The effects of environment on the dry sliding wear of eutectic Fe30Ni20Mn35Al15

The wear of as-cast eutectic Fe30Ni20Mn35Al15, which consists of lamellar f.c.c. and B2 phases, was studied using pin-on-disk tribotests in four different environments: air, dry oxygen, dry argon, and a 4% hydrogen/nitrogen mixture. The counterface in all the tests was yttria-stabilized zirconia. Wear debris and wear tracks were examined in detail to investigate the surface effects during dry sliding and these were correlated with the wear properties. It was found that the wear rate was about 40% lower in tests performed under argon, compared to tests conducted in either air or oxygen. However, the wear rate was about 1000% higher when the tests were conducted in a hydrogen-containing environment. The near-surface regions of the pins were examined using transmission electron microscopy of cross-sectional specimens produced by focused ion beam milling. For tests in oxygen-containing environments, abrasive particles were produced by oxidation. These, protruded and peeled off from the matrix and mixed with the debris from the counterface, producing a combination of a two-body and three-body abrasive wear-controlled processes. In contrast, for tests under argon, plastic flow mechanisms dominated. The dramatic increase of wear in 4% hydrogen/nitrogen was due to hydrogen embrittlement, which meant that little plastic flow occurred, a feature consistent with the results of prior tensile tests.