In-situ synthesized Ni-Zr intermetallic/ceramic reinforced composite coatings on zirconium substrate by high power diode laser

Ni-Zr intermetallic/ceramic reinforced composite coatings were in-situ synthesized by laser cladding series of Ni-Cr-B-Si powders on zirconium substrate. Microstructure, phase constituents and microhardness of coatings were investigated by means of optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and microsclemeter. Results indicated that coatings with metallurgical bonding to substrate consisted of cellular NiZr matrix and massive reinforcements including NiZr2, Zr-5 (SixNi1-x)(4) and ZrB2. Morphologies of reinforcements were mainly dominated by temperature gradient and cooling rate from surface to bottom of the coating produced by same powder. In different coatings, microstructure and forming of ZrB2 mainly depended on affinity of elements and Si/B ratio in different powders. In addition, the mean microhardness of coatings up to 1200-1300 HV0.2 is nearly 7 times higher than that of R60702 zirconium substrate. (C) 2014 Elsevier B. V. All rights reserved.