bearing
WHY 440C STAINLESS steel?
Good corrosion resistance to water and many weak chemicals.
Corrosion resistance can be improved by passivation.
Good for temperatures up to 300°C.
Slightly softer than chrome steel so lower load ratings.
Will corrode in salt water or salt spray and poor resistance to acids/alkalis.
More expensive than chrome steel.
What is 440C?
A martensitic stainless steel. It's composed of these major alloy elements (I don't list the minor elements since they don't play a major role):
Carbon: 0.95-1.25% This increases hardenability and wear resistance but decreases toughness in higher amounts.
Manganese: 45% This is added to reduce brittleness and improve forgeability hardenability and reducing deformation.
Silicon: 30% This is a deoxidizer and improves hot-forming properties.
Chromium: 17.00-18.00% Added only to high alloy tool steels this improves hardenability high wear resistance toughness and corrosion resistance.
Molybdenum: 50% Improves deep hardening and toughness.
These basic elements (along with iron) are a simple combination that works well together and has for many decades.
This alloy is technically classified as UNS (Unified Numbering System) S44044. It's also classified as SAE (Society for Automotive Engineers) as 51440C.
The American Iron and Steel Institute classifies it as 440C martensitic standard stainless steel. Most modern knifemakers simply call it 440C.