Constructing Serrated Boride Composite Layer for Enhancing Wear Resistance of Ti6Al4V Alloy

ABSTRACT Appropriate configuration combined with strong interface bonding is the essential requirement for developing high wear‐resistant coatings. Herein, based on the powder‐pack boriding process, the properties of Ti6Al4V alloy are effectively improved by constructing a serrate tribological boride composite layer. Scanning electron microscope (SEM) and transmission electron microscope (TEM) results demonstrated that in situ serration boride layer distributes on the surface of Ti6Al4V alloy (including the outer TiB 2 layer and the inner TiB whisker layer), forming a coherent/semi‐coherent TiB 2 ‐TiB‐Ti transition interface during the heat treatment. Ti matrix grains beneath the boride layer are firmly riveted and composites achieve excellent friction coefficient about 0.40 ± 0.01. The formation mechanism of serration boride layer was discussed based on thermodynamic and diffusion kinetic analysis. Moreover, first‐principles calculations showed that the creative serrated configuration improves the interfacial bonding of the boride layer and matrix. Electron backscatter diffraction (EBSD) and geometric phase analysis (GPA) were employed to investigate the influence of the serrated boride layer on deformation behavior of composites. It revealed that the serrated boride layer reduces internal stress of interface region and can stimulate the plastic deformation of Ti matrix grains. More importantly, the strongly bonded TiB 2 ‐TiB‐Ti interface directly changes the fracture mechanism of boride layer. The current work provides a novel avenue for the fabrication of high wear‐resistant Ti alloy.