Phosphorus in the composite nitrided layers

Structure and properties of composite diffusive layers with ceramic precipi tates are considered. They are prepared on the base of carburized and nitri ded diffusive layers with precipitates of fine particles, e.g. oxides, sulp hides or phosphides. In this work composite diffusive layers with ceramic a ddition are considered on the example of diffusive nitrided layer with part icles of iron phosphide. Layers were generated in the process of nitriding in the atmosphere of partly dissociated ammonia with a slight admixture of gaseous phosphorus. As a result of the process a nitrided layer with the pr ecipitates of t iron phosphides is formed. The addition of small quantities of gaseous phosphorus to the nitriding atmosphere influences the structure and the properties of the nitrided layer. The diffusion layers were invest igated by means of the methods, a metallographic, an X-ray structural analy sis, microanalysis, and measurement of Vickers hardness as well as measurem ents of resistance to wear by Falex method. Description of the structure of the layers has been presented. They contain a zone of phosphides Fe3P and Fe2P, a zone of the nitrides Fe2-3N, and Fe4N, and a zone of precipitates o f iron phosphide Fe3P in the nitrides. Relations between chemical contents of the atmosphere as well as parameters of the process and structure and pr operties of layers have been defined. Iron phosphides addition in diffusive nitrided layer increases their hardness and their wear resistance. (C) 200 1 Elsevier Science B.V. All rights reserved.