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Carbo-austempered steels with a nanobainitic microstructure in the case are established as an exciting alternative in applications demanding high stability and reliability against wear and fatigue. In this work, the effect of heat treatment conditions, i.e. austenitizing and isothermal transformation temperatures, on the wear behavior under rolling/sliding conditions of a carburized cast steel with a nanobainitic structure in the surface was examined. The results show that wear damage is mainly due to contact fatigue, with a small extent of oxidative wear, abrasion and adhesion. The results were compared with the conventional tempered martensite plus retained austenite microstructure obtained by means of carburizing followed by quenching and tempering. The nanobainitic microstructures show a better wear resistance than the quenched and tempered microstructures. Also, the specific wear rate in carbo-austempered steels was lower as the isothermal heat treatment temperature decreased. Results are explained in terms of the microstructural differences, hardening behavior and plasticity of the materials under study.

Las personas sordas colombianas, por el difícil acceso a servicios de educación y salud, presentan mayor riesgo en salud sexual. Es necesario describir lo que los jóvenes sordos piensan y conocen sobre sexualidad, para orientar programas educativos dirigidos a esta población en particular. Objetivo: Interpretar las percepciones relacionadas con sexualidad, reportadas por un grupo de jóvenes sordos de Medellín (Colombia), con el fin de aportar elementos claves para el diseño de futuros programas de formación para la sexualidad dirigidos a las personas sordas. Metodología: Estudio cualitativo etnográfico, con la aplicación de grupos de discusión como estrategia metodológica. Los grupos de discusión fueron filmados y un intérprete transcribió los diálogos. Se realizó análisis argumentativo del discurso resultante y se contrastó con cuestionarios diligenciados por los participantes y con la literatura disponible. Resultados: El aprendizaje de la sexualidad en los jóvenes sordos ocurrió a partir de la pornografía. Su discurso se enfocó hacia lo erótico. La confianza en la pareja fue determinante para el uso o no del condón. Hubo temor hacia la consulta médica, la cual se representa como un abuso sexual. Conclusión: La educación tradicional y la falta de comunicación intrafamiliar se suman a la discapacidad auditiva para volver aún más vulnerable a este grupo poblacional.

Carburizing implies the existence of a carbon gradient from the surface to the core of the steel, which in turn will affect both the critical temperature for austenite formation and the kinetics of the bainitic transformation during the austempering treatment. Therefore, for future development of carbo-austempered steels with nanobainitic microstructures in the case, it is key to understand the effect of such carbon gradient has on the final microstructure and the mechanical properties reached by the heat treatments used. This work was divided into two parts, firstly two alloys with similar carbon content to those at the surface and center of the carburized steel were used to establish the optimal heat treatment parameters and to study bainite transformation kinetics by high resolution dilatometry. In a second step, a carburized alloy is produced and subjected to the designed heat treatments, in order to evaluate the microstructure and mechanical properties developed. Results thus obtained are compared with those obtained in the same carburized alloy after following the most common quench and temper treatment.