Here's a 2003 BladeForums post by Sal Glesser about H-1, which is Spyderco's nitrogenated steel where he mentions that X-15 and INFI include nitrogen. Also, here are a couple of pages that discuss the effects of elements added to knife steel:

Spydeco EDGE-U-CATION: Steel Element Information and
Swiss Army Knife Mall: Knife Steel.

There are no shortage of other references, and I'm sure that many are better. The main reason I included the Swiss Army Knife Mall page was that it stresses heat treatment as the #1 factor in blade performance, and that's where Bussekin knives excel. Now refer to Busse Combat's INFI information page. As noted at the bottom, INFI was not developed as a stainless steel, but it has strong corrosion resistance, probably in large part to the nitrogen. Though in the final analysis, INFI's legendary performance, along with that of SR101 and SR77, owe more to their heat treatment and quality control than to their steel formulation.