Blade coating delamination is defined as the separation of protective coating from the substrate, and it is detected by:

• A. Ultrasonic thickness measurement only.
• B. Visual inspection, borescope, and sometimes eddy-current or laser scanning.
• C. Fuel system pressure tests.
• D. Visual color change under UV light only.

Answer: (B)

Delamination is a separation of the protective coating from the blade substrate, which often manifests as peeling, blistering, or thinning in the coating. Detecting it requires methods that reveal surface and near-surface changes. Visual inspection catches obvious peeling or coating loss on exposed areas, and a borescope lets you inspect internal blade faces and hard-to-reach features where delamination can occur without visible outside signs. When the problem is subtle or behind the surface, non-destructive techniques like eddy-current testing or laser scanning can detect near-surface disbondment or map coating thickness to identify areas where the coating has separated. Ultrasonic thickness measurement primarily gauges coating thickness and may miss disbondment that isn’t accompanied by a clear thickness change. Fuel system pressure tests aren’t related to coating integrity, and relying only on UV color changes can miss many delaminations. So the combination of visual inspection, borescope, and, when needed, eddy-current or laser scanning provides the most reliable detection of blade coating delamination.