“80CrV2 is the most forgiving and reliable steel if you want to make a blade that is very hard but also tough. The main job of Cr is to increase hardenability, but it also decrease the initial austenite grain size, while V prevents austenite grain growth during hardening. As a result, 80CrV2 has an exceptionally small prior austenite grain size; therefore, at high hardness levels, 80CrV2 often has better toughness than carbon steel, though the difference disappears at softer tempers.”
For example, 80CrV2 knife blades achieve sufficient toughness at a hardness of about 63 HRC, whereas carbon steel blades at this level are often too brittle for demanding tasks. Medieval European swords were spring tempered, having a hardness of about 50 HRC. At this lower hardness, 80CrV2 offers hardly any advantage over plain carbon steel.