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

 

How do their compositions differ?

440B contains 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%, which enhances its ability to achieve high hardness after heat treatment.

 

Which offers better hardness and wear resistance?

After heat treatment, 440C reaches 58-60 HRC, harder than 440B's 56-58 HRC. This makes 440C more wear-resistant, suitable for high-performance bearings and cutting tools that need to maintain sharp edges.

 

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 in resistance 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 (quenching and tempering) to achieve full hardness without becoming overly brittle.

 

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, such as industrial blades.