Microstructural evolution of titanium matrix composite coatings reinforced by <Emphasis Type="Italic">in situ</Emphasis> synthesized TiB and TiC by laser cladding |
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Authors: | Jun Li Zhi-shui Yu Hui-ping Wang Man-ping Li |
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Institution: | (1) State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200030, P.R. China;(2) Materials and Engineering, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai, 200030, P.R. China |
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Abstract: | Titanium-based composite coatings reinforced by in situ synthesized TiB and TiC particles were successfully fabricated on Ti6Al4V by laser cladding using Ti-B4C-Al or Ti-B4C-C-Al powders as the precursor materials. The microstructural and metallographic analyses were made by X-ray diffraction
(XRD), optical microscope (OM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The results show
that the coatings are mainly composed of α-Ti cellular dendrites and a eutectic transformation product in which a large number
of coarse and fine needle-shaped TiB and a few equiaxial TiC particles are homogeneously embedded. A thin dilution zone with
a thickness of about 100 μm is present at the interface, and it consists of a few TiB and TiC reinforcements and a large number
of lamella grains growing parallel to the heat flux direction in which a thin needle-shaped microstructure exists due to the
martensitic transformation. The microstructural evolution can be divided into four stages: precipitation and growth of primary
β-Ti phase, formation of the binary eutecticum β-Ti+TiB, formation of the ternary eutecticum β-Ti+TiB+TiC, and solid transformation
from β-Ti to α-Ti. |
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