Tribological Performance of B ₄ C‐hBN/TC4 Titanium Alloy Pair in Seawater: Influence of Sliding Speed

The effect of sliding velocity on the tribological performance of a B 4 C‐hBN/TC4 titanium alloy tribo‐pair is systematically investigated in artificial seawater. Worn surfaces and the chemical composition of the tribofilm are characterized by scanning electron microscopy, 3D profilometry, energy‐dispersive X‐ray spectroscopy, Raman, and X‐ray photoelectron spectroscopy. Results show that a 30 wt% hBN content yields the lowest coefficient of friction (COF) and wear rate. As the rotational speed increases from 510 to 750 r min −1 , the lubrication regime transitions from boundary to mixed, leading to a steadily decreasing COF. This phenomenon is directly linked to the formation and stabilization of a protective tribofilm. The film, rich in low‐shear‐strength compounds such as Ca(OH) 2 , Mg(OH) 2 , CaCO 3 , and H 3 BO 3 , effectively lubricates and protects the contact surfaces. However, further increasing the speed to 1 000 r min −1 generates excessive frictional heat at the contact interface. This thermal effect degrades the protective tribofilm by reducing its viscosity and thickness, ultimately compromising its integrity. As a result, the lubrication regime fails, leading to a deterioration in tribological performance, as evidenced by a sharp increase in the COF.