Browsing by Author "Jimenez, Xavier A."

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    Ensuring Melt Track Width Consistency and Crack-Free Conditions Using Interpass-Temperature-Dependent Process Parameters for Wire-Arc-Directed Energy-Deposited Inconel 718
    Jimenez, Xavier A.; Song, Jie; Fu, Yao; To, Albert C. (MDPI, 2024-06-28)
    Melt track width can vary in a wire-arc-directed energy-deposited material (DED) using a constant set of process parameters, leading to a lower-quality build. In this work, a novel framework is proposed that uses the data from the process parameter development stage to create optimized process parameters for a target layer width at different interpass temperatures without hot cracking. Inconel 718 is used as the model material since it is known to suffer from hot cracking during DED processing. In the proposed framework, a process window containing a few sets of process parameters (torch travel speed and wire feed rate) is established for crack-free deposition of Inconel 718, and these parameters are used to create a small database. A linear regression model is then employed to generate interpass-temperature-specific optimized process parameters for a target melt track width. The results demonstrate that the proposed approach can reduce the melt track width variation in the deposited walls from 12% to 3% error on average under different printing conditions. It also demonstrates that interpass temperature (IPT) can be used as a controlled variable and the optimized process parameters as initial values when applying control techniques to the process.
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    Microstructures and Corrosion Properties of Wire Arc Additive Manufactured Copper–Nickel Alloys
    Song, Jie; Jimenez, Xavier A.; To, Albert C.; Fu, Yao (MDPI, 2024-02-14)
    The 70/30 copper–nickel alloy is used mainly in critical parts with more demanding conditions in marine settings. There is a need for innovative methods that offer fast production and cost-effectiveness in order to supplement current copper–nickel alloy manufacturing processes. In this study, we employ wire arc additive manufacturing (WAAM) to fabricate the 70/30 copper–nickel alloy. The as-built microstructure is characterized by columnar grains with prominent dendrites and chemical segregation in the inter-dendritic area. The aspect ratio of the columnar grain increases with increasing travel speed (TS) at the same wire feed speed (WFS). This is in contrast with the equiaxed grain structure, with a more random orientation, of the conventional sample. The sample built with a WFS of 8 m/min, TS of 1000 mm/min, and a track distance of 3.85 mm exhibits superior corrosion properties in the 3.5 wt% NaCl solution when compared with the conventional sample, as evidenced by a higher film resistance and breakdown potential, along with a lower passive current density of the WAAM sample. The corrosion morphology reveals the critical roles played by the nickel element that is unevenly distributed between the dendrite core and inter-dendritic area.