THE INFLUENCES OF HEAT-TREATMENTS AND INTERDIFFUSION ON THE ADHESION OF PLASMA-SPRAYED NICRALY COATINGS

Most coatings are applied with a specific aim in mind, such as improvi ng the base material resistance to corrosion or wear, or providing a b arrier against high temperatures. These aims can obviously only be ach ieved if the coating is properly bonded to the substrate. This study i s focused on a NiCrAlY metallic bonding layer and its adhesion on to n ickel-based superalloy substrate. It also looks at the influence of di fferent spraying methods (atmospheric plasma spraying and vacuum plasm a spraying) and the influence of a post-heat treatment on adhesion of the coatings. In order to determine adherence, a Vickers indentation t est was performed at the substrate/coating interface. In each case, th e residual stresses were evaluated by a step-by-step hole drilling met hod and these were taken into account in assessing the adhesion parame ters. The results were supplemented by a microstructural study of the interface.