Mechanical and Tribological Properties of PEEK Coatings with Different Melt Indexes Prepared by Electrostatic Powder Spray Technique

Poly-ether-ether-ketone (PEEK) coatings with different melt indexes (MI) were prepared on the stainless steel substrate via electrostatic powder spraying method. Amorphous coatings were obtained by quenching the as-melted coatings into the ice-water medium. Semi-crystalline coatings were obtained by annealing the amorphous coatings in an oven for 30 min at 260 degrees C. The XRD results indicates that the structure of PEEK coatings transforms from amorphous to semi-crystalline via the treatment of annealing. The hardness and the behavior friction of the PEEK coatings were tested. The result demonstrates that by the same treatment, the PEEK coatings with larger MI have higher crystallinity. The semi-crystalline PEEK coatings have higher hardness, lower friction coefficient and better wear rate than the amorphous ones. The poor fluidity of PEEK-A with lower MI leads to the rough coatings. Both of the PEEK-B and PEEK-C with larger MI can form smooth coatings and the friction coefficients and wear rates of them are stable. The friction coefficients of semicrystalline coatings B and C are less than 0. 15, and the wear rates are less than 20x10(-6) mm(3)/(N center dot m). Therefore PEEK with larger MI is more suitable for the preparation of PEEK coating by electrostatic spraying.