Wear Behavior of P/M High Nb Containing γ-TiAl Alloy in Different Environments

The wear behavior of Ti–45Al–7Nb–0.3W (at%) alloy prepared by powder metallurgy (P/M) has been investigated using pin-on-disk wear tests at the room temperature. The dry sliding wear tests were performed against on a zirconia disk in different environments, viz, argon, hydrogen in nitrogen mixture, air and oxygen. The worn surfaces of Ti–45Al–7Nb–0.3W pins and wear debris were examined by scanning electron microscope, X-ray diffractometer and X-ray photoelectron spectroscopy. It was found that the high Nb containing Ti–45Al–7Nb–0.3W alloy didn't exhibit better wear resistance in the presence of oxygen than commercial γ-TiAl (Ti–47Al–2Nb–2Cr–0.2W) alloy. The oxidation on the worn surface and spalling of oxides caused by the mechanical force during sliding were the main reason for the high wear losses in the air and oxygen. The zirconia disk underwent a phase transformation caused by the high contact temperature and stress during the sliding tests. The abrasive particles produced in the wear tests largely consisted of the zirconia particles in different environments, except in the pure oxygen. The hard zirconia debris was embedded into the friction layer on the worn surfaces of TiAl pins, which provided protection against wear to some extent. The main wear mechanisms of Ti–45Al–7Nb–0.3W alloy were abrasive wear of two-body and three-body, some delamination and plastic deformation.