This study investigates the effects of spark plasma sintering (SPS) on the microstructure and properties of cold-sprayed metallic coatings. Water-atomized Cu powder was deposited on Al 5052 substrates by high-pressure cold gas spraying, and the resulting coatings were treated by spark plasma sintering and annealing heat treatment (AHT) at 200°C, 300°C, and 400 °C. To assess the effects of diffusion generated by pulsed dc power, a vertical load was not applied in the SPS system. In addition, a short duration time was used to inhibit crystal grain growth. Treated specimens were evaluated by SEM, EBSD, and hardness and tensile testing. The findings show that the microstructure and hardness of SPS specimens treated at 300 °C are close to that of AHT specimens treated at 400 °C. Tensile strength, however, is clearly higher in the SPS300 specimens, indicating that pulsed dc power accelerates particle interdiffusion due to Joule heating and electromigration, thereby increasing adhesion strength between particles in the coating.

In this paper the influence on the coating generation of substrate preheating during spraying, relative movements torch to substrate and cooling conditions is systematically studied for partially stabilized zirconia and alumina coatings. Beads and coatings are sprayed with Ar-H 2 dc plasma jets in air. The obtained structure, resulting hardness and adhesion/cohesion for each spraying condition is discussed.

The influence of alumina substrate temperature and phase structure : columnar gamma phase, columnar alpha phase and granular alpha phase on splat formation and crystal growth has been studied by SEM and Atomic Force Microscopy. X Ray Diffraction at low angle has allowed to obtain informations on phase structure of layered splats according to substrate phase structure and coating thickness. Column sizes of splats are correlated to a ID model of splat cooling showing the influence of substrate thermal properties and splat thickness on crystal growth kinetic. Finally, coatings adhesion-cohesion values function of spraying parameters are in good agreement with splat morphology and microstructural evolution.