Oxydation par plasma électrolytique : influence des paramètres du procédé sur le comportement des micro-décharges et conséquences sur les couches d'oxydes

Abstract : Plasma electrolytic oxidation is a surface treatment process applied to light weight alloys (Al, Mg, V, Ti, etc.) which may advantageously replace conventional anodizing, especially regarding environmental issues. Though this process has been known for many years, the underlying mechanisms that govern this micro-discharge assisted process remain poorly understood. This work aims at better identifying the breakdown and development mechanisms of the micro-discharges and at correlating the micro-discharge characteristics to the properties of the layers grown onto Al2214 aluminium alloy samples. The approach consists in coupling the study of the micro-discharges, the characterization of the grown layers and the breakdown mechanisms. By means of high rate video recording (> 125 000 frames/s) and shadowgraph techniques, the dependence of the evolution of the micro-discharges with the macroscopic process parameters has been clearly established. The important role of counter-electrodes and their respective position with respect to the sample have been identified and studied. It is also shown that the suitable choice of current frequency and anodic current density may greatly improve the quality of the resulting oxide layers. Current frequency in the kHz range seems most appropriate to grow thick and defect-free homogeneous layers.Finally, from synchronous measurements, it has been pointed out a delay in the onset of micro-discharges with respect to the rising edge of the current pulses. Besides this delay is strongly sensitive to the process parameters, it is probably related to the breakdown mechanisms of the insulating layer. Scenarios for these mechanisms have been proposed.
Document type :
Theses
Complete list of metadatas

Cited literature [14 references]  Display  Hide  Download

https://hal.univ-lorraine.fr/tel-01749516
Contributor : Thèses Ul <>
Submitted on : Thursday, March 29, 2018 - 12:18:28 PM
Last modification on : Tuesday, August 21, 2018 - 9:46:04 AM
Long-term archiving on : Friday, September 14, 2018 - 7:17:14 PM

File

INPL_2011_MELHEM_A.pdf
Files produced by the author(s)

Identifiers

  • HAL Id : tel-01749516, version 1

Citation

Amer Melhem. Oxydation par plasma électrolytique : influence des paramètres du procédé sur le comportement des micro-décharges et conséquences sur les couches d'oxydes. Autre. Institut National Polytechnique de Lorraine, 2011. Français. ⟨NNT : 2011INPL098N⟩. ⟨tel-01749516⟩

Share

Metrics

Record views

32

Files downloads

88