What is a common strategy to prevent galling of bolts in nuclear assemblies?

• A. Use identical, hard coatings only.
• B. Use compatible alloys, proper lubrication, coatings, and optimized surface finishes.
• C. Avoid lubrication to prevent contamination.
• D. Increase bolt diameter without changing materials.

Answer: (B)

Galling happens when metal surfaces seize and cold-weld under high contact stress, especially in high-strength bolts in tight joints. The most reliable way to prevent it is to address all the practical controls at once: choose compatible alloys so the mating parts Don’t have a strong tendency to adhere or diffuse into each other; use proper lubrication to lower friction and prevent metal-to-metal sticking; apply coatings to create a barrier between surfaces and sometimes include solid lubricants; and optimize surface finishes to minimize roughness and asperities that seed sticking. Together, these measures reduce adhesion and wear in the interface, keeping threads from seizing under load. Relying on a single tactic (like just a hard coating or no lubrication) or making the bolt larger without addressing materials and surface condition doesn’t adequately prevent galling.