Y. Zhu, Y. Liu, Xingyu Wei
May 15, 2021
Abstract In this study, by producing the dual titanium boride (TiB2 +TiB) layers (DTBLs) on titanium alloy using solid-state boriding with rare earth additions (REs), the friction tests with two different counter-materials (GCr15 and Al2O3) were conducted. It is found that solid-state boriding of titanium alloy with REs can achieve better tribological properties than that of conventional one, without REs; furthermore, with the size of TiB whiskers decreasing, the tribological properties was further improved. To illustrate the size effect of TiB whiskers on the tribological properties, a novel surface uniaxial compression model of DTBLs was developed; then, a surface wear model using Archard wear equation was proposed to quantitatively estimate such size effect of TiB whiskers. It indicates that the above two models can adequately explain the mechanism of the size effect of TiB whiskers on the mechanical and tribological properties. The results of this study showed that the improvement of tribological performance of DTBLs was dominated not only by the “hard” TiB2 layer but also by the “soft” shear accommodating TiB layer; when the size of TiB whiskers is closed to the sub-micron scale, fine-grain strengthening effect would become obvious, causing the tribological properties further improved.