In cold spray, innovative coating process, powder particles are accelerated by a supersonic gas flow above a certain critical velocity. Particles adhesion onto the substrate is influenced by particle impact velocity, which can change dramatically depending on particle position from the core of the jet. In the present work, an original experimental set-up was designed to discriminate the particles as a function of the levels of velocity to investigate the influence of this parameter on adhesion. Particles at given positions could therefore be observed using scanning electron microscope, which showed different morphologies as a function of impact velocity. High pressure and temperature at the interface during impact were calculated from numerical simulations using ABAQUS Ò . Transmission electron microscope analyses of thin foils were carried out to investigate into resulting local interface phenomena. These were correlated to particle impact velocity and corresponding adhesion strength which was obtained from LAser Shock Adhesion Test.

Thermally sprayed ceramic coatings such as plasma-sprayed alumina exhibit a composite microstructure actually due to the presence of defects such as pores, interlamellar and intra-lamellar cracks. These second phasetyped features influence the mechanical behaviour of the coating dramatically. In this study, a microstructure simulation of plasma-sprayed alumina was developed for the optimizing of component properties such as electrical tool used in the oil industry. This approach consisted of a finiteelement analysis of mechanical properties from simulated microstructures. Several composite microstructures were tested from air plasma spraying of alumina. Various degrees of porosity and cracks could be obtained from different spraying conditions. Every composite microstructure was studied using a quantitative image analysis of scanning electron microscope (SEM) cross-sections. A finite-element model based on the actual microstructure was developed. First, two-dimensional (2D) finite elements meshes were created from SEM images of microstructures. Then, in order to have a realistic representation of the three-dimensional (3D) microstructure, pictures were obtained using X-ray microtomography. Volume tetrahedral grids were generated to simulate the properties of alumina coatings. This work studies the contribution of every part of the alumina coating to the final properties and shows potentials and limitations of the 2D and 3D computational approach.