Modification of composite nitrided layers by phosphorus compounds

Abstract

Composite diffusive nitrided layers with precipitates of iron phosphides are considered. They are generated in the process of nitriding in an atmosphere of partly dissociated ammonia with a slight admixture of gaseous phosphorus. The addition of small quantities of gaseous phosphorus to the nitriding atmosphere influences the structure and properties of the nitrided layer. The layers consists of: a zone of phosphides of Fe3P and Fe2P, a zone of nitrides of Fe2–3N and Fe4N, and a zone of precipitates of iron phosphide Fe3P in the zone of nitrides of Fe2–3N and Fe4N. The relations between chemical contents of the atmosphere, as well as the parameters of the process, structure and properties of the layer, have been defined. Iron phosphide reinforcement in the diffusive nitrided layer increases its hardness and resistance to wear.