Subsurface Microstructural Evolution during Scratch Testing on Bcc Iron

Dominic Linsler,Christian Greiner,Friederike Ruebeling

doi:10.3390/met11081258

Abstract

Subsurface microstructures influence the friction and wear behavior of metallic tribological systems, among other factors. To gain a basic understanding of the microstructural changes occurring during sliding processes, face-centered cubic model systems, for example a copper system with a sapphire sphere sliding against it, were previously characterized. Such systems showed the evolution of the dislocation self-organization phenomenon called the dislocation trace line. To test the occurrence of this dislocation arrangement in bcc metals, in this study a ruby ball was slid against electropolished bcc iron under an increasing normal load. The wear track topography and subsurface microstructure were characterized using white light interferometry and scanning transmission electron microscopy. The analysis suggested that at least for bcc iron, the evolution of a dislocation trace line is connected with the onset of pronounced plastic deformation.

Highlights

Subsurface plastic deformation is inherently connected to the tribological behavior of many metallic tribological systems in all wear regimes—it has been observed in ultra-low wear regimes with wear coefficients of 10−10 mm3 /(N m) [1,2,3,4,5], in lubricated systems in mild wear regimes [6,7], and in dry sliding systems [8,9,10]
The analysis suggested that at least for bcc iron, the evolution of a dislocation trace line is connected with the onset of pronounced plastic deformation
A certain amount of plastic deformation was a necessary condition for the formation of the dislocation trace line

Summary

Introduction

Subsurface plastic deformation is inherently connected to the tribological behavior of many metallic tribological systems in all wear regimes—it has been observed in ultra-low wear regimes with wear coefficients of 10−10 mm3 /(N m) [1,2,3,4,5], in lubricated systems in mild wear regimes [6,7], and in dry sliding systems [8,9,10]. Subsurface plastic deformation is visible in severe wear regimes with wear coefficients of 70 mm3 /(N m). The friction force significantly influences the subsurface plastic deformation and wear particle formation [11,12], influencing the wear behavior. Cutting processes as an example of extreme wear induce plastic deformation below the finished surface in addition to material removal. This holds true for cutting with geometrically defined [1,13]. Beckmann et al [18]

Methods

Discussion

Conclusion