Contribution of crystallographic texturing to the sliding friction behaviour of fcc and hcp metals

摘要

Dry sliding wear tests were performed on two polycrystalline materials representing fcc and hcp crystal structures, i.e. aluminum and titanium, respectively. A block-on-ring type wear machine with a rotating ring made of AISI 52100 type bearing steel was used and variation of coefficients of friction with sliding distance was measured at a sliding speed of 0.13 m s~(-1) and normal load of 10 N. The texture was evaluated during wear using an X-ray diffraction inverse pole figure technique for a range of sliding distances. Pole density distributions for the [0001] and [111] poles for of Ti and Al, respectively, were then determined from the inverse pole figures. The texture evolution during sliding wear was subsequently related to the friction and wear behaviour. For the aluminum sample, a (111) texture developed parallel to the worn surface with increasing sliding distance (a six-fold increase in the (111) pole density as the sliding distance increases from 0 to 2714 m). The titanium sample (normal section) which had a preferred orientation with the basal poles, [0001], parallel to the contact surface prior to testing, an increase in wear, i.e. sliding distance, did not change the texture. However, for the transverse section of titanium, the basal pole, [0001], density parallel to the worn surface increased with increasing sliding distance. The shape of the coefficient of friction versus sliding distance curve was strongly influenced by crystallographic texturing. A drop in the coefficient of friction with the progressive development of the [111 ] and [0001] texture was observed for both Al and Ti (transverse section), respectively, as a result of easy glide planes becoming parallel to the sliding plane.