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A two-phase submicron microstructure is produced when mixing BAM with titanium diboride
Reducing wear and friction remains a constant goal to improve the efficiency, decrease energy costs and extend the life of machinery. Both liquid and solid lubricants play an important role in providing antiwear and lubricity characteristics to achieve these results.
One solid coating that has gained more attention recently is an alloy of boronaluminum-magnesium (AlMgB^sub 14^, nicknamed BAM) prepared initially with addition of silicon and more recently titanium diboride. BAM was found to exhibit exceptionally strong hardness in 1999 by researchers at the U.S. Department of Energy's Ames Laboratory.
Alan Russell, professor of Material Science and Engineering at Iowa State University, in Ames, Iowa, says, "BAM by itself displays a hardness between 30 and 32 gigapascals. Titanium diboride also has a similar value, but when we combine the two materials a synergy develops that leads to an improvement in hardness."
Russell adds, "Mixing BAM with titanium diboride produces a two-phase submicron microstructure that leads to an increase in hardness that ranges between the mid-30s and low-40s gigapascals, depending on the ratio of the two components."
Project leader Bruce Cook and Russell believe that BAM and titanium diboride generate a strong bonded interface between the two materials. This interface inhibits crack formation.
The coefficient of friction for the BAM-titanium diboride alloy ranges between 0.02 and 0.10, according to Russell. He adds, "The high boron content contributes to the low coefficient of friction. In contrast, polytetrafluoroethylene exhibits a coefficient...