Micro-abrasion of filled and unfilled polyamide 11 coatings

In this study, five polyamide (PA11) based coatings have been investigated; two filled with different types of solid fillers (TiO2) and in different proportions, and two unfilled coatings, deposited onto carbon steel substrates. Tests were conducted using a Phoenix Tribology TE99 micro-abrasion tester. A 25 mm diameter hardened and pitted carbon steel ball was loaded against the sample and rotated in the presence of 5 mum silicon carbide (SiC) abrasive slurry with a solids concentration of 0.375 g/cm(3). Tests were conducted under optimum conditions for grooving (two-body) abrasion. The wear rates are presented as a function of load, total sliding distance and mechanical properties of the coating. The influence on coating performance of air-cooling and water-cooling the coating after deposition is explored. The unfilled coatings exhibited a specific wear rate (k) about 1.3 times lower than the filled coatings. The results, contrary to expectations, show that the fillers do not act as load-bearing elements within the coating matrix. The value of k decreased with increasing load for all the coatings but an irregular trend in k was observed as a function of sliding distance. Detailed scanning electron microscopy was performed on the wear scars to identify the wear mechanisms and the role of the fillers. (C) 2004 Elsevier B.V. All rights reserved.