Influence des conditions d'impact sur l'adhérence de cuivre projeté dynamiquement sur de l'aluminium

In cold spray, innovative coating process, powder particles are accelerated by a supersonic gas flow above a certain critical velocity and kept in a solid state until impact. Coating results from the pile up of particles and its quality depends on particles adhesion. In this work, adhesion of the first particles impacted onto the substrate, namely splats, was studied as a function of their impact conditions. Indeed, particles adhesion onto the substrate is influenced by oxidation, particle impact velocity and temperature, which can change dramatically depending on spraying conditions. For this purpose, a method was developed to correlate spraying conditions to impact conditions using experimental sets up and numerical simulation. High pressure and temperature therefore induced at the interface during impact were calculated from numerical simulation. Transmission Electron Microscope analyses of thin foils were carried out to investigate into resulting local interface phenomena. These were correlated to particle impact conditions and corresponding adhesion strength which was obtained from LAser Shock Adhesion Test (LASAT).Lors de la projection dynamique par gaz froid, nommée " cold spray ", les particules sont accélérées aérodynamiquement et maintenues à l'état solide jusqu'au moment de l'impact sur le substrat. L'empilement de ces particules constitue le revêtement dont l'adhérence représente un paramètre déterminant quant à la qualité des pièces industrielles. L'enjeu de cette étude est la compréhension et la quantification de l'adhérence interfaciale par l'analyse de la phase d'accrochage des premières particules dispersées à la surface du substrat, en fonction des conditions d'impact. Vitesse d'impact, température de préchauffage et oxydation des surfaces mises en contact ont, en effet, une influence directe sur les phénomènes survenant à l'interface donc sur l'adhérence. Cette étude propose une méthode permettant de relier les conditions de projection aux conditions d'impact, aux mécanismes survenant entre la particule et le substrat durant l'impact et, enfin, au niveau d'adhérence des particules correspondantes. Pour cela, les conditions d'impact ont été déterminées par l'utilisation conjointe de techniques expérimentales et de modélisations numériques. Les températures locales et les pressions de contact alors induites à l'interface durant l'impact ont été calculées par simulation numérique. Des analyses fines par transmission ont été réalisées afin d'étudier les phénomènes survenant le long de l'interface, en fonction des conditions d'impact. Enfin, les niveaux d'adhérence correspondants ont été obtenus par une utilisation originale de l'essai LASAT (LAser Shock Adhesion Test). Les phénomènes responsables de l'adhésion ont ainsi pu être mis en évidence et leur influence quantifiée

Influence des conditions d'impact sur l'adhérence de cuivre projeté dynamiquement sur de l'aluminium

Lors de la projection dynamique par gaz froid, nommée " cold spray ", les particules sont accélérées aérodynamiquement et maintenues à l'état solide jusqu'au moment de l'impact sur le substrat. L'empilement de ces particules constitue le revêtement dont l'adhérence représente un paramètre déterminant quant à la qualité des pièces industrielles. L'enjeu de cette étude est la compréhension et la quantification de l'adhérence interfaciale par l'analyse de la phase d'accrochage des premières particules dispersées à la surface du substrat, en fonction des conditions d'impact. Vitesse d'impact, température de préchauffage et oxydation des surfaces mises en contact ont, en effet, une influence directe sur les phénomènes survenant à l'interface donc sur l'adhérence. Cette étude propose une méthode permettant de relier les conditions de projection aux conditions d'impact, aux mécanismes survenant entre la particule et le substrat durant l'impact et, enfin, au niveau d'adhérence des particules correspondantes. Pour cela, les conditions d'impact ont été déterminées par l'utilisation conjointe de techniques expérimentales et de modélisations numériques. Les températures locales et les pressions de contact alors induites à l'interface durant l'impact ont été calculées par simulation numérique. Des analyses fines par transmission ont été réalisées afin d'étudier les phénomènes survenant le long de l'interface, en fonction des conditions d'impact. Enfin, les niveaux d'adhérence correspondants ont été obtenus par une utilisation originale de l'essai LASAT (LAser Shock Adhesion Test). Les phénomènes responsables de l'adhésion ont ainsi pu être mis en évidence et leur influence quantifiée.In cold spray, innovative coating process, powder particles are accelerated by a supersonic gas flow above a certain critical velocity and kept in a solid state until impact. Coating results from the pile up of particles and its quality depends on particles adhesion. In this work, adhesion of the first particles impacted onto the substrate, namely splats, was studied as a function of their impact conditions. Indeed, particles adhesion onto the substrate is influenced by oxidation, particle impact velocity and temperature, which can change dramatically depending on spraying conditions. For this purpose, a method was developed to correlate spraying conditions to impact conditions using experimental sets up and numerical simulation. High pressure and temperature therefore induced at the interface during impact were calculated from numerical simulation. Transmission Electron Microscope analyses of thin foils were carried out to investigate into resulting local interface phenomena. These were correlated to particle impact conditions and corresponding adhesion strength which was obtained from LAser Shock Adhesion Test (LASAT).PARIS-MINES ParisTech (751062310) / SudocSudocFranceF

The influence of the substrate on the deposition of cold sprayed titanium : an experimental and numerical study

International audienceThe deposition of cold-sprayed titanium on various substrates is studied in this work. A rather coarse powder of titanium (−70 + 45 μm) was sprayed under uniform spraying conditions using a cold spray system onto five different substrates: two aluminum-based alloys (AISI 1050-H16 and AISI 2017-T4), copper, stainless steel AISI 304L, and Ti-6Al-4V. All the spraying experiments were carried out using alternatively nitrogen (N2) or helium (He) as the process gas. Thick coatings were formed on the various substrates, with the exception of the AISI 2017 substrate. When N2 was used as the process gas, only a few particles remained adhering to the AISI 2017. The thick pre-existing superficial oxide layer on AISI 2017, which was detected by Electron MicroProbe Analysis (EPMA), appeared to prevent adhesion of cold-sprayed titanium particles. The interaction of the sprayed particles with the various substrates was also studied by means of numerical simulations to better understand the adhesion mechanisms. The microstructure and the characteristics of the coatings were investigated. Deposition efficiency and coating density were found both to be strongly improved by spraying helium as the process gas

CODLIS (Coating Deposition using Laser Induced Spallation)

International audienc

Projection dynamique par gaz froid

National audienc

Les applications en projection dynamique par cold spray (série 2/2)

National audienc

Cold spraying combined to laser surface pre-treated using PROTAL

International audienc

Lasers and thermal spray

International audienceBasically, thermal spray and laser processing can be considered as half brothers since they show many common features due to the use of a (more or less) high-energy source for both. Their combination can therefore be very fruitful and prominent to achieve coatings, which results in their most recent and advanced applications. In the materials processing development story, the laser will thus have moved from cutting to coating. This keynote presentation focuses on the recently-developed coupling of laser processing to cold spray). In this dual process, a cold spray gun is combined to a laser head in a single device, e.g. on a robot. Series of coating experiments using various laser irradiation conditions, primarily pulse frequency, were carried out for Al-based and Ni-based alloys. Laser pre-treatment of the substrate just prior to cold spray, was shown to be beneficial for adhesion of cold-sprayed coatings. Adhesion improvement was exhibited and studied from LASATesting (LASAT for “LAser Shock Adhesion Test”). Incidentally, through LASAT also, the role of lasers in the development of thermally-sprayed coatings can be considered as major. Results are discussed in the light of a TEM (Transmission Electron Microscope) study of the coating-substrate interface with and without laser pre-treatment

A Socratic approach to surface modification: The example of Thermal Spray

International audienc

A Socratic approach to surface modification: The example of Thermal Spray

International audienc