Using nitrogen in the formation of the hard case overcomes the problems associated with case carburizing including depletion of matrix chromium and carbon with accompanying lower hardness and corrosion resistance.

Case hardening is a thermochemical heat treatment transferring carbon from a carburizing atmosphere into the surface of a low-carbon, low-alloy steel, austenitized at a temperature of, for example, 950 C (1740 F), which upon quenching, leads to a hard martensitic case surrounding a softer core. Without the high load-bearing capacity and the compressive residual stresses of the case, gears in motor vehicles would have a reduced service life, and so would have many other machine parts without case hardening.