Surface energy slider coatings

FIGURE 4.7 Results of subambient pressure frictional hysteresis loop tests on low surface energy slider coatings (a) uncoated, (b) PFOM coated, (c) ZNa coated, and (d) FCOC coated. 

Overall, the tribological tests provide a ranking for the performance of the low-surface-energy slider coatings ... 

Three metrics were employed to compare the performance of low-surface-energy coatings on sliders in the subambient pressure frictional hysteresis loop test (1) frictional hysteresis, (2) lubricant accumulation on the slider during the hysteresis test, and (3) disk scratches. The typical friction force on the slider during loop tests, each carried out with a separate slider, is shown in fig. 4.7. Four test runs were done, each... 

None of the low-surface-energy coatings completely prevented disk scratching or lubricant transfer to the slider in the subambient pressure frictional hysteresis loop test. Friction and hysteresis were nnaffected by the presence of the coating. 

The thick-flhn limit of the lubricant dispersion surface energy is yf = 13 mJ/m [22]. The dispersion component of the surface energy of the slider is Yi. For the uncoated slider, yf = 43 mJ / m, and the coated slider values are given in table 4.10. The adhesion stress is listed in table 4.13. Further discussion of adhesion-controlled friction is given in the literature [23]. 

The surface energy and tribological performance of poly (lH,lH-pentadeca-fluorooctyl methacrylate) fluorohydrocarbon surfactant were compared with several other types of slider coatings. The surface energy of the fluorinated acrylate polymer was the lowest, and it provides the best compromise for reduction of both lubricant transfer and scratches. The improvement is consistent with a reduction in the adhesion stress by the low-surface-energy coatings on the slider. 

The apparatus for the PFAM film coating on the slider surface is shown in Fig. 1 (a). The film thickness was measured by the TOF-SIMS as shown in Fig. 1 (b). It used a pulsed primary Ga+ ion beam to impact the surface of the PFAM film with an inset energy of 15 keV, an extractor current of 2 fj,A, beam current of 600 pA, a pulse width of 17.5 ns, and a frequency of 10 kHz, respectively. The positive TOF-SIMS spectra on the slider surface is shown in Fig. 2 where the peaks at m/z 31, 50, 69, 100, and 131 in Fig. 2(a) correspond to the positive secondary ion fragments of CF+, CFj, C2F4, and C3F5, respectively. The peak at m/z 469 apparent in Fig. 2(b) corresponds to the ion C12H7F 15O2H+ which is the characteristic ion of PFAM molecules. Therefore, the positive TOF-SIMS spectra demonstrates the existence of PFAM film [24,25]. The thickness of the PFAM film can be determined... 

The PTV is defined as the loss of energy as the standard rubber-coated slider assembly slides across the test surface and provides a standardised value of slip/skid resistance (CEN EN 13036-4 2011). 

---