Boron carbide has been successfully deposited on Ti alloy by vacuum plasma spraying (VPS). Mechanical properties of the deposited structure were assessed by micro-hardness and nano-hardness indentation. Chemical and phase compositions of the starting powder and the as-sprayed structure were characterized using hot gas extraction (LECO), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and Raman spectroscopy. The microstructure consisted of equiaxed boron carbide grains, microcrystalline boron carbide particles, and amorphous carbon regions at the grain boundaries. The amount of boron oxide and amorphous carbon increased during spraying. Carbon segregation to grain boundaries in the as-deposited B4C was observed. The measured micro-hardness was slightly higher than values previously reported (1033 ± 2009 HV). There was significant variation of nano-hardness from point to point in the material due to the existence of multiple phases, splat boundaries, and porosity in the deposited structure.