Modern Day-
During the industrial revolution and after, developments were made to the steel, with different chemical compositions added that created knives that were that were resistant to corrosion, easier to sharpen and stayed sharp longer.
Chemical compositions such as chromium are added for corrosion resistance, producing “stainless steels” such as 440C and AUS-8. Molybdenum content can be increased for more toughness such as in ATS-34 and 154CM. Cobalt increases strength and hardness, and Vanadium increases toughness and improves corrosion resistance. Higher amounts are found in VG10.
Heat treatment and cooling processes also varied, creating a wide variety of knives available today.
(Re-produced under fair-use and with credit)