Effects of grain refinement and strength on friction and damage
evolution under repeated sliding contact in nanostructured metals
T. Hanlona,b, A.H. Chokshia,1, M. Manoharanb, S. Suresha,*
aDepartment of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
bGE Global Research Center, Niskayuna, NY 12309, USA
Available online 2 August 2005
Abstract
The early stage sliding contact fatigue behavior of nanocrystalline materials, with average and total range of grain sizes well below
100 nm, was studied. The evolution of friction and damage during repeated sliding contact in the nanocrystalline metals and alloys was
systematically compared and contrasted with that in ultrafine-crystalline and microcrystalline materials so as to develop a broad perspective
on the effects of grain size on sliding contact fatigue. Some critical experiments were performed to separate the effects of material strength
and grain size on friction and damage evolution. Over the range of materials examined, strength rather than grain size appeared to dominate
the steady-state friction coefficient and damage accumulation, each diminishing with substantial increases in material strength.
q 2005 Elsevier Ltd. All rights reserved.
Keywords: Nanocrystalline; Ultra-fine-crystalline; Equal channel angular pressed
1. Introduction
The potential use of nanocrystalline (nc) materials in
load-bearing structural applications inevitably will depend
on their resistance to damage and failure under repeated
loading conditions. Currently, however, there is a relative
paucity of experimental data pertaining to these properties
within the nc grain size regime. In a companion paper [1],
we examine the mechanical fatigue characteristics of nc
metals and alloys in terms of grain size, load ratio as well as
relative propensity for crack initiation and crack propa-
gation. This study was initiated to probe the sliding contact
fatigue behavior of several nc (average grain size typically
smaller than 100 nm) and ultra-fine-c