With salt-bath nitriding for example, a wash system is needed to remove the residual salts left on the processed steel surface. The surface metallurgy is fixed based on the salt analysis by titration. Gas nitriding uses ammonia (2NH3), which under heat – and with the assistance of the processed steel acting as a catalyst – decomposes to: 2N + 3H2

This means that with a fixed gas chemistry the resulting surface metallurgy is fixed. The process of pulsed plasma nitriding relies on the ionization of nitrogen and hydrogen (particularly the nitrogen). The hydrogen has a twofold purpose. It is a dilutant gas as well as a cleaning (reducing) gas. Thus, the ratio of nitrogen to hydrogen can be varied according to the steel being treated and the immediate surface metallurgy requirements necessary for the specific application. Consequently, gas ratio variation equals variable surface metallurgy.