Laser cladding of Ni-base composite coatings onto Ti–6Al–4V substrates with pre-placed B4C + NiCrBSi powders

NiCrBSi + 5 wt.%B4C powders were pre-placed and then laser clad onto Ti–6Al–4V substrates. Microstructure and morphology of the coatings were examined using an X-ray diffractometer, an electron probe X-ray microanalyzer and a scanning electron microscope with an energy dispersive spectroscopy. The microhardness of the coating was measured using a Vickers hardness tester. After laser cladding, a good metallurgical bond without cracks and pores was obtained. A reaction between B4C and Ti occurred, leading to an in-situ synthesis of TiB2 and TiC reinforcements in the coating. The coating mainly consists of γ-Ni as the matrix phase and TiB2, TiC and CrB reinforcements. The average microhardness of the composite coating is HV 1300 and it is three times higher than that of the Ti–6Al–4V substrate.