Which mechanism most enabled the widespread use of iron in ancient civilizations, overcoming its brittleness?

💡 Explanation

When iron is heated in the presence of nitrogen-rich materials, case hardening (nitriding) occurs because nitrogen diffuses into the surface, forming hard iron nitrides that increase wear resistance, allowing iron to be used for tools and weapons despite its inherent brittleness. Therefore, case hardening results, rather than quenching, smelting or alloying, which address other material properties.

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