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S. L. Dong - One of the best experts on this subject based on the ideXlab platform.

  • Laser cladding of Ti-6Al-4V alloy with TiC and TiC + NiCrBSi powders
    Surface & Coatings Technology, 2001
    Co-Authors: R.l Sun, L.x. Guo, D.z Yang, S. L. Dong
    Abstract:

    Abstract Laser cladding of Ti-6Al-4V alloy with TiC and TiC+NiCrBSi powders was carried out, and microstructure, as well as microhardness profile, in the clad layers was examined. The results showed that, in the TiC clad layer, TiC was melted and solidified to form dendrites in the clad Zone, and dissolved into the melted Ti-alloy substrate and precipitated to form well-developed dendrites in the Dilution Zone. With increasing specific laser energy, the Dilution effect of the Ti-alloy substrate was enhanced, and the microhardness decreased in both the clad and the Dilution Zones. In the TiC+NiCrBSi laser clad layers, TiC particles dissolved into the melted Ni-based alloy (binder material) in the clad Zone. With increasing specific laser energy, the degree of solution of TiC particles was increased. During cooling, fine spherical particles and dendrites of TiC precipitated from the Ni-based alloy. When the TiC volume fraction increased to more than 50%, clustering of TiC particles was observed in the clad Zone. The clustering of TiC particles resulted in a decrease in the homogeneity of the microstructure and microhardness distribution in the clad Zone. The Dilution Zone of the TiC+NiCrBSi clad layers is a mutually melted region of the Ni-based alloy and titanium-alloy substrate and presents a microstructure of dendrites.

  • microstructure and wear resistance of nicrbsi laser clad layer on titanium alloy substrate
    Surface & Coatings Technology, 2000
    Co-Authors: Dezhuang Yang, S. L. Dong
    Abstract:

    Abstract Laser cladding of NiCrBSi powders on Ti-6Al-4V alloy substrate was performed, and microstructure, microhardness and wear resistance of the clad layers were evaluated. Results show that the laser clad layer is divided into three regions: the clad, the Dilution and the heat-affected Zones. In the clad Zone, fine particles of TiB2, TiC and M23(CB)6 are distributed in the matrix of the primary γ-Ni and the multi-phase eutectics consisting of γ-Ni, Ni3B and silicides. Microhardness of the clad Zone is very high, being approximately HV 1000. The Dilution Zone is a mixture of melted Ni-base and Ti-base alloys, and possesses a characteristic of directional crystallization. The heat-affected Zone has an acicular martensitic structure, and the microhardness is HV 360–380. Compared to titanium alloy, the wear resistance of clad layer is improved. The mechanism of wearing of clad layer is a mixed type of slight peeling-off and abrasion.

L.x. Guo - One of the best experts on this subject based on the ideXlab platform.

  • MICROSCOPIC MORPHOLOGY AND MICROSTRUCTURE OFTi-NANDTi-NiPHASE BETWEEN THE Dilution Zone AND THE CLAD Zone IN LASER REMELTINGNiCrBSi/TiNLAYER ONTi-6Al-4VALLOY SURFACE
    Surface Review and Letters, 2004
    Co-Authors: Rongxiang Liu, L.x. Guo, T.q. Lei
    Abstract:

    The microscopic morphology and microstructure of Ti-N and Ti-Ni phase between the Dilution Zone and the clad Zone in laser remelting NiCrBSi/TiN layer on a Ti-6Al-4V alloy were characterized using TEM and SEM. The experimental results showed that during laser irradiation heating, TiN particles were partially dissolved into the melted Ni-base alloy, and the dissolved Ti and N atoms were precipitated in the form of TiN, TiN0.3. Ti exhibits height activity, it combines with Ni forming Ti2Ni, TiNi matrix intermetallic during laser remelting, faults exist in the Ti2Ni and TiNi phase, and crystal lattice of TiNi phase is superlattice. Lastly, the cause of the formation of the Ti-N and Ti-Ni phase is discussed.

  • STRATIFICATION MECHANISM AND INTERFACE CHARACTERIZATION OF (TiN), (TiC)/NiCrBSi COMPOSITE COATINGS SYNTHESIZED BY LASER REMELTING
    Surface Review and Letters, 2004
    Co-Authors: Rongxiang Liu, T.q. Lei, L.x. Guo
    Abstract:

    TiC/TiN-reinforced composite coatings were fabricated on the substrate of Ti–6Al–4V alloy using laser remelting. X-ray diffraction (XRD) was used to identify the phases in the laser-clad composite coating; the interface characterization of the Dilution Zone-clad Zone (IDC) and the Dilution Zone-heat-affected Zone (IDH) was observed with a scanning electron microscope (SEM). The results show that the microstructure of a cross-section has stratification characterization, and consists of the clad Zone (CZ), the Dilution Zone (DZ), the diffusion layer (DL) and the heat-affected Zone (HAZ). The layer-by-layer microstructure results from the boundary layer phenomenon of viscous melt-fluid and diffusion. The kind of reinforced particle has an effect on the interface morphology, microstructure and flow characterization of the melt-fluid. The phase constitution in the clad Zone consists of (Cr–Ni–Fe), TiC, Ni4B3, Ti2Ni, Cr2B and M23C6 for TiC+NiCrBSi coating, and (Cr–Ni–Fe), TiN, NiB, Cr2Ti and Ti2Ni for TiN+NiCrB...

  • Laser cladding of Ti-6Al-4V alloy with TiC and TiC + NiCrBSi powders
    Surface & Coatings Technology, 2001
    Co-Authors: R.l Sun, L.x. Guo, D.z Yang, S. L. Dong
    Abstract:

    Abstract Laser cladding of Ti-6Al-4V alloy with TiC and TiC+NiCrBSi powders was carried out, and microstructure, as well as microhardness profile, in the clad layers was examined. The results showed that, in the TiC clad layer, TiC was melted and solidified to form dendrites in the clad Zone, and dissolved into the melted Ti-alloy substrate and precipitated to form well-developed dendrites in the Dilution Zone. With increasing specific laser energy, the Dilution effect of the Ti-alloy substrate was enhanced, and the microhardness decreased in both the clad and the Dilution Zones. In the TiC+NiCrBSi laser clad layers, TiC particles dissolved into the melted Ni-based alloy (binder material) in the clad Zone. With increasing specific laser energy, the degree of solution of TiC particles was increased. During cooling, fine spherical particles and dendrites of TiC precipitated from the Ni-based alloy. When the TiC volume fraction increased to more than 50%, clustering of TiC particles was observed in the clad Zone. The clustering of TiC particles resulted in a decrease in the homogeneity of the microstructure and microhardness distribution in the clad Zone. The Dilution Zone of the TiC+NiCrBSi clad layers is a mutually melted region of the Ni-based alloy and titanium-alloy substrate and presents a microstructure of dendrites.

Dezhuang Yang - One of the best experts on this subject based on the ideXlab platform.

  • microstructure and wear resistance of nicrbsi laser clad layer on titanium alloy substrate
    Surface & Coatings Technology, 2000
    Co-Authors: Dezhuang Yang, S. L. Dong
    Abstract:

    Abstract Laser cladding of NiCrBSi powders on Ti-6Al-4V alloy substrate was performed, and microstructure, microhardness and wear resistance of the clad layers were evaluated. Results show that the laser clad layer is divided into three regions: the clad, the Dilution and the heat-affected Zones. In the clad Zone, fine particles of TiB2, TiC and M23(CB)6 are distributed in the matrix of the primary γ-Ni and the multi-phase eutectics consisting of γ-Ni, Ni3B and silicides. Microhardness of the clad Zone is very high, being approximately HV 1000. The Dilution Zone is a mixture of melted Ni-base and Ti-base alloys, and possesses a characteristic of directional crystallization. The heat-affected Zone has an acicular martensitic structure, and the microhardness is HV 360–380. Compared to titanium alloy, the wear resistance of clad layer is improved. The mechanism of wearing of clad layer is a mixed type of slight peeling-off and abrasion.

Clifford E. Smith - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Investigation of Enhanced Dilution Zone Mixing in a Reverse Flow Gas Turbine Combustor
    Journal of Engineering for Gas Turbines and Power, 1995
    Co-Authors: D. S. Crocker, Clifford E. Smith
    Abstract:

    An advanced method for Dilution Zone mixing in a reverse flow gas turbine combustor was numerically investigated. For long mixing lengths associated with reverse flow combustors (X/H > 2.0), pattern factor was found to be mainly driven by nozzle-to-nozzle fuel flow and/or circumferential airflow variations; conventional radially injected Dilution jets could not effectively mix out circumferential nonuniformities. To enhance circumferential mixing, Dilution jets were angled to produce a high circumferential (swirl) velocity component. The jets on the outer liner were angled in one direction while the jets on the inner liner were angled in the opposite direction, thus enhancing turbulent shear at the expense of jet penetration. Three-dimensional CFD calculations were performed on a three-nozzle (90 deg) sector, with different fuel flow from each nozzle (90, 100, and 110 percent of design fuel flow). The computations showed that the optimum configuration of angled jets reduced the pattern factor by 60 percent compared to an existing conventional Dilution hole configuration. The radial average temperature profile was adequately controlled by the inner-to-outer liner Dilution flow split.

  • Numerical Investigation of Enhanced Dilution Zone Mixing in a Reverse Flow Gas Turbine Combustor
    Volume 2: Combustion and Fuels; Oil and Gas Applications; Cycle Innovations; Heat Transfer; Electric Power; Industrial and Cogeneration; Ceramics; Str, 1993
    Co-Authors: D. S. Crocker, Clifford E. Smith
    Abstract:

    An advanced method for Dilution Zone mixing in a reverse flow gas turbine combustor was numerically investigated. For long mixing lengths associated with reverse flow combustors (X/H > 2.0), pattern factor was found to be mainly driven by nozzle-to-nozzle fuel flow and/or circumferential airflow variations; conventional radially injected Dilution jets could not effectively mix out circumferential non-uniformities.To enhance circumferential mixing, Dilution jets were angled to produce a high circumferential (swirl) velocity component. The jets on the outer liner were angled in one direction while the jets on the inner liner were angled in the opposite direction, thus enhancing turbulent shear at the expense of jet penetration. 3-D CFD calculations were performed on a three-nozzle (90°) sector, with different fuel flow from each nozzle (90%, 100% and 110% of design fuel flow). The computations showed that the optimum configuration of angled jets reduced the pattern factor by 60% compared to an existing conventional Dilution hole configuration. The radial average temperature profile was adequately controlled by the inner-to-outer liner Dilution flow split.Copyright © 1993 by ASME

R.l Sun - One of the best experts on this subject based on the ideXlab platform.

  • Laser cladding of Ti-6Al-4V alloy with TiC and TiC + NiCrBSi powders
    Surface & Coatings Technology, 2001
    Co-Authors: R.l Sun, L.x. Guo, D.z Yang, S. L. Dong
    Abstract:

    Abstract Laser cladding of Ti-6Al-4V alloy with TiC and TiC+NiCrBSi powders was carried out, and microstructure, as well as microhardness profile, in the clad layers was examined. The results showed that, in the TiC clad layer, TiC was melted and solidified to form dendrites in the clad Zone, and dissolved into the melted Ti-alloy substrate and precipitated to form well-developed dendrites in the Dilution Zone. With increasing specific laser energy, the Dilution effect of the Ti-alloy substrate was enhanced, and the microhardness decreased in both the clad and the Dilution Zones. In the TiC+NiCrBSi laser clad layers, TiC particles dissolved into the melted Ni-based alloy (binder material) in the clad Zone. With increasing specific laser energy, the degree of solution of TiC particles was increased. During cooling, fine spherical particles and dendrites of TiC precipitated from the Ni-based alloy. When the TiC volume fraction increased to more than 50%, clustering of TiC particles was observed in the clad Zone. The clustering of TiC particles resulted in a decrease in the homogeneity of the microstructure and microhardness distribution in the clad Zone. The Dilution Zone of the TiC+NiCrBSi clad layers is a mutually melted region of the Ni-based alloy and titanium-alloy substrate and presents a microstructure of dendrites.