Carbonitriding is a case hardening process by which carbon and alloy steels are held at an elevated temperature (usually above the transformation range) in a gaseous atmosphere from which they absorb carbon and nitrogen simultaneously, and are then cooled to room temperature at a rate that will produce desired case and core properties. The carbon is derived from any carbon rich gas or vapourised liquid hydrocarbon that is suitable for carburising. Ammonia is the source of nitrogen.
Carbonitriding thus is a modified gas carburising process, rather than a form of nitriding. The modification consists of introducing ammonia into the gas carburising atmosphere in order to add nitrogen to the carburised case as it is being produced.
Advantages
Although carbonitriding is a modified carburising process, its applications are more restricted than those of carburising. It is largely limited to case depths of about 0.75 mm or less, whereas no such limitation exists for carburising. However, the resistance of a carbonitrided surface to softening during tempering is markedly superior to that of a carburised surface. Other notable differences exist in terms of residual stress pattern, metallurgical structure, fatigue and impact strength at specific hardness levels and effect of alloy composition on case core characteristics.
Gas carbonitriding is carried out in our fluidised bed furnace (2 units), continuous and Lindberg sealed quench furnaces.
