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.