The purpose of the metal spray rub coating on the rotor and stator casing of an axial type compressor is which of the following?

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

Metal spray rub coatings are sacrificial layers applied to casings to allow for tight tip clearances. During operation, the blades may lightly abrade this coating, creating a custom fit that minimizes gas leakage over the blade tips, thereby maximizing compressor efficiency and preventing aerodynamic stall conditions.