ADHESION AND DURABILITY PERFORMANCE OF PLASMA-SPRAYED POLYMERIC COATINGS ON TITANIUM

摘要

Titanium-6 A1-4V panels were grit blasted with alumina, silica, or chromia grit and plasma-sprayed with one of four polyimide powders. The coatings were porous, but covered the titanium substrate in most instances. SEMs of the plasma-sprayed coatings indicates that some melting and agglomeration of the particles occurred. The specimens were bonded as lap shear samples using a commercial glass scrim cloth supported polyimide adhesive. Specimens were tested as made or after three days in boiling water. The lap shear strengths were approximately 5000 psi for alumina and chromia grit blasted samples tested as made, with the exception of chromia/LaRC-SI, which was about 4200 psi. After three days in boiling water the lap shear strengths dropped to around 3000 psi for alumina grit blasted samples, and 1500 psi for chromia grit blasted samples. Samples grit blasted with silica showed lower lap shear strengths for both as made and water boil conditions. Failure was primarily adhesive for chromia and silica grit blasted samples. Alumina grit blasted samples showed more cohesive failure when tested as made, but adhesive failure after immersion in boiling water. Surface analysis indicates that the areas which appear to show adhesive failure may in fact have failed within the polyimide coating.