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Abstract
The lubricating lifetime of thin films of a perfluoropolyether (PFPE) based on liexafluoropropene oxide in the presence of ion-implanted 440C stainless steel is presented. Stainless-steel discs, either unimplanted or implanted with N2, C, Ti, Ti + N2, or Ti + C, had a thin film of PFPE (60–400 Å) applied to them reproducibly (± 20%) and uniformly (± 15%) using a device developed for this study. The lifetimes of these films were quantified by measuring the number of sliding-wear cycles required to induce an increase in the friction coefficient from an initial value characteristic of the lubricated wear couple to a final, or failure value, characteristic of an unlubricated, unimplanted couple. The tests were performed in a dry nitrogen atmosphere (< 1 % RH) at room temperature using a 3 N normal load with a relative sliding speed of 0.05 ms−1. The lubricating lifetime of the 440C couple was increased by an order of magnitude by implanting the disc with Ti. Ranked from most to least effective, the implanted species were Ti, Ti + C, unimplanted, N2, C ≃ Ti + N2. The mechanism postulated to explain these results involves the formation of a passivating or reactive layer which inhibits or facilitates the production of active sites. The corresponding surface microstructures induced by ion implantation, obtained using X-ray diffraction and conversion electron Mössbauer spectroscopy, ranked from most to least effective in enhancing lubricant lifetime were amorphous Fe-Cr-Ti, amorphous Fe-Cr-Ti-C + TiC, unimplanted, ε-(Fe,Cr)xN, x = 2 or 3, and amorphous Fe-Cr-C ≃ amorphous Fe-Cr-Ti-N.
Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in Kissimmee, Florida, October 8–11, 1995
Notes
Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in Kissimmee, Florida, October 8–11, 1995