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 th ese materials has involved unlubricated experiments or tests in other than ambient air environments. If the suitability of amorphous metals is to be e valuated for engineering applications, a great deal more research is needed to assess their behavior under liquid lubricated conditions. Studies in th e 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 perfor med both dry and with diesel oil lubrication. The disks were composed of po lished SAE 52 100 steel, and pin specimens of type 303 stainless steel, com mercially-pure nickel (Ni-200), and an amorphous alloy of Zr-Cu-Ni-Ti-Al we re used. The amorphous alloy was the hardest of the three pin materials. Fr iction coefficients and wear rates were measured under a limited set of con ditions. Under dry conditions, the amorphous metal alloy performed comparab ly or slightly better than the other two pin materials, but under lubricate d 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 th e compatibility of non-ferrous materials with current engine lubricants. Ob servations 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.