16 juil
16/07/2020 09:00

Sciences & Société

Soutenance de thèse en visioconférence : Elizaveta LAPUSHKINA

Soutenance d'une thèse de doctorat en cotutelle internationale entre l’Université de Tohoku (Sendai, Japon) et l’INSA Lyon

Anti-Corrosion Coatings Fabricated by Cold Spray Technique: Optimization of Spray Condition and Relationship Between Microstructure and Performance 

Doctorante : Elizaveta LAPUSHKINA

Laboratoire INSA : MATEIS

Ecole doctorale : ED34 : Ecole Doctorale Matériaux de Lyon

Anticorrosion coatings have been deposited with Cold Spray method from Zinc and Aluminium powders. While zinc coatings deposition the optimization of spraying parameters were performed and the most influence parameters of gas temperature and pressure defined. Doehlert uniform shell design have been proposed for theoretical prediction of the properties of not deposited coatings based on samples with neighbor conditions. Influence of gas temperature and pressure on coating microstructure, porosity, thickness and corrosion resistance was described. Different sets of parameters enable two protection modes were found: the sacrificial mode for heterogeneities in the coating (290 °C and 3.0 MPa), and corrosion product protection for homogeneous and dense coatings (320 °C and 2.5 MPa).
The mechanism of corrosion was studied and described as conditioned by corrosion initiated by roughness and corrosion propagation through interlamellar microstructure controlled by an adiabatic shearing. The set of parameters with temperature of 320 °C and pressure 2.5 MPa provided the highest corrosion performances of Zn cold spray coatings.
The influence microstructure and heterogeneities of zinc coatings on electrochemical behavior were studied with electrochemical 3-electrode cell at micro scale. It was concluded, that different area of heterogeneities at the exposed surface can shift corrosion potential and current density. However, the influence is not crucial taking into account the influence of possible oxygen penetration with following change in pH value.
Aluminium coatings have been deposited with low pressure cold spray method. Optimal spraying parameters according to deposition efficiency was found 400 °C /0.65 MPa. Ceramic particles have densified the coating and allowed to reduce porosity from 8% to 6.4%. Laser treatment did not perform coating melting, however, it released coating microhardness due to relaxation of residual stresses and possible change in microstructure. Composite coatings have shown higher corrosion resistance than both pure aluminum and laser-treated coatings.