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Detailed experiments have been conducted to produce a nickel-based alloy composite coating reinforced with TiC particles on medium carbon steel substrate by powder feeding laser cladding using a coaxial nozzle. The chemical compositions, microstructures and surface morphology of the coatings were analyzed using scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS) and X-ray diffractometry (XRD). Composite coatings with TiC particles of various shapes and sizes embedded in nickel-based alloy were synthesized in-situ during laser processing. An excellent bonding between the coating and the carbon steel substrate was obtainable. The coatings were uniform, continuous and free from cracks. The microstructure of the coating was mainly composed of γ-Ni dendrites, a small amount of CrB, Ni3B, M23C6 and dispersed TiC particles. The maximum microhardness of the coating was about HV0.21200. [Copyright &y& Elsevier]

Abstract: Fe-based composite coatings reinforced by in situ synthesized particles have been produced by laser melting a precursor powder mixture of Fe-based alloy powder, Ti, Zr and C. The microstructure of the coating is typically hypo-eutectic, which consists of martensite, residual austenite, ledeburite and dispersed in situ carbide particles. The experimental results show that laser melting a precursor containing both Zr and Ti is favorable to form particles in the maximum volume fraction compared with those containing either of them. The particles are investigated to be multiple carbides. [Copyright &y& Elsevier]

In order to improve resistance to high temperature and wear resistance of pure aluminum, laser-cladding experiments were conducted on a 3 kW continuous wave CO2 laser to produce in situ synthesized molybdenum silicide (MoSi2)/SiC composite coatings on pure aluminum. The laser consolidified microstructure and phase evolution were investigated using scanning electron micrograph and X-ray diffraction (XRD). The in situ formation of MoSi2/SiC was carried out by adding a mixture of Mo, Si and C precursor powder layer followed by melting the layer and substrate under a laser beam. The experimental results showed that these compounds, MoSi2 and SiC, can be formed from three distinct powders of Mo, Si and C on Al alloy, and, provided that supplied energy is sufficient to start the reaction between the initial products, a good metallurgical bond between coating and the substrate can be achieved. The microstructures of the coating were composed of MoSi2, Mo5Si3 and SiC phases. The microhardness of coating was about 12 times that of the aluminum substrate, the maximum value reached HV0.2 1200. [Copyright &y& Elsevier]

Abstract: This paper reports an investigation into the mechanisms of three-dimensional manganese-based nanoporous structure (3D-Mn-NPS) fabricated by laser deposition of Mn–Cu precursor followed by selective dealloying of Cu component. The micro/nano-structures of both the precursor alloy and the post-dealloying 3D-Mn-NPS are characterized. It has been found that compositional inhomogeneity in the precursor alloy is crucial to the final structure of 3D-Mn-NPS. Additionally, the formation of 3D-Mn-NPS is a coupled process of nanopore/nanoligament development and Mn oxidation. The insights from the study on the formation of our 3D-Mn-NPS can be extended to guide the design and fabrication of other nanoporous metals. [Copyright &y& Elsevier]

Abstract: Nanoporous metals (NPMs) hold great promise for various applications. However, lack of understanding of NPMs'' thermal response hinders their potentials in high temperature applications. In this letter, we study the thermal stability of the three-dimensional manganese-based nanoporous structure (3D-Mn-NPS) recently developed by our group using a novel laser processing–dealloying method. We determine the melting point of the 3D-Mn-NPS to be within the range of 513–593K, significantly lower than that of the bulk alloy (1373–1473K). We also establish the structural evolution history of the 3D-Mn-NPS under thermal processing. The nanomorphology evolves from nanowire skeletons into nanowire–nanoparticle complex and then into agglomerates of nanoparticles. [Copyright &y& Elsevier]

Abstract: In this study, epoxy resin was used as adhesive material to strengthen the bandaged joint of double-walled carbon nanotube (DWNT) strands in a solution mixing way. As the concentration of soaking solution rises from 10 vol.% to 50 vol.%, the average tensile strength and Young''s modulus of the composite joint increase and reach as high as 379 MPa and 17.1 GPa, which are improved by the factors of 1 and 1.6 compared with those of the original joint, respectively. This reinforcement of original joint can be attributed to stronger bonding and better load transfer between the DWNT bundles inside the composite joint induced by intercalated epoxy resin, which is further proved by Raman study on D′ band. [Copyright &y& Elsevier]