Caractérisaton des revêtements par projection thermique à haute vitesse obtenus à partir de différentes poudres de WC-10Co-4Cr pour des applications en aéronautique

Abstract

HVOF (High Velocity Oxy-Fuel) thermal sprayed coatings are commonly used in the aviation industry, particularly by the industrial partner of the project (Tecnickrome Aeronautique Inc) as a replacement for hard chrome electroplated coatings due to environmental problems. The aim of the project was to find a powder as an alternative to that currently used for the production of WC-10Co-4Cr HVOF thermal sprayed coatings obtained with the HVOF-JET KOTE® III thermal spray system. First, five powders, including a reference one, having different powder grain size distributions, were sprayed in order to identify which powders could be used with the HVOFJET KOTE® III thermal spray system, keeping similar parameters (hydrogen flow, oxygen flow, powder feed rate and stand-off distance) as for the reference powder. The coatings obtained from the studied powders were evaluated according to the coatings acceptance criteria requested by the main landing gear manufacturers. The tests included thickness, adhesion, microstructure, microhardness, residual stress and roughness. From the results, only two powders met all the properties required by the aerospace specifications. The influence of the stand-off distance on the quality of the coatings was studied. Five distances (100, 125, 150, 175 and 200 mm) were chosen to spray the two selected powders. The obtained coatings showed similar coating properties (thickness, adhesion, microstructure, microhardness, residual stress and roughness). It was found that stand-off distance is an indirect parameter of the HVOF-JET KOTE® III thermal spray system and that the velocity as the temperature of the particles seem to better determine the coating properties, in particular, the final residual stress in the coatings. When coatings are produced at lower levels of stand-off distance, particles arrive with higher velocity and temperature resulting in higher substrate temperature and higher impact energy, resulting in higher compressive residual stress in the coatings.

Date	9 Nov 2016
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Philippe Bocher (Supervisor)