On the tribological properties of extremely different wood materials

Three different woods (lignum vitae; black fiber palm; spruce) were investigated regarding their friction and wear properties under abrasion and sliding. For the abrasive wear against silicon carbide paper, the palm wood gave the lowest removal of material, especially under an orientation of the black fibers normal to the contact region (on R–T-plane in R-direction). At the same time, this material had the highest anisotropy. Slightly less abrasion resistant was lignum vitae, whereas spruce was most easily abraded. This can be considered as an indication that spruce can easily be machined. Under sliding conditions against smooth steel, a similar tendency, but at much lower wear rates compared to abrasion, was found. The relatively high coefficient of friction under dry sliding allows the use of these woods as friction materials, for example in brakes. Additional lubrication of the two best woods, lignum vitae and black fiber palm, by soaked sunflower oil brought the coefficient of friction to a much lower level, so that the use of these woods as bearing materials in various applications is promising.