thermal cycling. In this study, a plasma sprayed YSZ coating in the as coated and surface treated condition were given CMAS depositions from various preparation methods, and then subjected to thermal cycles at different evaluation temperatures and exposure times. The permeability of the ceramic layer and the penetration path of CMAS at different temperature levels were evaluated, as well as the penetration characteristics in relation to the microstructure of the ceramic layer. X-Ray diffraction and Scanning Electron Microscopy were used to characterize the applied CMAS and the penetration kinetics and conditions. Samples with longer exposure time had a considerable volume increase. The conditions to guarantee the formation of the silicate and its consequent wettability are also discussed.

High-pressure cold spraying has shown significant potential in manufacturing metallic composite coatings for a wide range of industrial applications, including wear and corrosion protection. Quasi-crystalline materials, in turn, are promising candidates due to their unique microstructural features. Combining these concepts, metallic composite coatings were generated using high-pressure cold spraying to produce functional and protective coatings. Several spray trials were done to detect the effect of compositions and size of quasi-crystalline feedstock materials mixed with metal powders, Al6061, and stainless steel 316L, on coating microstructure, integrity, and surface properties. A scanning electron microscope was used to examine the microstructure of the feedstock materials and composite coatings. A 3D surface optical profilometer was also used to investigate surface texture. The wettability of the coating surfaces was measured by static water contact angles using a droplet shape analyzer. Cold-sprayed quasi-crystalline composite coatings showed denser and well-integrated deposits with a random distribution of phases across the composite surface, indicating promising structural reliability and hydrophobic behavior.

Surface treatments and coatings are widely used to protect components from wear and corrosion. Of all available methods, thermal spraying is arguably the most versatile with regard to coating material and morphology. Surface roughness and porosity can be adjusted in a wide range depending on the requirements. However, as-sprayed coating surfaces inevitably exhibit a certain roughness necessitating post-treatment if a smooth surface is required. The surface roughness of thermal spray coatings is usually determined by the used powder fraction and the particles’ melting degree. Using wires as feedstock material allows for a certain influence on the particle size distribution by adjusting process parameters. In this study, the influence of nozzle geometry and atomizing gas pressure on coating quality, surface roughness and cost-efficient post-treatments of wire-arc sprayed Fe-based alloys with a wide hardness-range is investigated. To allow for easy transfer to real components, the sample geometry is based on real world examples of coatings for new components and repair of worn parts. Using adapted process parameters and air-flow, the surface roughness could be decreased to allow for a less time-consuming post-treatment by grinding. Especially in repair coatings for large area applications requiring a smooth surface finish, significant runtime and cost reductions are feasible.