Showing papers on "Titanium powder published in 2017"

Cold Spraying of Armstrong Process Titanium Powder for Additive Manufacturing

Abstract: Titanium parts are ideally suited for aerospace applications due to their unique combination of high specific strength and excellent corrosion resistance. However, titanium as bulk material is expensive and challenging/costly to machine. Production of complex titanium parts through additive manufacturing looks promising, but there are still many barriers to overcome before reaching mainstream commercialization. The cold gas dynamic spraying process offers the potential for additive manufacturing of large titanium parts due to its reduced reactive environment, its simplicity to operate, and the high deposition rates it offers. A few challenges are to be addressed before the additive manufacturing potential of titanium by cold gas dynamic spraying can be reached. In particular, it is known that titanium is easy to deposit by cold gas dynamic spraying, but the deposits produced are usually porous when nitrogen is used as the carrier gas. In this work, a method to manufacture low-porosity titanium components at high deposition efficiencies is revealed. The components are produced by combining low-pressure cold spray using nitrogen as the carrier gas with low-cost titanium powder produced using the Armstrong process. The microstructure and mechanical properties of additive manufactured titanium components are investigated.

Mechanical behavior and microstructure properties of titanium powder consolidated by high-pressure torsion

Abstract: Research was conducted to investigate the potential for consolidating titanium powder using high-pressure torsion (HPT) at room temperature. The nanostructured samples processed by HPT were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show there is a significant refinement of the Ti powder and it consolidates into bulk nanostructured titanium with a mean grain size estimated by TEM as ~200–300 nm and a mean crystallite size measured by XRD as ~20–30 nm. Microhardness measurements and tensile testing show high strength and low ductility after consolidation under a pressure of 6.0 GPa for 5 revolutions. Additional short annealing at a temperature of 300 °C for 10 min leads to a significant enhancement in ductility while maintaining the high strength.

Surface chemistry of the titanium powder studied by XPS using internal standard reference

Abstract: Surface chemistry of the titanium powder has particularly growing interest due to the increasing application of titanium components prepared by powder metallurgy, in particular metal injection moulding and additive manufacturing. Due to the high chemical activity, number of titanium oxides, calcium and complex Ca–Ti–oxides can be expected on the component/medical implant surface, depending on powder and component manufacturing and post-treatment, but are very difficult to analyse due to the lack of the experimental data and analysis methodology. Therefore, a methodology for the analysis of the surface chemistry of the Ti-powder by XPS utilising internal standard reference was developed. The obtained methodology was used for the surface analysis of titanium powder and identification of its surface oxide composition. The results show that the powder surface is covered by TiO2 layer in the form of rutile with a thickness of 4.4 nm. Carbon and nitrogen impurities were also found present on the powder ...

Hydrogen Assisted Magnesiothermic Reduction (HAMR) of Commercial TiO2 to Produce Titanium Powder with Controlled Morphology and Particle Size

Abstract: A two-step thermochemical reduction was developed to remove oxygen from commercial titanium dioxide, TiO2, producing metallic titanium powder. The rst step was to remove >95% of the oxygen by Mg reduction in a hydrogen atmosphere, followed by a de-oxygenation step. The goal is to produce Ti powder that meets the standard speci cations for titanium. Several ancillary steps including granulation and heat treatment were introduced to modify the powder morphology, particle size and powder density to make the powder suitable for a range of applications. Detailed compositional analysis indicated that the nal product meets the ASTM B299 for general-purpose titanium sponge. The powder can be irregularly shaped or spherical with different granulation treatments. [doi:10.2320/matertrans.MK201628]

Thermodynamic behaviour and formation mechanism of novel titanium carbide dendritic crystals within a molten pool of selective laser melting TiC/Ti–Ni composites

Abstract: Selective laser melting (SLM) was applied to prepare TiC/Ti–Ni composites by using a mixed powder composed of titanium powder, nickel powder and titanium carbide powder. The result indicated that fine TiC particles were transformed into in situ Ti6C3.75 dendrites based on the complete melting mechanism and coarse TiC particles just partly experienced melting to form epitaxial dendrites along the margin of the remaining TiC particles. Besides, laser scan speed was found to have a significant influence on Ti6C3.75 dendrite growth. To give a better insight into the thermodynamic behaviour of TiC within the mesoscopic molten pool which was difficult to be monitored by experimental methods, a numerical simulation method was used. Due to the existence of differences in thermal conductivity between TiC and the matrix, reverse thermal hysteresis within TiC particles was predicted, influencing the temperature and its gradient on the TiC particles. Furthermore, the melting mechanism of TiC particles and growth processes of Ti6C3.75 dendrites were discussed. Moreover, nanoindentation load–penetration depth curves were also measured, reaching a value of 6.84 GPa at the applied v of 350 mm s−1.

Finite element simulations of temperature distribution and of densification of a titanium powder during metal laser sintering

Abstract: Metal Laser Sintering (LS) is a powder bed fusion process that can be used to produce manufactured parts of complex shapes directly from metallic powders. One of the major problems of such powder bed fusion processes is that during the continuous movement of the laser beam, temperature distribution becomes inhomogeneous and instable in the powder. It leads to greater residual stresses in the solidified layer. Thus, temperature analyses must be performed to better understand the heating-cooling process of the powder bed as well as the interactions of different laser scanning paths within a sintering pattern. A transient 3D Finite Element (FE) model of the LS process has been developed with the commercial FE code ABAQUS. The model takes into account the different physical phenomena involved in this powder bed fusion technology (including thermal conduction, radiation and convection). A moving thermal source, modeling the laser scan, is implemented with the user scripting subroutine DFLUX in this FE code. The material’s thermal behavior is also defined via the subroutine UMATHT. As the material properties change due to the powder bed fusion process, the model takes it into account. In this way, the calculation of a temperature-dependent behavior is undertaken for the packed powder bed, within its effective thermal conductivity and specific heat. Furthermore, the model accounts for the latent heat due to phase change of the metal powder. Finally, a time- and temperature-dependent formulation for the material’s density is also computed, which is then integrated along with the other thermal properties in the heat equation. FE simulations have been applied to the case of titanium powder and show predictions in good agreement with experimental results. The effects of process parameters on the temperature and on the density distribution are also presented.

Electric spark ignition sensitivity of nano and micro Ti powder layers in the presence of inert nano TiO 2 powder

Abstract: Metallic dust clouds have proven to be explosive even when mixed with high percentages of inert solids. In this paper, fire hazard of metallic dust layers was investigated as a potential ignition source. The minimum ignition energy and flame spread velocity of layered Ti powder mixed with different percentages of TiO 2 were determined using electric spark ignition. The results indicated that MIE of dust layers (MIEL) was far larger than that of dust clouds (MIEC) for Ti powder and its solid mixtures, likely due to a different ignition mechanism. As expected, MIEL of nano Ti powder was much lower than that of micro Ti powder. Once ignited, flame spread velocity of nano Ti powder layer reached 625 mm/s, a value far larger than the 5 mm/s for micro Ti powder.

Method for additive manufacturing

Abstract: A method comprising the steps of: distributing a titanium alloy or pure titanium powder layer on a work table inside a vacuum chamber, directing at least one electron beam from at least one electron beam source over the work table causing the powder layer to fuse in selected locations, distributing a second powder layer on the work table of a titanium alloy or pure titanium inside the build chamber, directing the at least one electron beam over the work table causing the second powder layer to fuse in selected locations, and releasing a predefined concentration of the gas from the metal powder into the vacuum chamber when at least one of heating or fusing the metal powder layer, wherein at least one gas comprising hydrogen is absorbed into or chemically bonded to the titanium or titanium alloy powder to a concentration of 0.01-0.5% by weight of the hydrogen.

Aqueous Synthesis of Technetium-Doped Titanium Dioxide by Direct Oxidation of Titanium Powder, a Precursor for Ceramic Nuclear Waste Forms

Abstract: Technetium-99 (Tc) is a problematic fission product that complicates the long-term disposal of nuclear waste due to its long half-life, high fission yield, and the environmental mobility of pertechnetate, its stable form in aerobic environments. One approach to preventing Tc contamination is through incorporation into durable waste forms based on weathering-resistant minerals such as rutile (titanium dioxide). Here, the incorporation of technetium into titanium dioxide by means of simple, aqueous chemistry – direct oxidation of titanium powder in the presence of ammonium fluoride -- is achieved. X-ray absorption fine structure spectroscopy and diffuse reflectance spectroscopy indicate that Tc(IV) replaces Ti(IV) within the structure. Rather than being incorporated as isolated Tc(IV) ions, Tc is present as pairs of edge-sharing Tc(IV) octahedra similar to molecular Tc(IV) complexes such as [(H2EDTA)TcIV](μ−O)2. Technetium-doped TiO2 was suspended in deionized water under aerobic conditions, and the Tc leac...

Titanium Powder Sintering in a Graphite Furnace and Mechanical Properties of Sintered Parts

Abstract: Recent accreditation of titanium powder products for commercial aircraft applications marks a milestone in titanium powder metallurgy. Currently, powder metallurgical titanium production primarily relies on vacuum sintering. This work reported on the feasibility of powder sintering in a non-vacuum furnace and the tensile properties of the as-sintered Ti. Specifically, we investigated atmospheric sintering of commercially pure (C.P.) titanium in a graphite furnace backfilled with argon and studied the effects of common contaminants (C, O, N) on sintering densification of titanium. It is found that on the surface of the as-sintered titanium, a severely contaminated porous scale was formed and identified as titanium oxycarbonitride. Despite the porous surface, the sintered density in the sample interiors increased with increasing sintering temperature and holding time. Tensile specimens cut from different positions within a large sintered cylinder reveal different tensile properties, strongly dependent on the impurity level mainly carbon and oxygen. Depending on where the specimen is taken from the sintered compact, ultimate tensile strength varied from 300 to 580 MPa. An average tensile elongation of 5% to 7% was observed. Largely depending on the interstitial contents, the fracture modes from typical brittle intergranular fracture to typical ductile fracture.

Plasma atomization method and apparatus for preparing pure titanium or titanium alloy powder

Abstract: The invention relates to a plasma atomization method and apparatus for preparing spherical pure titanium or titanium alloy powder, and belongs to the technical field of preparation of titanium or titanium alloy powder. The plasma atomization method for preparing pure titanium or titanium alloy powder comprises the following steps of (1) preparing a titanium wire or titanium alloy wire with the diameter ranging from 3 millimeters to 20 millimeters, (2) using a plasma torch to fuse and atomize the titanium wire or titanium alloy wire in an atomization bin with an argon atmosphere to obtain atomized pure titanium particles or titanium alloy particles, and (3) feeding argon flow with the temperature ranging from 300 DEG C to 500 DEG C into the atomization bin, carrying out laminar cooling on the atomized pure titanium particles or titanium alloy particles to obtain pure titanium or titanium alloy powder. The obtained powder is good in degree of sphericity and low in the content of satellite balls, and has the advantages of being uniform in size distribution, high in purity and degree of sphericity, good in liquidity, low in oxygen content and impurity content, free of bond or cluster phenomenon and the like. The prepared titanium powder can be widely applied to the forming manners such as metal additive manufacturing, powder injection moulding and hot isostatic pressing for manufacturing parts with high precision.

Wear-resistant flux-cored wire for stainless steel

Abstract: The invention discloses a wear-resistant flux-cored wire for stainless steel. The wear-resistant flux-cored wire consists of a flux core and a stainless steel sheath coating the outer side of the flux core, wherein the flux core comprises the following raw materials in parts by weight: 15-22 parts of chromium powder, 1-4 parts of titanium powder, 0.5-2 parts of nickel powder, 1-4 parts of silicon calcium alloy, 1-4 parts of magnalium, 4.5-7 parts of ferromanganese, 2-5 parts of ferromolybdenum, 2-4 parts of ferrocolumbium, 4-8 parts of rare earth ferroalloy, 4-8 parts of vanadium-nitrogen alloy, 6-9 parts of carbonate, 3-6 parts of graphite and 100-150 parts of iron powder. The wear-resistant flux-cored wire for stainless steel has favorable wear resistance, corrosion resistance, heat resistance and mechanical property; a deposited metal structure is compact, pore-free and crack-free; and the wear-resistant flux-cored wire for stainless steel can be favorably combined with a base material and is stable in performance.

Temperature profile and melt depth in laser powder bed fusion of Ti-6Al-4V titanium alloy

Abstract: In this paper, the prediction of temperature profile and melt depth for laser powder bed fusion (L-PBF) of Ti-6Al-4V titanium powder material was performed by numerically solving the heat conduction-diffusion equation using a finite difference method. A review of the literature in numerical modeling for laser-based additive metal manufacturing is presented. Initially, the temperature profile along the depth direction into the powder material is calculated for a stationary single pulse laser heat source to understand the transient behavior of the temperature rise during L-PBF. The effect of varying laser pulse energy, average power, and the powder material’s density is analyzed. A method to calculate and predict the maximum depth at which localized melting of the powder material occurs is provided.

Characterization and Sintering of Armstrong Process Titanium Powder

Abstract: Titanium and titanium alloys have a high strength to weight ratio and good corrosion resistance but also need longer time and have a higher cost on machining. Powder metallurgy offers a viable approach to produce near net-shape complex components with little or no machining. The Armstrong titanium powders are produced by direct reduction of TiCl4 vapor with liquid sodium, a process which has a relatively low cost. This paper presents a systematic research on powder characterization, mechanical properties, and sintering behavior and of Armstrong process powder metallurgy, and also discusses the sodium issue, and the advantages and disadvantages of Armstrong process powders.

Microstructural Evolution during Pressureless Sintering of Blended Elemental Ti-Al-V-Fe Titanium Alloys from Fine Hydrogenated-Dehydrogenated Titanium Powder

Abstract: A comprehensive study was conducted on microstructural evolution of sintered Ti-Al-V-Fe titanium alloys utilizing very fine hydrogenation-dehydrogenation (HDH) titanium powder with a median particle size of 8.84 μm. Both micropores (5–15 μm) and macropores (50–200 μm) were identified in sintered titanium alloys. Spherical micropores were observed in Ti-6Al-4V sintered with fine Ti at the lowest temperature of 1150 °C. The addition of iron can help reduce microporosity and improve microstructural and compositional homogenization. A theoretical calculation of evaporation based on the Miedema model and Langmuir equation indicates that the evaporation of aluminum could be responsible for the formation of the macropores. Although reasonable densification was achieved at low sintering temperatures (93–96% relative density) the samples had poor mechanical properties due mainly to the presence of the macroporosity and the high inherent oxygen content in the as-received fine powders.

The Effect of Charge Component Composition on the Structure and Properties of Titanium Matrix Sintered Composites with High-Modulus Compounds

Abstract: The effect of the powder matrix base (Ti and TiH2) and the type of reinforcing additives (5 wt.% TiC, TiB2, B, and B4C) on the structurization features and some properties of metallic matrix composites sintered hereof is investigated. It is shown that the application of titanium hydride powder with TiC and TiB2 additives as the starting powder base allows obtaining sintered materials with lower porosity (≤2%) and higher hardness, compared to the composites produced based on commercial titanium powder. The microstructure of sintered composites considerably depends on the type of reinforcing additives. TiC particles hardly interact with the matrix phase and they are relatively equilibrium, while the TiB inclusions (as it is in the case of TiB2 additive) are acicular 1–5 μm in dia. and 10–25 μm long. The microstructure of the composites sintered from the mixture of titanium hydride and boron carbide powders has conglomerates 20–50 μm in size, consisting of highly dispersed acicular particles of titanium boride phases and unimportant number of TiC equilibrium particles.

Preparation method and application of graphene composite material

Abstract: The invention belongs to the technical field of graphene composite materials, in particular to a preparation method and application of a graphene composite material The preparation method of the graphene composite material comprises the following steps that a substrate powder body is placed into a plasma gaseous phase deposition device, under a vacuum environment, working gas is led into a plasma generation area to enable a carbon source to be loaded into the plasma generation area, and three-dimensional graphene is obtained on the surface of a metal powder body within 01-1 hour; and the substrate powder body is the metal powder body or a nonmetal powder body, the metal powder body comprises one or more of aluminum powder, nickel powder, copper powder and titanium powder, and the nonmetal powder body comprises one or more of silicon carbide powder and quartz According to the method, the graphene can be directly prepared on a metal powder body substrate or a nonmetal powder body substrate, no complex pre-treatment technology and high-temperature process is needed, and the treatment working procedure is more simplified and has compatibility; and a concise method is provided for preparation of a carbon-coated composite material, and the preparation method is suitable for large-scale production

Fabrication of TiB2/Al composite by melt-SHS process with different content of titanium powder

Abstract: Melt-SHS (self-propagating high-temperature synthesis), based on the SHS process and oxide reaction method, was used for preparation of TiB2/Al composites. The mass ratio of two reactants, Ti powder/TiO2, in initial powder mixture was varied from 0:1 to 1:0. The results showed that the 5 wt% TiB2/Al composites could be successfully produced by a reaction of aluminum powder, TiO2, and B2O3 in Al melt at 950 °C, while the reaction rate was slow. The addition of titanium powder helps to reduce the content of Al2O3 and destroy the coating structure of Al2O3 covered TiB2 particles, which leads to the acceleration of reaction process and improvement of particle concentration. A significant improvement was that TiB2 particles were dispersively distributed when the mass ratio of Ti powder/TiO2 was 2:3. As a result, the 5 wt% TiB2/Al composites fabricated by melt-SHS process with modified reactants ratio showed excellent tensile properties with the ultimate tensile strength as high as 114.24 MPa. Besides, the composite also showed superior ductility.

Effects of SiC Nanoparticles on the Properties of Titanium-Matrix Foams Processed by Powder Metallurgy

Abstract: Metal-matrix foams are used widely for structural applications such as impact energy absorption, vibration resistance and weight reduction. In this study titanium nanocomposite foams with different porosity percentages were produced using TiH2, as foaming agent, by powder metallurgy technique. At first, raw materials including titanium powder and different weight percentages of SiC nanoparticles were mixed and then different amounts of TiH2 were added to the mixture. The mixture was compacted at 200 MPa. The samples were heat treated in two stages, first at 400 °C for 1 h, as a partial sintering, and then at 1050 °C for 2 h, as foaming treatment. Mechanical and structural properties such as compressive strength, energy absorption, porosity percentage and relative density of samples were measured and compared together. Thermo gravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed on foaming agent and samples. The results showed uniform distribution of SiC nanoparticles in titanium matrix and also homogenous pore structure. It was concluded that with increasing SiC weight percent, relative density is increased to 0.43 in the sample with 1.5 wt % SiC. Besides, the measured compressive strength of samples was in the range of 14.4–32.3 MPa. Moreover, it was concluded that the energy absorption of samples increases with increasing SiC nano particles up to 33.09 MJ/m3.

Evaluation of the α-Case with TiO 2 in Mold for Titanium Investment Casting

Abstract: Molten titanium easily reacts with not only oxygen, carbon, and nitrogen but also the ceramic mold to form an α-case on the casting surface. However, the brittle α-case must be removed by chemical milling because it weakens the mechanical properties of the casting. The aim of this study is to evaluate and suppress the formation of the α-case by including TiO2 in the mold. Titanium powder was added into the alumina mold in order to facilitate the formation of TiO2 by the oxidation of titanium during mold firing. Another way to include TiO2 in the mold was to simply add TiO2 into the alumina mold. Optical microscopy and the micro-Vickers hardness test were used to characterize the α-case. The composition and morphology of the molds were confirmed using X-ray diffraction and field emission scanning electron microscopy. The mold with added titanium (Al2O3 + Ti) was effective in controlling the α-case. However, the interfacial reactions of the mold with the added TiO2 (Al2O3 + TiO2) exhibited distinct differences in α-case formation compared to the Ti-added mold (Al2O3 + Ti), while having almost identical compositions.