Modification of ceramic thermal spray deposit microstructure implementing laser treatment

摘要

Microstructural features such as cracks, pores and delaminations are known to significantly affect the properties of thermal spray ceramic coatings. As an example, tensile properties depend mostly on the size, the shape and on the degree of clustering of pores since highly clustered porosity generates regions of poor mechanical properties from where cracks easily propagate through the entire volume. Another example concerns the corrosion resistance of coated components which is significantly degraded when pores are connected. To circumvent such disadvantages, several post-treatments may be implemented. The most commonly used is sealing of pores by impregnation using either low melting temperature metallic alloys or organic materials. In addition to be a costly additional step to the deposit manufacturing process, the coating working temperature limit is significantly reduced. Therefore, numerous works along the twenty past years have been devoted to find ways to densify ceramic coatings. Among these treatments, the use of high energy laser beams was very often considered. This paper aims to bring a contribution to those efforts by presenting results concerning the laser treatment of zirconia thermal spray coatings.