Fabrication and properties of a lubrication composite coating based on poly(p-hydroxybenzoic acid) (PHBA)

摘要

The present paper describes an approach for fabricating smooth, compact and homogeneous composite coatings of PHBA/PA/MoS_2 on test blocks. The tribolog_ical behaviors were tested on a ring-block machine. For the PHBA/PA 6,6/MoS_2 coating of 20 wt.% PA 6,6 and 30 wt.% MoS_2 with the thickness of 20-40 _m, the steady friction coefficient was approximately 0.04 with the lowest wear loss while sliding against AISI 1045 steel ring. The PHBA in coating was synthesized in situ at 200 °C for the first step and 260 °C for the second. The chemical struc_tures and thermal properties of the obtained PHBA were characterized by means of Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorime_try/thermogravimetry (DSC/TG). The results showed that the chemical structure of the obtained PHBA was identical to that of the commercial PHBA powder despite that the decomposition temperature and the crystal transition tem_perature of the former were approximately 10-20 °C lower than that of the latter. The influence of nominal pressure and sliding velocity on the friction coefficient (_) and wear volume loss of the coatings was investigated. The results displayed that μ increased with the increase of sliding velocity, while it decreased when the nominal pressure was increased. For the volume loss, it increased with both the increase of speed and pressure.