440C vs 420 Stainless Steel: High-Hardness Martensitic Alloys

 

How do their chemical compositions differ?​

420 contains 12-14% chromium, 0.15-0.4% carbon, and no molybdenum. 440C has 16-18% chromium, 0.95-1.20% carbon, and 0.4-0.7% molybdenum,

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, significantly harder than 420's 50-55 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?​

440C offers better corrosion resistance than 420 due to its higher chromium content, resisting rust better in moist environments. Both handle dry settings well, but 440C holds up longer in mild humidity and mild chemical exposure.​

 

What about their fabrication properties?​

420 is more formable in its annealed state, easier to bend and shape. 440C is harder to machine and requires more precise heat treatment to avoid brittleness, but it holds a sharper edge after heat treatment.​

 

Where are 440C and 420 commonly used?​

420 is in surgical tools, valve parts, and low-cost knife blades. 440C finds applications in high-speed bearings, cutting tools, and industrial blades needing maximum wear resistance.