WC-Co cermet powders were deposited on aluminum substrates by cold gas spraying. XRD tests were run on the powder and coatings to reveal possible phase changes during spraying. Bonding strength, abrasive wear resistance, and corrosion resistance were also measured and are compared with values obtained from HVOF sprayed WC-Co coatings.

This study investigates the impact behavior and consequences for coating formation in cold spraying of FeAl intermetallic compound powder. A range of spraying conditions was used to process single impacts in so-called wipe tests and for processing spray layers. In order to avoid brittle failure, high process gas temperatures and varied traverse speeds were used to account for thermal softening of spray particles and already adhering layers. Morphologies of as-impacted particles and partially removed single splats were subsequently investigated by SEM. The study of spray lines indicates that secondary impacts are only successful within an extremely narrow range of impact conditions. Within this narrow parameter regime, thicker and dense coatings are obtained. Hardness testing shows that the properties of the powders were retained.

This study evaluates a method for producing carbon fiber composite feedstocks suitable for cold gas spraying. Powders consisting of Al-Si particles and carbon nanofibers were attrition milled at 16.5 Hz and 27.5 Hz for up to 12 h at room and cryogenic temperature. Particle shape and size were examined every hour and carbon fiber integration in the Al-Si matrix was assessed. Detailed results are presented and discussed. In all cases, cryomilled powders had smoother surfaces.

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.

Iron aluminides have been lately proposed as promising materials for wear applications. Many authors have focused their investigations on the friction behaviour of FeAl coatings emphasizing the role of this intermetallic as a new matrix to embed ceramic particles and replace for high temperature the extensively studied WC-Co cermet system. However, few works deal with the evaluation of the different tribological properties and their relationship with the coating microstructure. Thus, in the present study, the near stoichometric Fe40Al was successfully sprayed by means of HVOF using different spraying parameters and the tribological behaviour was assessed through solid particle erosion, abrasive and dry sliding tests. The wear mechanisms that took place in the produced coatings are discussed with regard to the obtained results. The friction coefficient versus sliding distance was obtained. In addition, isothermally treated samples in air were tested showing both lower friction coefficient and lower wear rate.

Hydroxyapatite (HAp) is known to be bioactive, i.e. able to bond to bone. This makes HAp very suitable to be applied as coatings on bone-metallic implants. In this work high velocity oxy-fuel spraying (HVOF) was used successfully for obtaining hydroxyapatite coatings on Ti-6Al-4V substrates. With optimized HVOF process parameters, coatings with similar bond strength to plasma sprayed HAp coatings, good microstructure and higher crystallinity degree than atmospheric plasma sprayed ones were obtained. As-deposited HAp coatings contains amorphous calcium phosphate (ACP) that can be crystallized by a heat-treatment of 60 minutes at 700 °C, resulting in a more stable coating when they are immersed in simulated body fluid (SBF).Coating structural characteristics of as-sprayed and post heat treated coatings were analysed with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy analyser (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Furthermore, in vitro tests were done in order to evaluate the coating response. Surface changes were observed for as-sprayed coating but not after a post heat treatment. Moreover, the strength of the coatings were evaluated after in vitro leaching. The high degree crystallinity of the post heat treated coating improves the adhesion between the coating and the substrate after an in vitro test in a free-protein simulated body fluids (SBF). Consequently a relation between the amorphicity, the in vitro response and mechanical degradation of the coating was found.

Biomaterial coatings must have high degrees of crystallinity and phase purity, good adhesive and cohesive integrity and adequate porosity to promote bone ingrowth. The most used coating method is atmospheric plasma spraying. However, the main drawback of this technique is the generation of an amorphous phase and other calcium phosphate phases after the spraying process, which are not present in the feedstock and are not desirable. The use of HVOF as a process for obtaining hydroxyapatite coatings on Ti-6Al-4V was used successfully. With optimised HVOF process parameters, coatings with similar bond strength to plasma sprayed HAp coatings, good microstructure and higher crystallinity degree than atmospheric plasma sprayed ones where hydroxyapatite was the only crystalline phase present were obtained. Coating characteristics were analysed with XRD, EDS, SEM, FTIR which indicated that the coatings had a high degree of crystallinity and good bond strength. Moreover, in vitro response were also evaluated and the strength of the coating to the substrate.

The growing use of thermal spray technology in manufacturing is increasing the need for knowledge regarding the behavior of thermal spray coatings in aggressive environments. Due to the different characteristics of the spraying processes and materials used, the mechanisms of attack can vary greatly from layer to layer depending on the application. This paper presents a detailed investigation of corrosion mechanisms at room temperature and their effect on a wide range of thermally sprayed metals and ceramic-metal (cermet) composites. Paper includes a German-language abstract.

Results of experimental studies are presented which address a concern that gallium staining from FIB imaging during backside editing might degrade IR navigation as well as signal acquisition during probing of flip chips by such techniques as Picosecond Imaging Circuit Analysis (PICA) and Laser Voltage Probing (LVP). Although optical transparency does depend on gallium implantation dose, Ga staining is, however, not necessarily a limitation to the implementation of photon optical tools in the debug laboratory. Comparisons are made on the results from devices under the following conditions: with and without an anti-reflective (AR) coating, with and without XeF2 enhancement during FIB etching, and with confocal laser scanning microscope (CLSM) imaging and CCD-based IR microscope imaging.

Thermal spray coatings as Cr 3 C 2 -NiCr obtained by high velocity oxy-fuel spraying (HVOF) are mainly applied due to their behaviour against aggressive erosive-abrasive and corrosive atmospheres and their thermal stability at high temperatures. In order to increase the corrosion protection that it offers to the substrate trying to close the interconnected pores, it is possible to apply a thermal treatment with the gun during the spraying of the coating. This treatment could be applied in different ways. One of these ways consists of spraying only a few layers of coating followed by thermal treatment and finally the spray of the rest of layers. This thermal treatment on spraying is studied related to the corrosion properties of the system. The study comprises the electrochemical characterisation of the system by open circuit potential (OC), polarisation resistance (R p ), cyclic voltammetry (CV) and impedance spectroscopy measurements (EIS). Optical and scanning electron microscopy characterisation (OM and SEM) of the top and cross-section of the system has been used in order to justify the electrochemical results.

This paper presents the electrochemical characterization of a chromium carbide-NiCr coating applied using high-speed flame spraying. It examines the behavior of the complete system, the steel, the steel coating, and the coating immersed in NaCl solution alone. The paper discusses electrochemical measurement methods such as the measurement of polarization resistance, anodic polarization, and open circuit potential. The tests are compared with each other and with results from metallographic examinations. The structure was characterized by light and scanning microscopy. In addition, an analysis of the residual water was carried out using an ICP technique. The paper also includes a study of the various mechanisms that could affect the behavior of such coating types in a corrosive environment. Paper includes a German-language abstract.