Which repair process is used to restore blade roots?

• A. Electron beam welding
• B. Plasma coating
• C. Plasma Spraying
• D. Laser cladding

Answer: (B)

Restoring a blade root means adding material exactly where wear or damage has reduced the root’s cross-section, so the shape and strength of the root can be brought back to specification and finished to the required dimensions. Plasma coating does that by depositing a dense, adherent layer onto the root area, allowing controlled buildup of material where needed. This approach reestablishes the original geometry and provides a good surface for final machining while keeping heat input relatively moderate, which helps minimize distortion in a critical high-stress region. After coating, the root can be ground to final size and surface finish, and the coating itself offers protection where the root is exposed to harsh service conditions.

Electron beam welding, by contrast, relies on melting metal to join or fill areas, which introduces higher heat and can cause distortion or microstructural changes in the delicate root region. Plasma spraying deposits coatings but may not provide the same level of metallurgical bond or precise buildup required for restoring root thickness. Laser cladding also builds up material with a laser, but the localized, intense heat can introduce residual stresses and distortion in the root area.