In this work, a numerical model of the cold spray process was developed to reproduce microstructures obtained in coatings by simulating the deformation of impinging particles and resulting coating build-up. The model employs a library of particle images generated by x-ray microtomography. To each image, a velocity is assigned and the deformation that would be produced by particle impact is estimated by means of finite element analysis and stored for later use. Based on the results, the ing approach has good potential for simulating coating microstructures that can be achieved through cold spraying.

The homogeneity of thermal spray plumes is mostly dependent on the type of feedstock used. Powdery feedstocks, for example, promote homogeneity. If in-flight particles are atomized from a melting bath, however, as in twin wire arc spraying (TWAS), the spray jet is less homogeneous due to the fact that particles are generated by the impingement of an airflow on the melting tips of electrically conducting wires. This work aims to contribute to the understanding of the initiation of such particles in the TWAS process. To that end, cored wires filled with W-rich particles were sprayed, then the process was halted and the wire tips were examined to analyze how the filling powder interacts with the melted part of the velum. 3D tomograms show that the resolidified melt bath is interspersed with spherical and irregular-shaped W-rich particles. The irregular shape implies a partial melting of the W-rich particles.

In the present study, X-ray microtomography is used to examine cold-sprayed tantalum splats on copper substrates. To resolve tantalum splats intermeshed with other splats of the same chemical composition, a contrasting medium of some sort is required. For this purpose, the feedstock powder is coated with an iron layer by means of fluidized-bed chemical vapor deposition. Experimental tests were coupled with finite element simulations to determine how stresses generated during the impact of a spherical iron-coated particle affect the integrity of the added contrasting layer.

This paper describes the development of detonation-sprayed aluminum-matrix composite coatings reinforced with boron carbide. The goal is to achieve a homogeneous coating structure with low porosity, low oxide content, and high concentration of embedded carbides. Tensile tests of various types were conducted and different stages of deformation were analyzed using micro computed tomography, a 3D imaging technique that reveals the formation of cracks in real time.

This paper reviews some of the tools used to characterize the pore microstructure of thermally sprayed thermal barrier coatings. It describes the capabilities of optical and SEM analysis, intrusion porosimetry, high-flux X-ray and neutron imaging, small-angle scattering, and X-ray microtomography. It explains why it is often necessary to combine multiple techniques and provides examples showing where it has been done and what it can achieve. It also reviews commonly used porosity descriptors.

In this work, the microstructure of silver coatings obtained by cold spraying with a fine and a rather coarse powder were investigated. Cold-sprayed microstructures strongly depend on the deposition process parameters. These parameters have an influence on porosity, plastic strain, particle-to-particle bonding mechanisms. The originality of this study rests on the use of X-ray microtomography, which is shown to be a very powerful technique to investigate into cold-sprayed coatings. Several samples were machined from coatings by electro-discharge machining (EDM) then scanned using microtomography. Porosity fraction was determined by three-dimensional image analysis and compared to classical two-dimensional analysis of micrographs. A difference between the two methods was exhibited, which showed sample preparation effects. Consequently, X-ray microtomography seems to be well adapted to study cold-sprayed coatings thoroughly. Another result from this work was the characterization of the morphology of pores and deformed particles. Bonding mechanisms in cold spray could therefore be discussed. In addition, the knowledge on deformed particles allowed to simulate cold-sprayed coatings with build-up models. This will be done in a further work