Effects of CaCO3 whisker on the sliding wear behaviour of poly(etheretherketone) under water-lubricated condition

Abstract

Polyetheretherketone (PEEK) composite specimens filled in 0–30 wt% content of CaCO3 whisker were prepared by compression moulding. Tribological testing of composites was carried out on an MM200 block-on-ring apparatus in water lubricated wear mode against carbon steel. The morphologies of wear traces were observed by scanning electron microscopy (SEM). The effects of CaCO3 whisker on the mechanical and tribological properties of composites were investigated. It was revealed that the inclusion of CaCO3 whisker significantly improved the wear resistance and reduced the friction coefficient of PEEK composites under water-lubricated condition. With an increase in CaCO3 whisker contents, the friction coefficient decreased and showed minima for 15 per cent CaCO3 inclusion. The specific wear rate of composites showed minima as 2.04×10−6 mm3/N m for 20 per cent CaCO3 inclusion as 5.2 per cent of that for pure PEEK, followed by a slow increase for further CaCO3 whisker addition. In terms of friction applications under water lubrication, when the tribological and mechanical properties were combined, the optimal content of CaCO3 whisker in the filled PEEK should be recommended as 15–20 per cent. The SEM observation of the wear traces indicated that CaCO3 whisker contributed to increase the load-carrying capacity and abate the scuffing and adhesion of filled composites, which conformed to the better wear resistance of CaCO3/PEEK composites than pure PEEK. No transfer film could be observed on the counterface of the mating ring under water-lubricated condition. It is confirmed that the transfer film is not the main reason for the enhancement of wear resistance of the composites in water lubrication.