INHOMOGENEITIES IN PLASMA-SPRAYED COATING OF THE CONICRALYTA TYPE

The coating produced by plasma spraying is not homogeneous. It contains pores, an interface between substrate and coating, an interface between lamellae; particles of various size and deformation grade are deposited non-uniformly, the distribution of chemical elements in the particles is not uniform and, in some particles, following the transition through the plasma the elements due to reactions with the surrounding environment undergo a pronounced redistribution. On the CoNiCrAlTaY powder changes were examined on powder particles that arose after their transition through the plasma. A marked redistribution of elements occurs primarily in small particles (approximately up to 20 mum). Obviously complex oxides are formed, predominantly of the type: Al, Cr and Ta. The increased Al, Ta and Cr content in definite particle domains and thus also in the coating will imply their reduction in other domains. Thence follows the non-uniformness of coating properties and a non-uniform coating resistance to the degradation effects of the environment.