Tribological Properties of Water-lubricated Rubber Materials after Modification by MoS2 Nanoparticles

Abstract

Frictional vibration and noise caused by water-lubricated rubber stern tube bearings, which are generated under extreme conditions, severely threaten underwater vehicles' survivability and concealment performance. This study investigates the effect of flaky and spherical MoS₂ nanoparticles on tribological properties and damping capacity of water-lubricated rubber materials, with the aim of decreasing frictional noise. A CBZ-1 tribo-tester was used to conduct the sliding tests between rubber ring-discs and ZCuSn₁₀Zn₂ ring-discs with water lubrication. These materials' typical mechanical properties were analysed and compared. Coefficients of friction (COFs), wear rates, and surface morphologies were evaluated. Frictional noise and critical velocities of generating friction vibration were examined to corroborate above analysis. Results showed that spherical MoS₂ nanoparticles enhanced rubber material's mechanical and tribological properties and, in turn, reduced the friction noise and critical velocity. Flaky MoS₂ nanoparticles reduced COF but did not enhance their mechanical properties, i.e., the damping capacity, wear resistance property; thus, these nanoparticles did not reduce the critical velocity obviously, even though increased the frictional noise at high load. The knowledge gained in the present work will be useful for optimizing friction pairs under extreme conditions to decrease frictional noise of water-lubricated rubber stern tube bearings.

Figure 1

SEM images of (a) flaky MoS₂ nanoparticles and (b) spherical MoS₂ nanoparticles, (c) x-ray diffraction patterns of the three materials.

Figure 2. Typical mechanical property behaviours of the three rubber materials.

Their (a) shore harnesses, (b) tensile strengths, (c) tear strengths under different temperature environments, and (d) their stress-compression curves at the compressive strain rate of 2640 s⁻¹ and room temperature.

Figure 3

Trends in the (a) storage modulus, (b) loss modulus, and (c) loss factor of the three rubber materials under different temperature conditions.

Figure 4

Payne effects of the (a) storage modulus, (b) loss modulus, and (c) loss factor for the three rubber materials under different strain amplitudes with a frequency of 10 Hz at room temperature (25 °C).

Figure 5. Effect of different MoS₂ nanoparticles on the average COFs between the rubber and ZCuSn₁₀Zn₂ ring-discs.

Figure 6. Effects of different MoS₂ nanoparticles on the average distance wear volumes of the rubber ring-discs.

Figure 7

SEM images of the wear surfaces of tested NBR ring-discs at (a) 0.055, (b) 0.55, and (c) 3.3 m/s.

Figure 8

SEM images of the wear surfaces of tested NBR-FMS ring-discs at (a) 0.055, (b) 0.55, and (c) 3.3 m/s.

Figure 9

SEM images of the wear surfaces of tested NBR-SMS ring-discs at (a) 0.055, (b) 0.55, and (c) 3.3 m/s.

Figure 10. Frictional noise and vibration characteristics of the three rubber ring-discs at room temperature.

(a) Critical velocities of the frictional vibration of the three rubber materials under different applied loads; (b) frictional noise of three rubber materials at 0.3, 0.9 MPa and 0.22 m/s; frequency-domain spectrum after filtering of three rubber materials at (c) 0.3, (d) 0.9 MPa and 0.22 m/s.

Figure 11

Tension models of (a) flaky MoS₂, (b) spherical MoS₂ nanoparticles and rubber material.

Figure 12. Lubrication mechanism models of the flaky and spherical MoS₂ nanoparticles for rubber material.

(a) Raman spectroscopy of the ZCuSn₁₀Zn₂ ring-discs’ wear surfaces tested against the three rubber materials at 0.055 m/s and 0.3 MPa; (b) EDS of the ring-discs’ wear surfaces; (c) lubrication mechanism model of the flaky MoS₂ nanoparticles; (d) lubrication mechanism model of the spherical MoS₂ nanoparticles.

Figure 13

(a)Friction forces, (b) distance wear volumes of the three rubber materials under 0.3, 0.9 MPa and 0.22 m/s and (c) average loss factors of the three rubber materials in the range from 0 °C to 80 °C.