Texture and residual stresses in thermally sprayed coatings

Abstract

The formation of texture and residual stresses in thermally sprayed pure metallic and alloyed coatings has been investigated, principally by X-ray diffraction methods. The materials studied were pure molybdenum and copper-, iron-, nickel- and cobalt-based alloys, applied by flame or plasma spraying. It was found that, in some cases, thermal spraying produced crystallographic texture whilst in others no preferred orientation was evident. Compressive residual were also found in some of the alloyed coatings. An analysis of the origins of texture was performed, based on consideration of the thermophysical and mechanical properties of the applied coatings. The assumed model predicts that in some cases there should be the formation of fibre texture, with the normals to the most closely-packed planes being aligned with the normals to the coated surface. The contribution of plastic deformation to the formation of compressive residual stresses in the alloyed coatings has also been considered.