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

摘要

Iron-based powder mixtures for the powder metallurgy (PM) 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 performances. However, their effects on the powder mixture flowability are different; that is, ZnSt causes better flow than EBS. In this study, the adhesive and frictional properties of the five surface combinations (Fe-Fe, Fe-EBS, Fe-ZnSt, EBS-EBS, and ZnSt-ZnSt) were investigated using surface forces and resonance shear measurement. The adhesion forces obtained for all combinations were almost the same. On the other hand, friction forces for Fe-EBS and EBS-EBS combinations, obtained from resonance shear measurement, were larger than others, especially at low applied load (< ca. 1.0 mN). This result suggests that the frictional properties of lubricants at low applied load determine the powder mixture flowabilities.