A. Ingalls-Cruz, J. B. Hernández-Morales, J. A. Barrera-Godínez, B. F. Campillo-Illanes, Universidad Nacional Autónoma de México, México D.F., Mexico

Summary: Cryogenic treatment has been applied to tool steel parts for several years, however scarce fundamental knowledge is available for designing purposes. Also, the presence of eta-carbides in the final microstructure of heat-treated tool steels has been recognized as responsible for longer service time, particularly for those parts subjected to severe wear conditions. In this work, the precipitation path has been characterized. As received, quenched, criogenically treated and tempered samples were prepared and studied by optical, scanning and transmission microscopy. The influence of the cooling rate and time spent at the criogenic temperature (-196ºC) on the characteristics of the precipitates was established. With this information the precipitation path was established.