Modification of composite nitrided layers by phosphorus compounds

Composite diffusive nitrided layers with precipitates of iron phosphides ar e considered. They are generated in the process of nitriding in an atmosphe re of partly dissociated ammonia with a slight admixture of gaseous phospho rus. The addition of small quantities of gaseous phosphorus to the nitridin g 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 n itrides of Fe2-3N and Fe4N, and a zone of precipitates of iron phosphide Fe 3P in the zone of nitrides of Fe2-3N and Fe4N. The relations between chemic al contents of the atmosphere, as well as the parameters of the process, st ructure and properties of the layer, have been defined. Iron phosphide rein forcement in the diffusive nitrided layer increases its hardness and resist ance to wear. (C) 2000 Elsevier Science S.A. All rights reserved.