Polyether ether ketone (PEEK) is widely used in aerospace applications because of its excellent physical and mechanical properties. However, given its intrinsic viscoelasticity and low hardness, PEEK is prone to wear failure. To address this problem, a carbon-based film deposition technology is typically applied. Among these films, diamond-like carbon (DLC) films have attracted considerable attention owing to their high hardness, good wear resistance, and chemical inertness. Using a linear ion beam combined with direct current magnetron sputtering technology, W-DLC films with different doping contents were prepared on PEEK by varying the Ar / C2H2 flow ratios from 68 / 12 to 62 / 18. The effects of the gas flow ratio on the composition, microstructure, and mechanical and friction properties of the PEEK / W-DLC composites were systematically examined. The SEM and HRTEM results showed that as the Ar / C2H2 flow ratio decreased, the deposition rate of the film gradually increased, the carbon clusters densified and their size increased. As the gas flow ratio decreased, the size of W clusters decreased, leading to a decline in the content of highly crystalline WC1-x. Moreover, when compared with pure PEEK, the surface wrinkle density of the PEEK / W-DLC composites increased and mechanical interlock structures were formed at the interface. The X-cut test showed that as the gas flow ratio decreased, the interfacial adhesion weakened, and the peeling of the films tended to become obvious. The XPS data showed that the W content decreased from 7.08at.% to 2.63at.%. The increase in C content resulted in the formation of more C-C bonds, and some of C=O bonds preferentially transformed into C-O bonds. With a decrease in the gas flow ratio, the W0 content decreased, whereas the W5+ / W6+ content increased slightly. This indicated that the W element in the film tended to exist in the form of W carbides. Raman analysis showed that ID / IG decreased from 0.42 to 0.32, the sp2 content and cluster size decreased accordingly. The full width at half maximum (FWHM) of G peak increased from 62.67 cm−1 to 71.26 cm−1, indicating that the incorporation of W atoms could aid in reducing the structural disorder in films. As the gas flow ratio decreased, the hardness (H) and elastic modulus (E) of the PEEK / W-DLC composites reached to 5.25 and 30.23 GPa, respectively. Compared to pure PEEK, the values of H and E both increased by an order of magnitude. When the gas flow ratio was 66 / 14, the H / E and H3 / E2 of the composite corresponded to 0.2 and 0.17, respectively, which were approximately two orders of magnitude higher than those of pure PEEK. This implied that the composite had strong fracture toughness and good elastic-plastic deformation resistance. Compared with other samples, the W-DLC films prepared with 66 / 14 flow ratio exhibited better tribological properties with a low wear rate of 1.52×10−8 mm3 / (N·m). This was mainly owing to the mechanical protection of the carbon films (improving wear resistance) and W-rich lubrication transfer film formed at the wear scars (reducing friction factor). By analyzing the formation mechanism of the pits on the PEEK / W-DLC composites, it was determined that owing to the viscoelasticity of PEEK and the generation of wear debris of W-DLC films, both adhesive wear and abrasive wear occurred during the friction process. The pits that formed on the wear tracks mainly existed in the following three forms: the first type of pit was mainly composed of C elements, while the distributions of O, Fe, and W elements were hardly observed. This indicated that during the friction process, the wear debris of W-DLC films formed C-rich clusters. These C-rich clusters were embedded in the low-hardness PEEK substrate by frictional compressive stress. The second type of pit was mainly composed of C and O elements, whereas W and Fe elements were rarely distributed. These pits were caused by the peeling of W-DLC films, which led to the exposure of PEEK substrate. The third type of pit was mainly composed of C, O, and Fe elements, while the presence of W element was relatively rare, and Fe element was concentrated on the convex part of the pits. The convex part was formed by the accumulation of wear debris in the pits. This showed that the first type of pit further caused abrasive wear on the grinding ball due to the convex part. This research not only reveals the structural evolution and wear failure mechanism of carbon-based films on PEEK, but also guides the design of high-efficiency wear-resistant aerospace materials. © 2024 Chinese Mechanical Engineering Society. All rights reserved.
