Effect of Hardness Ratio on the Wear Performance and Subsurface Evolution of Ni₃Al Matrix Composites

ABSTRACT

A favorable hardness ratio (H_disk/H_pin = H_d/H_p) could lead to a transition to mild wear during sliding contact. To determine a more appropriate H_d/H_p value for the sliding wear, the dry sliding pin-on-disk wear tests of Ni₃Al matrix composites (NMCs) with multilayer graphene (MLG) are undertaken at H_d/H_p values of 0.99, 0.83, 0.42, and 0.35 at sliding speeds of 0.1, 0.3, 0.5, and 0.7 m/s. It is found that the tribological properties of NMCs are strongly affected by the various hardness ratios. At 0.1 m/s, the friction coefficient decreases with a decrease in H_d/H_p value. The low friction coefficient is 0.14 and the wear rate is 0.9 × 10⁻⁵ mm³ N⁻¹m⁻¹ under the ceramic counterpart with H_d/H_p of 0.35. At 0.7 m/s, the tribological properties show the opposite trend with a decrease in H_d/H_p. At an H_d/H_p of 0.35, the smooth compact layer on the worn surface could decrease the friction at 0.1 m/s, and the improved hardness in the subsurface by strain hardening would play an important role in the improvement of wear resistance. Under the metal counterpart with H_d/H_p of 0.99, plastic deformation only occurs on the contact surface and the MLG could suppress further shear deformation in the subsurface, leading to a low wear rate (2.4 × 10⁻⁵ mm³ N⁻¹m⁻¹) and friction coefficient (0.15) at 0.7 m/s.

KEYWORDS:

• Solid lubricants
• self-lubricating composites
• self-lubrication friction
• solid lubrication wear
• self-lubrication

Acknowledgments

The authors also wish to thank the Material Research and Testing Center of Wuhan University of Technology for their assistance.

Funding

This work was supported by the National Natural Science Foundation of China (51275370) and the Fundamental Research Funds for the Central Universities (2014-yb-004).