To enhance performance, various surface treatments are used:
Nitriding/Carbonitriding: Creates an extremely hard (up to 70 HRC), wear- and fatigue-resistant surface layer with minimal distortion. Excellent for gears and shafts.
Induction or Flame Hardening: Localized surface hardening to create a hard, wear-resistant case over a tough core. Used for bearing journals, crane wheels.
Phosphate or Black Oxide Coating: Provides mild corrosion resistance, reduces friction, and aids in oil retention.
Chrome Plating: For excellent wear and corrosion resistance on hydraulic rods and pistons.
Shot Peening: Induces compressive surface stresses, dramatically improving fatigue life. Critical for springs and highly stressed cyclic-load components.