Microstructural characterization of NiCr1BSiC laser clad layer on titanium alloy substrate

Laser cladding of NiCrBSiC powders on Ti–6Al–4V alloy substrate was carried out, and the microstructure of the laser clad layer was characterized by TEM and SEM. Results show that the phases of TiC, TiB2, CrB and M23C6 were formed in situ in the clad layer. The TiC phase exists in the form of dendrites with two types of interface morphology including the non-faceted and the faceted one. The TiB2 phase nucleates on the facets of TiC dendrites, and can grow to form a special morphology of microstructure in which the TiC dendrite is encased by the TiB2 phase. The CrB and M23C6 phases exist in the form of rod-shaped morphology, inside which stacking faults could be observed. The clad layer matrix consists of primary γp-Ni dendrites and lamellar eutectics of γe-Ni+Ni3B. The formation mechanism of the microstructure of the clad layer was discussed.