The material transfer on corundum and steel counterbodies has been investigated in fretting tests performed in ambient air of different relative humidities (RH) on TiN coated tool steel. The morphology of the transfer layers on corundum counterbodies affects the friction and wear behavior of TiN coated steel. At 10% RH, a high friction is noted when a compact transfer layer adheres onto the corundum counterbody. At 80% RH, a low friction corresponds to a loose and fragmented transfer layer. At medium humidity (50% RH), a high friction stage is noted when a compact transfer layer is formed, whereas a loose and fragmented transfer layer leads to a low friction stage. (c) 2005 Elsevier B.V. All rights reserved.