Material transfer behaviour between a Ti6Al4V blade and an aluminium hexagonal boron nitride abradable coating during high-speed rubbing

Material transfer behaviour between a Ti6Al4V blade and an Al-hBN abradable coating during high-speed rubbing was investigated by a high-speed rubbing test rig built by our research group. The effects of single pass depth and linear speed were studied. The transfer mechanism was discussed on the basis of observations of the blade and coating surface and section morphologies as well as comparisons between section morphologies of the coating transfer layer and the original coating. Material transfer from the coating to the blade was significant under the condition of high linear speed and low single pass depth. The coating transfer layer adhered to the blade at low linear speeds, whereas it was melted and smeared on the blade at high linear speeds. With an increase of the linear speed at a constant single pass depth, the wear mechanism of the coating changed from cutting and micro-rupture to plastic flow and melting. The high frictional heat brought about by the high linear speed was found to be the requirement of coating transfer, and the low single pass depth was the key to accumulation of the transfer on the blade.