MICROSTRUCTURE OF PLASMA-SPRAYED TAC COATINGS

TaC coatings were plasma-sprayed in a controlled argon atmosphere. The microstructure of the coatings was determined by scanning electron mi croscopy and transmission electron microscopy. All the lamellae in the coating are formed by a mosaic of columnar grains normal to the inter face, perfectly polygonized and jointed. This microstructure can be ex plained by a crystal growth mechanism in the solid phase (a grain grow th mechanism) starting immediately after the solidification of the fir st lamella.