Microstructure of laser cladding multi-layer Nb-Si-Ti

The microstructure and composition design of the niobium silicide based composites which prepared by direct laser fabrication based on multi-layer laser cladding through optimizing laser scanning parameters and adjusting the composition ratio of the mixed element powders were investigated. Element powders mixture Nb-18Si-24Ti (at.%) was prepasted on a substrate of Ti-6Al-4V and scanned by a 500 W pulsed Nd:YAG laser. Four-layer specimens were fabricated under the optimized laser processing parameters with electric current of 225A, laser scanning speed of 3.0 mm/s, pulsed frequency of 15Hz, defocus length of 15 mm. Microstructures and phases of the prepared specimens were analyzed by OM, SEM and XRD, respectively. Results showed that Nb5Si3, Nb3Si and Nbss are formed in the multilayer laser cladding coatings. With the increase of the number of layers, the Nb and Si contents increase gradually, tiny dendrites are found in the layer near the substrate while the top layer contain island-shape grey phases distributed in the continuous white phases. ©, Northeastern University. All right reserved.