種々の電気化学的手法によるセラミックコーティング膜の欠陥評価(<小特集>先進材料と信頼性解析・評価)

概要

論文の詳細を見る
Pinhole defects in two different TiN films were evaluated by conducting tests employing various electrochemical methods. TiN-coated stainless steels prepared by plasma CVD are best evaluated by electrochemical measurements under the coupling condition between specimen and counter electrode of Pt, because there is little spalling-off of the coated film in this evaluation method. On the other hand, TiN coated steels prepared by dynamic ion mixing can be examined using potential sweeping electrochemical measurements, such as the critical passivation current density (CPCD) method and polarization curve method, because there is sufficient adhesive strength between the substrate and the coated film. Then, the CPCD method was applied for evaluation of the defects in plasma-sprayed ceramic coating whose thickness is more than 200 μm. The corrosion damage of plasma-sprayed ceramic coating was brought about by the anodic dissolution of the undercoated NiCrAlY layer at the boundary between the zirconia top coat and the undercoated layer. Therefore, the ratio of the ratio of the undercoated layer's damage, that is the defect ratio of top-coated layer, due to corrosive solution penetrating the inner layer through the top coat layer can be evaluated through the CPCD method.
1995-09-25