The purpose of the metal spray rub coating on the rotor and stator casing of a marine type gas turbine is to _________.

Correct Answer: Option B — provide close vane to rotor and blade to stator case clearances

Metal spray rub coatings are applied to turbine casings to allow for extremely tight clearances between rotating blades and stationary components. During operation, the blades may lightly abrade the coating, creating a custom-fit seal that minimizes gas leakage and maximizes aerodynamic efficiency without damaging the expensive turbine rotor blades.