Comp has several articles online of there process...

Depending on the speed and makeup of these nitrogen ions, some of them penetrate as far as .010-inches deep into the cam, while others bond themselves into the surface strata. The process creates three separate layers during the process. The deep layer, which provides strength against metal fatigue, is called the diffusion zone. A middle layer, called the compound zone, guards against abrasion and increases strength, while the surface layer affects the initial wear-in behavior of the cam, and gains lubricity from the nitriding process.