· High-speed spindles, aerospace engines, machine tool spindles - low density (≈3.2 g/cm³ vs. 7.8 for steel) reduces centrifugal force and heat, enabling higher speeds (dn > 2×10⁶).· Vacuum, oil‑free, or corrosive environments - self‑lubricating, corrosion resistant, electrically insulating (prevents fluting damage).· Hybrid ceramic bearings (ceramic balls + steel rings) - high hardness and low friction.