Phosphorus in the composite nitrided layers

Structure and properties of composite diffusive layers with ceramic precipitates are considered. They are prepared on the base of carburized and nitrided diffusive layers with precipitates of fine particles, e.g. oxides, sulphides or phosphides. In this work composite diffusive layers with ceramic addition are considered on the example of diffusive nitrided layer with particles 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 precipitates 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 investigated by means of the methods, a metallographic, an X-ray structural analysis, microanalysis, and measurement of Vickers hardness as well as measurements 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 of iron phosphide Fe3P in the nitrides. Relations between chemical contents of the atmosphere as well as parameters of the process and structure and properties of layers have been defined. Iron phosphides addition in diffusive nitrided layer increases their hardness and their wear resistance.