The use of helium with the cold spray process is well-known to give a higher velocity to the particles and thus denser coatings than those obtained with the classical use of nitrogen. The LERMPS-UTBM laboratory has developed a unique system to use helium without losses. The spray process occurs in a LPPS tank and a specific closed circuit including the cooling and filtering of helium allows its circulation. The spray operations can be made at low helium pressure with no pollution by oxygen. The control device allows to work with different pressures and gas temperatures at the torch with the same tank pressure. Helium gas flow can reach 180 Nm 3 /h and current cold spray torches could be used. The circulation and reuse of helium in a closed circuit result in a very low consumption of helium. The first coatings of copper alloys are presented in this work.

Thermal fluxes transferred during HVOF thermal spray have an important influence on the thermal history of the work-piece. Thus, there is an interest in quantifying these fluxes. Today, different studies based on the use of calorimeters were proposed in the literature and CFD calculations may also be used to confirm the measures. In the present study, a new method based on the measurement of the transient increase of the work-piece temperature was used in order to estimate the thermal exchanges between an HVOF jet impinging on different diameter cylinders. The results indicate that fluxes of several MW/m 2 may be transferred depending on the standoff distance, spray parameters and gun.

Inconel thermal spray coatings are potential candidates for wide industrial applications. However, the coating structure resulting from thermal spray processes characterized by unmelted particles, oxides and porosity can severely hinder their corrosion resistance in aggressive media. The aim of the present work was to optimize elaboration parameters in order to enhance their chemical stability. Electrochemical criteria were used to identify the ability of those coatings to form a passive film in a sulfuric acid solution and also to determine their local corrosion resistance in a chloride solution. Results show that the passivity state is strongly conditioned by the coating microstructure. Coatings free of unmelted particles exhibit a notably reduced passive current density while the localized corrosion resistance seems conditionned by the amount of interlamellar oxide.

This paper is dedicated to the comparison of experimental and numerical results obtained on iron particles characteristics during plasma spraying. Each part of the spray process (particle injection, behavior of the particle in the plasma jet and coating formation) may be studied using appropriate diagnostic techniques. In the present work, on-line measurements of in-flight particle characteristics were performed using an optical diagnostic technique insuring a real time control of temperature, velocity and diameter of particles during the spray process. Besides, numerical results were obtained considering momentum and thermal exchanges between the plasma jet and particles using an Eulerian-Eulerian model. The evolution of velocity and temperature with the particle size given by in-situ measurements were then correlated to those obtained with the numerical code.