A non-destructive inspection technique known as photoluminescence piezospectroscopy (PLPS) has been used to measure residual stresses in thermally grown oxide layers in TBCs subjected to thermal cycling at 1121 °C. YSZ topcoats were applied by atmospheric plasma spraying on cold-sprayed bond-coated Ni superalloy substrates. Residual stresses were analyzed as a function of thermal exposure. Changes in stress were used to indicate spallation and damage degree in the coating system.

The main objective of this study is to determine the optimum conditions for cold spraying a WC-Co nanopowder on aluminum alloy and carbon steel substrates. XRD tests were run on the powder and coatings to determine if phase changes occurred during spraying. Coating samples were evaluated via adhesion, corrosion, and wear testing. Cold spraying proved to be very competitive with conventional thermal spray techniques, producing thick, dense, hard WC-Co coatings on steel as well as aluminum with excellent tribological and electrochemical properties.

This study assesses the viability of producing electrically conductive carbon nanofiber (CNF) reinforced mullite coatings by thermal spraying. Mullite-CNF agglomerated powder was prepared by spray drying and was deposited on steel by atmospheric plasma spraying. The coatings obtained are characterized based on composition, structure, shape, thickness, and electrical conductivity and are compared with coatings produced from commercial mullite powder.

This study evaluates the corrosion and wear resistance of WC-Co coatings produced by cold gas and HVOF spraying. Three WC-Co cermet powders varying in cobalt content were deposited on aluminum alloy substrates by both methods. The powders were characterized based on microstructure, particle size distribution, and phase composition, and the coatings based on cross-sectional microstructure, phase composition, and Vickers hardness. The coatings are also compared based on the results of ball-on-disk, rubber-wheel, and electrochemical testing, which shows that CGS has several advantages over HVOF spraying for the deposition of WC-Co coatings.

The aim of this work is to determine whether local disordering plays a role in the bonding of FeAl intermetallic coatings produced by cold spraying. XRD analysis of the powder and coatings revealed superlattice peaks, indicative of an ordered intermetallic structure. Nevertheless, locally disordered structures were detected in the deposits by TEM imaging. This may be related to a deformation induced order-to-disorder transformation due to the high strains involved in cold spraying, which is supported by comparing the magnetic properties of the deposits with those of HVOF sprayed coatings produced using disordered ball-milled feedstock.

In the present study, spherical Ti-6Al-4V powders were cold sprayed on titanium, aluminum, and magnesium alloy substrates to investigate influences over a wide range of damping conditions and respective deceleration of impacting particles. Single impacts were produced via wipe tests and bonding was evaluated by cavitation testing followed by SEM examination of impact and fracture morphologies. The results show that better bonding is achieved for material combinations with similar properties due to high adiabatic shear instabilities that result in microfusion at the particle-substrate interface. In the case of dissimilar materials, the conditions for bonding can be reached in an intermediate stage, but bonded areas may later separate due to particle movement around the interface.

In this work, Al and Al-Al 2 O 3 coatings up to 8 mm thick were cold sprayed on AZ91D magnesium alloy substrates. Microstructure, microhardness, bond strength, and corrosion and wear resistance were studied to assess the viability of using these coatings to restore dimensionally degraded parts and protect them from further corrosion and wear.

Inconel alloy coatings have been obtained by means of Cold Gas Spray technology with a high efficiency. Alumina has been sprayed simultaneously achieving an homogeneous distribution along the deposit with a good cohesion between particles. Furthermore, the alumina particles were found to improve the spraying feasibility. A proper optimization of the spraying conditions has been carried out in order to obtain the lowest porosity as possible and good embedment of the alumina. Then, the mechanical properties as well as tribological and oxidation behavior have been characterized. Alumina behaves as reinforcement leading to an amelioration of the abrasive and friction performance. Regarding the oxidation and corrosion behavior, the coatings proved to withstand reasonably well up to 800°C and salt fog tests (5% NaCl solution at 35 °C) indicate durability up to 1000 h.

The plasma spray process is used to create titanium oxide coatings under the current stoichiometry of titania and titanium suboxides. This study used feedstock powder with Magnéli phases TinO 2n-1 , slightly reduced titania TiO 2-x , and rutile. A factorial design of experiments approach was used to better understand the influence of operational parameters on coating quality, in particular, the electric resistivity and the degree of oxidation of the titanium oxide during the spraying. Firstly, arc current intensity and stand-off distance were studied; the results show strong correlations between particle temperatures and the electric resistivity of the coating. Then, different plasma compositions were used in order to understand the influence of hydrogen in the formation of titanium sub-oxides. The hardness of the most significant coatings was analyzed.

Cold Gas Spray allows to extend the range of steel coating formulations in comparison with other thermal spraying techniques because the material doesn’t melt during process. The absence of processes of fast solidification implies the absence of tensile stresses in the coating and makes possible to obtain thick coatings becoming a new alternative to welding cladding processes for the restoration of surfaces with corrosion pitting, notched areas or welded zones with bad appearance and for the repair of porous casting, contractions or losses of tolerance, by applying located coatings. 17-4 PH steel is one of the most widely used precipitation hardening grades in the business, offering high strength with corrosion resistance similar to S30400 in most environments. While soft and ductile in the solution annealed condition, it is capable of high properties with a single precipitation or aging treatment. Characterized by good corrosion resistance, high hardness, toughness and strength. Commonly used in both aircraft and gas turbines, nuclear reactor, paper mill, oil field, and chemical process components. A study has carried out in Thermal Spray Center for the production and optimization of thick coatings of 17-4 PH steel (S17400) through Cold Gas Spray technology onto carbon steel substrates. The study concentrates in the determination of influence of spray parameters on coating properties.

Hydroxyapatite (HAp: Ca 10 (PO 4 ) 6 OH 2 ) is a biocompatible and bioactive ceramic material widely used as a coating on metal surfaces (dental implants, hip replacements ...), but the low adhesion between HAp and the substrate due to the differences in thermal expansion coefficients of both, and the degradation of HAp, is being improved through the addition of TiO 2 to reach a good combination of mechanical properties. Therefore, the objective of this project is to produce 80%HAp-20%TiO 2 (by weight) coatings on Ti6Al4V by High-Velocity Oxy Fuel (HVOF). The microstructure study has been carried out using scanning electron microscopy, and the characterization of the present phases, hydroxyapatite and rutile mainly, using X-ray diffraction and Raman spectroscopy (the last one to find out which are the minority phases, such as anatase and tricalcium phosphates). Also Rietveld method has been used to quantify the amount of amorphous phase, lower than in the case of plasma-sprayed coatings. The coatings adhesion has been measured by tensile tests according to ASTM C633-01(2008), finding an improvement over the adhesion of plasma sprayed coatings, and also of hydroxyapatite coatings; also their bioactivity has been evaluated through its immersion in simulated body fluid (SBF), and through in vitro tests to study osteoblast behaviour on the coatings surfaces, with positive results. To conclude, a discussion about the results is made to analyze the industrial viability of these kinds of coatings.

This paper investigates the oxidation that occurs during the flight movement of a powder particle and during the spatter solidification in the thermal spray process. The effects of oxidation on droplet flattening, on the mechanical and thermal interactions between spatter and substrate, on spatter morphology, on porosity, and on adhesion are studied. The influence of wetting and oxygen dissolution is analyzed. The experimental results show that during High Velocity Oxy-Fuel spraying of the chromium carbide-nickel-chromium powder, the relative mass of chromium oxide in the coating is about 4.95%. The theoretical results agree well with the experimental observations. Paper includes a German-language abstract.