The Development of Novel Cu/GO Nano-Composite Coatings by Brush Plating with High Wear Resistance for Potential Brass Sliding Bearing Application

Abstract

Low friction and high wear resistance are critical properties for sliding bearings. In this research, advanced Cu/GO nanocomposite coatings have been developed by a brush plating method to improve the tribological performance of brass-based sliding bearings. A series of brush plating studies under voltages from 2 to 6 V with different GO concentrations (0.2-0.8 g/L) was conducted, and the coating microstructures were characterised by SEM, EDX, GDOES and XRD and the tribological behaviour of the Cu/GO composite coatings were evaluated using dry ball-on-plane tribological tests The experimental results have demonstrated that GO can be successfully introduced into the whole composite coating layer; the Cu/GO composite coatings can reduce the friction of brass and increase its wear resistance by two orders of magnitude, mainly due to the self-lubricating GO added into the coatings.

Keywords: Cu/GO composite coatings; brass sliding bearing; electron brush plating; tribological properties.

Figure 1

Surface morphology of coating samples: (a) Cu2; (b) CuGO2; (c) Cu5; (d) CuGO5.

Figure 2

Surface roughness of (a) Group 1 and (b) Group 2 samples (see Table 1 for sample details), Ra of brass for comparison.

Figure 3

Typical SEM images of coating layer structures (a) Cu4 and (b) CuGO5 samples. (c,d) typical SEM images of well-developed columnar structures of CuGO samples showing GO within the lamellar layers. (e) GDOES depth profiles of carbon concentration, showing introduced GO content.

Figure 4

Cu and CuGO coating layer thickness under processing voltages of 2–6 V.

Figure 5

XRD patterns of (a) Cu and (b) CuGO samples. TEM microstructure (c) and (d) corresponding SAD pattern of sampleCuGO5.

Figure 6

Coefficient of friction (COF) of Cu and CuGO samples compared with brass sample.

Figure 7

(a) 2D scanning of the wear tracks, and wear volume loss of (b) Group1 and 2 coating samples, comparing with brass substrate.

Figure 8

Typical wear tracks of brass and coating samples: (a) Brass (in insertion, EDX mapping showing brass transferred to the count-part stainless steel ball surface); (b) coating CuGO5. Sliding direction is shown by blue arrows.

Figure 9

SEM images of wear tracks from (a) Cu5 and (b) CuGO5 samples. (c) EDX composition (carbon and oxygen only) analysis from wear tracks (denoted as 1, 2 in (a,b)) and wear debris (denoted as 3, 4 in (a,b), and (d) Raman spectra from wear tracks of Cu and CuGO5 samples.