Inhibiting low-dimensional defects of titanium diboride coatings by Si incorporation: Toward enhanced corrosion resistance and mechanical properties

• Elemental doping is used to regulate structure and reduce defects of coatings. • The hardness of the coating is enhanced by solution strengthening. • The corrosion resistance can be improved by reducing low-dimensional defects. • Reducing low-dimensional defects can inhibit transverse corrosion interior of the coating. • The formation of amorphous phase reduces the corrosion resistance and hardness. Hard and anti-corrosive coatings can provide effective protection for marine components, but low-dimensional defects (LDDs) in the coatings would reduce the performance thus limit the application of the coatings. This work attempts to reduce the LDDs by Si doping to improve the corrosion resistance and mechanical properties of magnetron sputtered titanium diboride coatings. Results reveal appropriate Si doping (5.4 at.%) can obviously enhance the quality of the coating and reduce the LDDs, but excessive Si doping (8.6 at.%) will lead to the formation of new LDDs because of the appearance of amorphous phase. The electrochemical measurements with 3 days and 30 days prove that the corrosion resistance of the coating can be significantly improved when the LDDs are reduced. Reducing LDDs can inhibit the corrosion of Cl - due to the reducing of penetrable sites, and even limit the growth of pinholes by inhibiting transverse corrosion interior of the coating. The hardness can be improved due to solid solution strengthening by Si doping, but decreases when forming a soft amorphous phase.