Optimizing Surface Activation for Repeatable White Layer Growth during Gas Nitriding

Surface activation improves the repeatability of gas nitriding carbon and alloy steels, but companies often struggle to identify the most effective activation parameters.  This study contains a brief review of the current guidelines and literature for surface activation prior to gas nitriding, and presents the experimental results of various activation techniques on the formation of white layer in the first stage of nitriding both for general alloy steels and for nitriding grades of steel.  Surface activation techniques to be presented include alkaline cleaning, acidic surface activation, and thermal oxidation at various temperatures. The thickness of the oxide layer which results from each activation process and the thickness and variation of white layer after the initial stage of nitriding will be discussed.  With these results, a repeatable procedure can be developed for optimal surface activation (in terms of time and processing costs) to prepare carbon and alloy steels for gas nitriding.