Why there is Cobalt in VG-10

[Larrin]

So let me ask: people love M4, especially CPM M4, for hard use knives. CPM Rex 45 is basically CPM M4 + cobalt. Shouldn't that then make for an even tougher, easier to work with M4? Why doesn't anyone use Rex 45 for knives - availability?

Both my article and Crucible's datasheet for CPM Rex 45 show a decrease in toughness with a cobalt addition. So no, it wouldn't make a tougher, easier to work with M4. http://www.crucible.com/PDFs/DataSheets2010/ds45rev12010.pdf