Study of the interface strength and residual stresses within plasma sprayed alumina coatings involving LASAT (Laser Shock Adhesion Test)

Abstract : The study of both the interface strength and the residual stress within a ceramic coating obtained by plasma spray is of great interest to better understand the mechanical properties of metal/ceramic systems. In this work, experiments involving a LASAT facility (LASAT: Laser Shock adhesion test) were implemented in order to analyse the adhesion and the damaging behaviour (debonding and buckling) of alumina coatings onto Ni-based alloy. Similar alumina coatings were achieved using same plasma parameters with various surface preparations: smooth or severe grit blasting, with and without pre-oxidation and electro-discharge machining. From the non destructive analyses (Optical, and IR imaging) of the buckled region after LASAT, it allowed to compare and discuss the interface strength of the various coating samples. Further discussion was carried out by analysing the mechanical behaviour of the buckle region when stress release are induced within the coating after LASAT. From such original analysis involving a non invasive method like LASAT, it was evidenced that the residual stress state within a ceramic coating have an important role on resulting adhesive properties. From such explorating work, it is proposed to envisage the LASAT method to analyse both the adhesion and the residual stress within thermal spray coatings.