Wear particles, surfaces and plastic flow generation in unimplanted and Mo ion implanted carbon steel under friction E.V. Legostaeva * , Yu.P. Sharkeev Institute of Strength Physics and Materials Science, SB, RAS, 2/1 Akademcheskii pr., Tomsk 634021, Russian Federation Available online 14 June 2005 Abstract The purpose of the present work is to study the influence of the structure modified by ion implantation on mechanisms for wear particles, surfaces and plastic flow generation. The ‘block-on-shaft’ testing procedure was used to investigate the wear behavior of the ferritic/pearlitic carbon steel (in 0.45 wt% C) in the unimplanted and Mo ion implanted states. New approach to description of plastic deformation and destruction under friction is introduced on the basis of concepts of structural levels of plastic deformation and physical mesomechanics. In order to investigate the plastic flow behavior under friction, a unique method was applied using the optical TV-complex ‘TOMSC’. Reconstruction step-by-step of the displacement vector fields helps to reveal different plastic deformation stages evolving from fragmented mesostructure to large vortex mesostructure. It has been found that the character of plastic flow in the subsurface layers during friction determines the mechanism for generation and separation of the wear particles and formation of the wear surfaces. It was concluded that the formation of the modified structural-phase state in the surface layer of the Mo ion implanted specimens prevents the fragmented structure formation at mesolevel and retards the mesofragment vortex movement in the subsurface layer, thereby decreasing the intensity of the wear particles generation and finally increasing wear resistance. q 2005 Elsevier Ltd. All rights reserved. Keywords: Wear particles; Plastic flow; Microstructure; Deformation scale levels; Ion implantation 1. Introduction One of the most important problems of the friction physics is plastic flow, surface topography and wear particles in tribocontacts of sliding parts. The analysis of wear particles and surface topography can be used to identify the wear mechanisms in the surface layers during friction [1–3]. There are a lot of experimental data illustrating wear mechanisms changes and wear resistance improvement due to some surface modification methods, such as particle beams and plasma flow treatments [4–8]. It is well known, that high dose ion implantation gives rise to a considerable modification of the microstructure, thereby decreasing wear of the near-surface layers [6–10]. However, there are no clear concepts, which can explain the changes of the wear mechanisms after ion implantation. The purpose of the present work is to study the influence of the structure modified by ion implantation on mechan- isms of wear particles, surfaces and plastic flow generation. A new approach to the description of plastic deformation and destruction under friction is introduced on the basis of concepts of structural levels of plastic deformation and physical mesomechanics. Physical mesomechanics describes a loaded solid as a hierarchic system in which the deformation and destruction processes at micro-, meso- and macroscale levels are self- consistent [11–13]. Plastic deformation of a loaded solid at the microlevel is realized by the generation and motion of dislocations forming the dislocation substructures [14,15]. Transmission electron microscopy is one of the principle methods of investigation of plastic deformation at the microlevel. During deformation the dislocation density increases and when a particular critical density is reached, the local structural transformations takes place over a large distance forming the fragmented structure [16]. A new type of three dimensional volume carrier of plastic deformation appears at this scale level. Plastic flow at this scale occurs following the ‘shear and rotation’ scheme and is classified as the mesolevel in [11]. To make the direct visualization of Tribology International 39 (2006) 417–425 www.elsevier.com/locate/triboint 0301-679X/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.triboint.2005.04.022 * Corresponding author. Tel.: C7 3822 286911; fax: C7 3822 492576. E-mail address: lego@ispms.tsc.ru (E.V. Legostaeva).