In an attempt to better understand the mechanisms of material transfer and adhesion to coated surfaces, magnetron sputtered TiB 2 coatings on M2 tool steel discs have been tested against commercially pure Al, Cu and Ti pins using an environmentally controlled vacuum pin-on-disc tribometer. A constant load of 4.9 N and three different sliding speeds of 0.015, 0.120 and 0.650 m/s were employed. Pin-on-disc tests were done in ambient air and under argon atmosphere. Material transfer to the TiB 2 surface was observed to occur in two different morphologies including the formation of a thin layer of metal covering the counterface (smearing), and material transfer in the form of larger pieces, which normally became adhered to the counterface. The minimum amount of material transfer was from the Cu pin to the TiB 2 coating surface in both argon and ambient air tests. For Al and Ti, the amount of material adhered to the coating surface was significantly greater in argon than in ambient air tests. The most severe form of adhesion occurred when the Ti pin was tested against the TiB 2 coating in the argon atmosphere. For Al, the transfer material mostly smeared on the TiB 2 surface in argon. More material was removed from the metal pins in ambient air and the transferred material became mostly oxidized loose wear debris during sliding. The relative amounts of the debris formed could be ranked with respect to the driving forces of the metals for oxidation (i.e. standard Gibbs free energy of oxide formation); it was highest for Al and lowest for Cu. Sliding speed affected both the amount and morphology of the material transferred onto the TiB 2 coating surface. For Ti, the amount of material adhered to the TiB 2 coating surface increased with sliding speed in both argon and ambient air. The adhered particles were mostly in the form of chunks of material at the high sliding speed. The observations reported here showed the importance of test atmosphere, loading conditions, and the mechanical properties of the metals on the adhesion and transfer behavior of metals on coating surfaces.