D2 is a high carbon high chromium steel, this gives it a very impressive wear resistance and toughness due to a large amount of carbide present in its structure. D2 shows minimal amounts of distortion in heat treating like other air hardening steels. It can also be machined when in an annealed condition. As a bonus polished D2, thanks to its chromium content shows a level of corrosion resistance.
D2 as its name would suggest is primarily used for the construction of tools such as dies in a forge, shear blades, thread rolling dies etc
AISI ASTM A681
BS EN ISO 4957