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The effect that Cr, Mo and Cu exert on the behavior of TWIP steels (Fe-C-Mn-Al-Si) with high Mn content was evaluated. The proposed TWIP steel is with 20% Mn. On the other hand, currently within mining processes there are different devices that are specifically exposed to wear in the crushing process, the steel that is currently used is Hadfield steel with percentages of 10 to 14% of Mn, another aspect was to compare the mechanical properties of the TWIP steels manufactured in this project with the Hadfield steels that are currently used. Se evaluó el efecto que el Cr, Mo y Cu ejercen sobre el comportamiento de los aceros TWIP (Fe-C-Mn-Al-Si) con alto contenido de Mn. El acero TWIP propuesto es con 20% de Mn. Por otra parte en la actualidad dentro de los procesos mineros hay diferentes dispositivos que están expuestos al desgaste específicamente en el proceso de trituración, el acero que actualmente se utiliza es el acero Hadfield con porcentajes de 10 a 14% de Mn, otro de los aspectos fue comparar las propiedades mecánicas de los aceros TWIP fabricados en este proyecto con los aceros Hadfield que actualmente se emplean.

Austenitic manganese steels are widely used in mineral comminution processes due to their good wear resistance and high toughness. The classical chemical composition for austenitic manganese steel in these applications is about 12%Mn and 1.2%C, steel first produced by R. Hadfield more than a century ago. Ever since, many efforts to improve its mechanical properties and wear resistance have been made, mostly driven by the continuous demand of the mining industry for bigger crushing equipment and lower production costs. In this work, two types of austenitic manganese steels containing a relative high content of carbon are investigated. The high carbon content provided the steels good wear resistance, but compromises their mechanical properties. An important deleterious effect observed due to high carbon content was embrittlement due to the precipitation of carbides at grain boundary. Another important feature of the steels under study was their difference in manganese content, which played an important role in stabilizing carbon in the austenitic matrix. Furthermore, both steels contained titanium, which contributed to increase wear resistance through the formation of a hard phase of stable carbides. Heat treatments were performed, aimed to solubilize precipitated carbides and to improve quenching conditions, in order to avoid reprecipitation of these carbides, especially in thick castings. The results presented showed a correct selection of the temperature for austenitization and, additionally, a characterization of the kinetics of the re-precipitation phenomenon. After the improvements of the microstructure, the steels were tested in pilot scale crushers to assess their wear properties. Additionally, field tests were performed as well in industrial applications: in a cone crusher, a horizontal shaft impactor and a hammermill. The results of the metallurgical and tribological studies demonstrated the need for improvements in the chemical composition of the steels. For this reason, different elements, such as Nb, Al, Ni, Mo, were added to the composition of the steels. Finally, a cost estimation of the industrial production of these new steels was performed, in order to assess their economic feasibility. The results showed that the phenomenon of carbide re-precipitation is the main reason for embrittlement. Manganese content was the most important variable to stabilize the microstructure. The addition of Ni to this steel resulted in an improvement of mechanical properties, while maintaining the good wear resistance. Two appendixes are included with original research work that was secondary to the scope of the thesis project. The first, presents a mathematical model that simulates the granulometric curve of the product from a crusher, but taking in consideration the wear in the liners of the machine. The other, presents an ultrasound treatment, which had comminution effects in different types of mineral particles. Ultrasound was tested as well in a leaching process to investigate their kinetic enhancement effects.

International audience; Austenitic manganese steels with 12% Mn and 1.2% C, known as Hadfield steels, are of great interest owing to their good mechanical properties, especially their high strengthening ratio during plastic deformation. For many applications only a limited thickness of the surface layer is submitted to wear and therefore manufacturing of coatings with the appropriate Fe---Mn---C composition appears an attractive solution. The present work deals with the production, by laser cladding, of Hadfield coatings on a low carbon steel. Sound austenitic layers are achieved with a thickness in the range 0.5 – 1 mm. During cold working, a large Vickers hardness increase is observed (from about 200 to 650 HV). Formation of a texture is accompanied by a γ → α transformation of the fine and dendritic microstructure of the Hadfield coating.