Friction and wear of a Zr-based amorphous metal alloy under dry and lubricated conditions

The unusual internal structure of amorphous metals has been of interest to the tribology community for several decades, but most of the research on these materials has involved unlubricated experiments or tests in other than ambient air environments. If the suitability of amorphous metals is to be evaluated for engineering applications, a great deal more research is needed to assess their behavior under liquid lubricated conditions. Studies in the early 1980s focused on Fe-Co-B-Si compositions. The results reported here focus on an alloy system based on zirconium. Pin-on-disk tests were performed both dry and with diesel oil lubrication. The disks were composed of polished SAE 52 100 steel, and pin specimens of type 303 stainless steel, commercially-pure nickel (Ni-200), and an amorphous alloy of Zr-Cu-Ni-Ti-Al were used. The amorphous alloy was the hardest of the three pin materials. Friction coefficients and wear rates were measured under a limited set of conditions. Under dry conditions, the amorphous metal alloy performed comparably or slightly better than the other two pin materials, but under lubricated conditions, it had the highest friction coefficient and highest wear rate of the three combinations. Differences in the ratios of dry to lubricated wear rates for the three material combinations are discussed in terms of the compatibility of non-ferrous materials with current engine lubricants. Observations on the nature of amorphous alloy wear particles are linked to a combination of simultaneously occurring wear processes. No sliding-induced transformations were detected by X-ray methods. (C) 2001 Elsevier Science B.V. All rights reserved.