440C vs 440B Stainless Steel: High-Hardness Martensitic Alloys

 

How do their compositions differ?​

440B has 16-18% chromium, 0.75-0.95% carbon, and 0.4-0.6% molybdenum. 440C increases carbon to 0.95-1.20% and molybdenum to 0.4-0.7%, enhancing hardness and wear resistance.​

 

Which offers better hardness and wear resistance?​

440C reaches 58-60 HRC after heat treatment, harder than 440B's 58-60 HRC (slightly lower upper limit). It has excellent wear resistance, making it suitable for high-performance bearings and cutting tools.​

 

How do they compare in corrosion resistance?​

Both offer moderate corrosion resistance in dry environments, with similar performance due to their chromium content. They can rust in moist or salty conditions, with no significant difference between the two.​

 

What about their fabrication properties?​

440B is slightly easier to machine and form than 440C due to its lower carbon content. Both require careful heat treatment to achieve full hardness without brittleness, with 440C needing more precise temperature control.​

 

Where are 440C and 440B commonly used?​

440B is used in high-performance knife blades, precision bearings, and valve parts. 440C finds applications in high-speed bearings, cutting tools, and parts needing maximum wear resistance.