Friction and wear performance of ion-beam-deposited diamond-like carbon films on steel substrates
Abstract
In this study, we investigated the friction and wear performance of ion-beam-deposited diamond-like carbon (DLC) films (1.5 μm thick) on AISI 440C steel substrates. Furthermore, we performed a series of long-duration wear tests under 5, 10 and 20 N loads to assess the load-bearing capacity and durability limits of these films under each load. Tests were performed on a ball-on-disk machine in open air at room temperature, about 22 ± 1 °C, and humidity, about 30% ± 5%. For the test conditions explored, we found that (1) the steady state friction coefficients of pairs without a DLC film were in the range 0.7-0.9 and the average wear rates of 440C balls (9.55 mm in diameter) sliding against uncoated 440C disks were on the order of 10 -5 mm 3 N -1 m -1, depending on contact load; (2) DLC films reduced the steady state friction coefficients of test pairs by factors of 6-8, and the wear rates of pins by factors of 500-2000; (3) the wear of disks coated with a DLC film was virtually unmeasurable whereas the wear of uncoated disks was quite substantial; (4) the DLC films were able to endure the range of loads, 5-20 N, without delamination, and to last over 1 000 000 cycles before wearing out. During long-duration wear tests, the friction coefficients were initially on the order of 0.15, but decreased to some low values of 0.05-0.07 after sliding for 15-25 km, depending on the load, and remained low until wearing out. This low friction regime was correlated with the formation of a carbon-rich transfer film on the wear scar of 440C balls. Microlaser Raman spectroscopy and scanning electron microscopy were used to examine the structure and chemistry of worn surfaces and to elucidate the wear- and friction-reducing mechanisms of the DLC film.
- Publication:
-
Diamond and Related Materials
- Pub Date:
- 1994
- DOI:
- 10.1016/0925-9635(94)90042-6
- Bibcode:
- 1994DRM.....3..119E