Little spinners teeth at the last event were case hardened P20.. when they hit satanix they dug about 5mm into the mild steel then snaped there own titanium bar/disc... the p20 didnt even scuff.
I can see what your saying and I wouldn't expect the P20 to show any signs of damage against mild steel either. The reason being mild steel has a Brinell hardness of about 120 with sod all alloys but Hardox will have a minimum of 400 Brinell with lots of alloys and is designed to be wear and impact resistant so the results could be different.

I was only suggesting that hard edges could chip and therefore lose the nitrided layer and expose the softer material underneath.

I am actually quite intrigued to find out what the effects would be and how nitrided P20 would stand up.

My interest comes from the fact that I do heat treatment for a living, in fact I work here http://ht.bodycote.com/?OB=81&POB=276&ID=352


Ian