Wear Resistance under Non-Lubricated Condition of Nb-Containing TWIP Steel
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Wear Resistance under Non-Lubricated Condition of Nb-Containing TWIP Steel V.H. Mercado1, I. Mejía1, Y. Salinas-Escutia1, A. Bedolla-Jacuinde1. 1
Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U-5”, Ciudad Universitaria, 58066 Morelia, Michoacán, México. E-mail: [email protected], [email protected]
ABSTRACT
Twinning induced plasticity (TWIP) steels are one of the most attractive advanced highstrength steels for structural applications due to their unique combination of strength and ductility, which is associated with so-called “mechanical twinning”, where twins act as strong obstacles to the dislocation motion. In this context, Nb addition to TWIP steel increases the strength and refines grain size by nanoscale NbC precipitates. Nowadays, highmanganese TWIP steels are extensively studied. However, information in the specialized literature about their tribological properties is limited. This research work studies the wear behavior of high-manganese austenitic Fe–20Mn–1.5Si–1.5Al–0.4C TWIP steel microalloyed with Nb. The wear behavior was evaluated under non-lubricated sliding condition using the “pin-on-ring” technique. As-solution heat treated samples were worn under loads of 53, 104 and 154 N, and at sliding speeds of 0.22, 0.60 and 0.87 m/s. The wear resistance was evaluated in terms of the loss weight. Wear debris and worn surfaces were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). In general, results show that the wear resistance significantly improves as the sliding speed increases. On the other hand, Nb addition to present TWIP steel produces a slight increase of the wear resistance. Also, it was found that the oxide layer plays a significant role in the wear resistance behavior of this kind of steel. Key Words: steel, tribology, Nb,
INTRODUCTION Recently, a new generation of steels with high properties of strength and ductility is developed; they are so-called twinning induced plasticity (TWIP) steels [1]. TWIP steels are being used in the automotive industry in order to increase the safety of passengers [2]. It is well-known that TWIP steels have excellent properties of absorption energy on impact, which is perfect for structural applications on cars [3]. The high combination of strength and ductility in this kind of steels is attributed to the “twinning” deformation mechanism, where twins act as obstacles for the dislocation movement in a sort of “Hall-Petch effect” [4-5]. On the other hand, new research work on TWIP steels are focused on increasing their mechanical properties by different ways such as phase transformation, precipitation hardening, grain refinement and microalloying elements. It
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