Amorphous boron coatings, ranging in thickness from 4 to 15 μm, have been synthesized via plasma-enhanced chemical vapor deposition using an rf plasma coil having serpentine rather than helical geometry for inductive coupling of the plasma. The power input to the rf coil has been established at five discrete levels ranging from 50 to 200 W during deposition from diborane onto Ti-6Al-4V substrates at 450°C. Deposition rates have been found to depend significantly on coil input power, reach in a saturation level of 15 μm/h at 100 W and higher but decreasing markedly with lower coil power levels. The amorphous nature of the coatings has been confirmed by selected area electron diffraction of extracted particles. Vickers and ultralow-load indentation experiments have been performed on boron coatings in cross-sectional and plan orientations, respectively. The ultralow-load hardnesses of the coatings deposited at all power levels exhibited relative independence from deposition power and ranged from 11.5 to 14.6 GPa. Vickers indentation in cross section produced hardnesses which were significantly greater than those using ultralow loading and an inconsistent dependence on deposition power.