Laser cladding of manganese oxide doped aluminum oxide granules on titanium alloy for biomedical applications

Due to the low hardness and poor tribological behavior of titanium alloys, surface coating is a very critical technique in order to increase their commercial exploitation. In this case, Al2O3-based coatings are very promising for these alloys to improve their surface properties. To increase the absorption of the laser light in the visible range, MnO2 is proposed as a dopant for Al2O3, in order to achieve dense coatings on Ti6Al4V substrates via cladding with a JK fiber laser. To ensure a homogeneous doping, MnO2 and Al2O3 were dispersed by means of ammonium citrate, and to fully cover the substrate, spray dried MnO2 doped Al2O3 granules were prepared and applied to the substrate. The effects of the solid loading on the properties of these granules were investigated. It is found that with 1.0 wt% MnO2 addition, a dense and uniform Al2O3 layer, accompanied with an interlayer, was successfully fabricated through laser cladding with low laser power of 20 W. Owing to the better adhesion on the substrate, Al2O3 coating on sandblasted substrates feature a higher hardness of 1204.1 ± 66.9 HV0.05 and an elastic modulus of 212.0 ± 11.8 GPa, which is an increase of 165.5% and 53.3%, respectively, compared to the as-received substrate.