Adhesive and Frictional Properties of Solid Lubricants for Powder Metallurgy Evaluated by Surface Force Apparatus.

Iron-based powder mixtures for the powder metallurgy process commonly contain solid lubricants. Both zinc stearate (ZnSt) and N,N'-ethylenebis(stearamide) (EBS), which are conventional lubricants in this field, exhibit similarly adequate lubrication performance. However, their effects on powder mixture flowability are different; that is, powder mixtures containing ZnSt exhibit better flowability than ones containing EBS. In this study, the adhesive and frictional properties of five surface combinations (iron-iron, iron-EBS, iron-ZnSt, EBS-EBS, and ZnSt-ZnSt) were investigated using surface force and resonance shear measurements. The adhesive forces obtained for all combinations were almost the same. On the other hand, the frictional forces for the iron-EBS and EBS-EBS combinations obtained from resonance shear measurement were larger than the others under low applied loads (<ca. 1.0 mN). This result suggests that the frictional properties of lubricants under low applied loads determine the powder mixture flowability. [ABSTRACT FROM AUTHOR]