Browsing by Author "James, William Sean"

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    High‑temperature failure and microstructural investigation of wire‑arc additive manufactured Rene 41
    (Springer, 2023-01-11) James, William Sean; Ganguly, Supriyo; Rodrigues Pardal, Goncalo
    In developing a wire-arc plasma direct energy deposition process for creep-resistant alloys used in high-speed flight applications, structures were built from nickel-based superalloy Rene 41. Samples of additive manufacturing (AM) material were analysed for their microstructural and mechanical properties, in both as-deposited (AD) and heat-treated (HT) conditions. Tensile specimens were tested at room temperature, 538, 760, and 1000 °C. Macroscopically, large columnar grains made up of a typical dendritic structure were observed. Microscopically, significant segregation of heavier elements, grain boundary precipitates, and secondary phases were observed, with key differences observed in HT material. There was a clear distinction between failure modes at different testing temperatures and between AD and HT variants. A fractographic investigation found a progressive move from brittle to ductile fracture with increasing testing temperature in both AD and HT conditions, as well as microstructural features which support this observation.
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    In-process mechanical working of additive manufactured Rene 41
    (American Society of Mechanical Engineers, 2023-01-18) James, William Sean; Ganguly, Supriyo; Pardal, Goncalo
    In developing the wire + arc additive manufacturing (WAAM) process for creep resistant alloys for defence applications, structures were built from nickel-based superalloy Rene 41 (RE41). The performance of the additive manufactured alloy was analysed for applications including components used in high-speed flight environments, where external structures could reach service temperatures of up to 1000 K. As a single use system with relatively short flight times of < 1 hour, components will be highly stressed to minimise structural mass. In this paper, three wall structures were deposited using a plasma transferred arc process, in a layer-by-layer manner where each layer was mechanically worked by machine hammer peening directly after deposition. With a constant impact frequency, three different travel speeds for the peening tool were used for each wall structure. To understand the most effective cold working parameters, samples were tested and analysed for their mechanical properties and microstructural characteristics after aging treatment. Samples were tested at room temperature and compared with results of both non-worked heat-treated AM material and wrought data obtained from literature review.
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    Microstructure and mechanical properties of Inconel 718 and Inconel 625 produced through the wire + arc additive manufacturing process
    (NATO, 2022-03-05) James, William Sean; Ganguly, Supriyo; Pardal, Goncalo
    In developing the wire + arc additive manufacturing (WAAM) process for heat and creep resistant alloys, structures were built from nickel-based superalloys Inconel 718 (IN718) and Inconel 625 (IN625). In this paper, wall structures were deposited in both superalloys, using a plasma transferred arc process. The microstructure was analysed optically and under SEM; both alloys revealed typical dendritic structure with long columnar grains, with little variation between the alloys. The findings suggest that the structures included significant segregation of alloying elements, with potential intermetallic phases e.g. Laves phases and δ-phases also found across the alloys, which showed significantly more segregation of Nb and Mo at the grain boundaries and inter-dendritic regions. The alloys also underwent room temperature mechanical testing, in addition to this IN625 specimens were tested after a solutionising and ageing treatment. Hardness measurements indicated that in general the WAAM process has the effect of increasing material hardness by approximately 10 %, when compared to wrought alloy in a solutionised state. In IN625 the heat-treated specimens showed an increase in hardness of around 6 %, when compared with its as-deposited condition. Elongation in IN625 showed much greater values. Overall, IN718 showed a greater strength with less elongation than IN625. A comparison between both alloys and their stated maximum UTS and YS values from literature revealed that WAAM built IN718 and IN625 in its as-deposited condition can achieve just over half the maximum achievable UTS, with no post-process treatment. The heat-treatment process tested in IN625 marginally reduced the gap in UTS performance by 3.5 %.
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    A performance comparison of additive manufactured creep-resistant superalloys
    (Taylor and Francis, 2023-03-13) James, William Sean; Ganguly, Supriyo; Pardal, Goncalo
    Creep-resistant nickel, cobalt based superalloys, selected for a high-speed flight application, deposited using Wire + Arc Additive Manufacturing (WAAM), was reported. Three different alloys, Haynes 188, Inconel 718, and Rene 41, were deposited, and tested for their high-temperature tensile properties, and the results compared with wrought data. The alloys were tested from ambient temperature to 1000°C in their as-deposited condition and after undergoing industry standard age-hardening and solutionising heat-treatments, to down select the best performing alloy under two different processing conditions. The mechanical strength of the alloys fell short of the maximum achievable in wrought condition. Precipitation-strengthened alloys, Inconel 718 and Rene 41 were found to have underperformed the most significantly, whereas solid-solution-strengthened Haynes 188 suffered the least due to WAAM.
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    Wire + arc additive manufacturing for high-speed flight.
    (2023-01) James, William Sean; Ganguly, Supriyo; Rodrigues Pardal, Goncalo
    The use of Wire + Arc Additive Manufacturing (WAAM) to manufacture high- speed projectiles, such as missiles, is currently an industry challenge due to the nature of high-speed flight and the extreme environment that components are exposed to. Alloys that are suitable for high-speed flight are creep resistant superalloys, this is due to the aggressive heating environment experienced by objects in high-speed flight, and the need for performance at extremely high temperatures. These materials are currently expensive and difficult to manufacture, which is less than ideal for non-recoverable systems such as airborne weapons. The development of missile systems requires flight tests to be affordable and operate in quick succession, to which rapid prototyping offers a significant advantage. The use of traditional manufacturing methods and supply- chain for this purpose are logistically challenging and expensive, mainly due to loss of material though machining. The use of WAAM in a rapid prototyping capability is the driver for this research. To be able to use the process to manufacture and prototype components for high-speed applications, would, if possible, be an excellent solution to reducing the amount of time and money that it currently costs to flight-test and develop these systems. WAAM could also be used for final design production. The effect WAAM route has on the high temperature properties of superalloys is largely unknown. This research is therefore focused on the development of the WAAM process, and selection of alloys suitable for high-speed flight and for WAAM deposition. Four creep-resistant superalloys underwent deposition using a plasma WAAM process and the resulting material was characterised to understand how WAAM affects high temperature performance. The research also investigates post-deposition heat-treatment of these alloys and develops parameters for inter-pass machine hammer peening to improve material performance. The findings from this project increases the understanding between the WAAM process and superalloy strengthening mechanisms and develops a method to increase the performance of additive manufactured material. The most appropriate alloys for both WAAM and the high-speed flight application were ranked and down selected based on their anticipated performance and weldability. The selected alloys then underwent extensive testing from room temperature to 1000 °C, to understand the performance of WAAM built structures at high temperature. The microstructure is examined throughout and found key differences between solid-solution strengthened and age hardened alloys which effects performance. Finally, in-process machine hammer peening was investigated for age hardened Rene 41 and found to greatly increase the performance to match that of the wrought material.