The effect of tribolayers on the behavior friction of X40CrMoV5/Fe360B steel couple in an open sliding contact
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C. Richard Université François Rabelais de Tours (UFRT), Laboratoire de Mécanique et Rhéologie (LMR) EA 2640, Tours 37200, France (Received 7 November 2016; accepted 16 February 2017)
Metal working tools are generally exposed to hard conditions, and the control of their excessive wear is of a crucial importance for the metal working process. Indeed, tribo-layers as mechanically mixed layers and wear debris are completely involved in the wear behavior. This paper undertakes the study of the frictional behavior and wear of X40CrMoV5 (AISI H13) tool steel as a function of speed rotation at room temperature. The utmost objective of this research work is to assess some wear mechanisms of this tool steel used at room temperature. The tribological experiments were accomplished on high temperature pin-on-disc tribometer with an open sliding contact. The pin material was X40CrMoV5 steel and the disc material was Fe360B steel. The investigations were accomplished for different rotatory speeds of the disc ranging from 25 rpm to 100 rpm, and different nominal pressure. SEM and EDS explored the development surface damage and oxides tribo-layers. It was concluded that the increase of the rotation speed of the disc and the nominal pressure reduce the friction coefficient by the creation of a wear protective layer.
I. INTRODUCTION
Since steel working tools face high thermal and mechanical pressure, they are always damaged, which leads to the liberation of some debris. Particles in a loose or compacted form gathered between the contacting surfaces can also happen during the sliding process.1 The origin of this wear fragments can be the external contamination to the augmentation of wear fragments. This kind of particles in a tribo-system has been mentioned as “third body” or “tribo-particulate”.2–4 Therefore, wear fragments particles are deeply included in the wear processes.5 Generally, a tribo-layer is formed on worn surfaces. In the most cases, the tribo-layer is considered to be a mechanically mixed layer (MML), which is comprised of materials from both the sliding counterparts.6,7 Thus, the formation of tribolayers is an expected phenomenon during the sliding of metals. Certainly, tribo-oxides appear in air. Hence, the tribolayers are generally referred to as tribo-oxide layers.8–11 In fact, transitions in wear with sliding time are basically caused by the improvement of wear-protective layers coming after the compaction of wear fragments particles on the rubbing surfaces. The conformity of the tribo-particulates to each other and to the contacting Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.81
surfaces plays an efficient role in the quick decline in the value of the friction coefficient. Moreover, friction or externally applied parameters promote the oxidation of the contacting metal or alloy surfaces. Consequently, wear processes can get modified because they are related to the change from metallic fragments to oxide fragments. An adv
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