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Effects of TiC on the microstructure and properties of TiC/TiAl composite coating prepared by laser cladding
摘要： In order to study the effect of TiC on the microstructure and properties of cladding coatings, TiC/TiAl composite coatings have been prepared by using a laser cladding technique on TiAl alloy, and the microstructure and properties of the resulting composite coatings have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-hardness testing, X-ray stress measurements, friction and wear testing, and an electrochemical workstation. The results showed that when the particle size of TiC is up to micron, the growth of TiC is more developed, the dendrite growth direction is disordered, and the cladding quality is poor. When the particle size of TiC is nanoscale, the morphology of the reinforcement phase TiC is mainly granular and thin rods, which is uniform in the coating and the direction of growth is regular. When the concentration of TiC reaches 20%, the microstructure of the cladding layer grows well and is dense. The microhardness and wear resistance of the coatings prepared by adding nano TiC are better than those of the coatings prepared by micron TiC. When the content of nano TiC in the coatings increases from 10% to 20%, the microhardness and wear resistance of the coatings are obviously improved. The residual stress of the coating is positively related to the crack rate. The residual stress in the coating is tensile stress, and the crack type is the crystal crack in the hot crack. When the particle size of TiC is small and the concentration is high, the coating shows better corrosion resistance.
关键词： TiAl alloy,TiC/TiAl composite coating,Laser cladding,Properties,Microstructure
更新于2025-09-23 15:21:21
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Defect-free Laser Powder Bed Fusion of Ti-48Al-2Cr-2Nb with a high temperature inductive preheating system
摘要： In the industrial panorama, Laser Powder Bed Fusion systems enable the near net shaping of metal powders into complex geometries with unique design features. This makes the technology appealing for many industrial applications, which require high performance materials combined with lightweight design, lattice structures and organic forms. However, many of the alloys that would be ideal for the realisation of these functional components are classified as difficult to weld due to their cracking sensitivity. γ-TiAl alloys are currently processed via Electron Beam Melting to produce components for energy generation applications. The Electron Beam Melting process provides crack-free processing thanks to the preheating stages between layers, but lacks geometrical precision. The use of laser powder bed fusion could provide the means for higher precision, and therefore an easier post-processing stage. However, industrial Laser Powder Bed Fusion systems employ resistive heating elements underneath the base plate which do not commonly reach the high temperatures required for the processing of γ-TiAl alloys. Thus, elevated temperature preheating of the build part and control over the cooling rate after the deposition process is concluded are amongst the features which require further investigations. In this work, the design and implementation of a novel inductive high temperature Laser Powder Bed Fusion system to process Ti-48Al-2Cr-2Nb is presented. Specimens were built with preheating at 800 °C and the cooling rate at the end of the build was controlled at 5 °C/min. Crack formation was suppressed and apparent density in excess of 99 % was achieved.
关键词： High Temperature,Preheating,TiAl,Laser Powder Bed Fusion,Energy generation
更新于2025-09-19 17:13:59
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Cracking behavior and control of β-solidifying Ti-40Al-9V-0.5Y alloy produced by selective laser melting
摘要： A β-solidifying Ti-40Al-9V-0.5Y (at.%) alloy with a high cracking sensitivity has been successfully fabricated by selective laser melting (SLM) in this study. The influence factors for cracking sensitivity, cracking behavior and crack inhibition mechanism were investigated. The results show that the effects of process parameters on cracking sensitivity strongly depend on the cooling rate in molten pool with different heat transfer modes. The conduction mode with higher cooling rates exhibits a higher cracking sensitivity in comparison to the keyhole mode. Microstructure characteristics and phase transformations controlled by cooling rate determine the inherent ductility of β-solidifying γ-TiAl alloys during SLM. On this basis, the formation and inhibition mechanism of solidification and cold cracking are proposed. Finally, the crack-free Ti-40Al-9V-0.5Y sample with fine equiaxed microstructures and favorable mechanical properties (microhardness of 542±19 HV, yield strength of 1871±12 MPa, ultimate strength of 2106±13 MPa and ultimate compressive strain of 10.89±0.57 %) can be produced by SLM. The strengthening mechanism can be attributed to grain refinement and precipitation strengthening.
关键词： Phase transformation,Selective laser melting,Cracking behavior,Microstructure,β-solidifying γ-TiAl alloy,Cracking control
更新于2025-09-16 10:30:52
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Parameter development and characterization of laser metal deposited Ti alloy powders for use at elevated temperatures
摘要： Powder-based laser metal deposition (LMD) of Ti alloys enables the manufacturing of geometrical complex structures with tailored properties for high-temperature applications. The most important parameters for the LMD-process are the laser power, process velocity, laser focus position, gas flow and powder feed rate. Compared to the predominantly used Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo shows a higher oxidation resistance and a lower creep rate. For determining suitable process conditions, a parameter study using Ti-6Al-2Sn-4Zr-2Mo powder is performed. Subsequent, the parameter transfer to a γ-TiAl alloy is examined. The assessment of the dissimilar-LMD-structures is conducted by visual inspection, radiography inspection, microstructural analysis and hardness measurements.
关键词： fiber laser,γ-TiAl,laser metal deposition,microstructure characterization,Ti alloy
更新于2025-09-12 10:27:22
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Laser additive manufacturing of bimetallic structure from Ti-6Al-4V to Ti-48Al-2Cr-2Nb via vanadium interlayer
摘要： As a potential candidate material, Ti6Al4V (TC4) / Ti48Al2Cr2Nb (TiAl) bimetallic structure (BS) material has a good development prospects in the field of aerospace engineering, and has a broad application prospects for the integrated manufacture of aero-engine turbine blades (TiAl) and turbine disks (TC4). However, via the direct bonding of TC4/TiAl BS, it is easy to produce brittle intermetallic compounds which increases the crack sensitivity. Therefore, to a certain extent, the application of TC4/TiAl BS is limited. In this study, we use laser additive manufacturing (LAM) technology to prepare the TC4 / TiAl BS via a V interlayer, which further limits the formation of a brittle phase. The experimental results show that the V interlayer can effectively limit the formation of the brittle phase (Ti3Al), which reduces the crack sensitivity of the formed parts, and forms a good metallurgical joint at the TC4/TiAl BS interfaces. Results of room temperature tensile tests reveal that the tensile strength and elongation of the BS specimens are ~476 MPa, and ~2.8% respectively , which means that the strength of the joint exceeded that of the deposited TiAl alloy without the V interlayer.
关键词： Microstructure,Brittle phases,Ti/TiAl bimetallic structure,Tensile strength,Interfaces,Laser additive manufacturing
更新于2025-09-12 10:27:22