  Coarse-grained, metallic materials undergo microstructure refinement during
tribological loading. This in turn results in changing tribological properties,
so understanding deformation under tribological load is mandatory when
designing tribological systems. Single-trace experiments were conducted to
understand the initiation of deformation mechanisms acting in various
tribological systems. The main scope of this work was to investigate the
influence of normal and friction forces as well as crystal orientations on the
dominating deformation mechanism in a face-centred cubic concentrated solid
solution. While varying the normal force is easily realised, varying friction
forces were achieved by using several counter body materials paired against
CoCrFeMnNi. The subsurface deformation layer was either mediated through
dislocation slip or twinning, depending on the grain orientation and on the
tribological system. A layer dominated by dislocation-based deformation is
characterised by lattice rotation, the formation of a dislocation trace line or
subgrain formation. Such behaviour is observed for tribological systems with a
low friction coefficient. For systems dominated by deformation twinning, three
types of twin appearance were observed: small twins interacting with the
surface, large twins and grains with two active twin systems. Two different
twinning mechanisms are discussed as responsible for these characteristics.
