D2 Tool Steel for Knife Blades
AISI D2 Tool Steel
Manufacturer: Various (CPM-D2 only by Crucible)
D2 is one of the higher performing steels available for knifemaking, but since it is a tool steel it is more susceptible to corrosion. Its somewhat high Chronomium content gives it slightly better corrosion resistance than most tool steels earning it the distinction of being a semi-stainless.
The steel is a favourite among knife collectors, applauded for it's good wear resistance, and strength, while offering some resistance to corrosion. D2 does make a great knife material and can be hardened to RC60-62 safely. It does not, however, polish up very well at all and is very difficult to put a nice finish on. It is also more difficult to sharpen than 154CM or 440C, but will hold an edge longer. D2 has a fairly coarse grain structure so it will not take as fine an edge and is more suited to obtuse angles for the secondary bevel when sharpening.
CPM-D2 is an experimental steel that Crucible made one batch of. It has been used by a lot of production knife companies such as Spyderco and Kershaw and has exactly the same as their standard D2, except that it is produced using their Particle Metallurgy process. According to Crucible:
"The CPM process should improve the toughness, improve the machinability and grindability, improve the finish and may even help improve the stain or corrosion resistance."