Describe the process for coating removal and restoration of hot-section components during overhaul.

• A. Sandblast and immediately install new coating without inspection
• B. Ignore coating and reuse old coating
• C. Apply paint randomly
• D. Remove old coating with approved methods; inspect substrate; apply new thermal barrier coating per OEM; cure/bake per spec

Answer: (D)

Coating removal and restoration of hot-section components must follow a controlled sequence that protects the metal and ensures reliable thermal protection. Start by removing the old coating using methods approved for the specific coating system and substrate. These approved methods are chosen to clean the surface without introducing damage or residual contamination that could compromise future bonding.

After removal, inspect the substrate thoroughly for cracks, pitting, oxidation, or other damage that could affect performance. If any defects are found, address them per the overhaul manual or OEM guidance, repairing or replacing parts as required. Only when the substrate is sound should you proceed to recoat.

Apply a new thermal barrier coating exactly as the OEM specifies, selecting the correct coating system, material, thickness, and application method. This ensures compatibility with the engine’s materials and operating temperatures, and that the coating provides the intended thermal protection.

Finally, cure or bake the coating per the specification to achieve proper adhesion, density, and thermal properties. After curing, perform post-application inspections to verify coating thickness, integrity, and adhesion. This sequence prevents failures in service and maintains engine reliability.