Browsing by Subject "Superalloys"

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Direct Selective Laser Sintering of Superalloys
(2002) Klocke, Fritz; Wagner, Christian
The advantages of powder metallurgy lie within the large degree of freedom for material design and thus is especially used in the production of high performance parts. Layer manufacturing is an appropriate method to produce complex parts rapidly. Direct Selective Laser Sintering (SLS) presents a technology which combines both benefits. Therefore many efforts are done today to qualify new materials for SLS [DAS 98, MEI 99, OVE 01, WOL 00]. Particulary materials, which are hard to cut, to cast or to shape in any else matter, are of interest. In the presented paper investigation results on Selective Laser Sintering of metals are shown on the basis of the nickel base alloy INCONEL™ 718. First, a process model has been created to discribe the mechanisms of SLS of metals. On the base of the model, process simulations and experimental investigations have been performed. In some cases, affiliating a heat treatment after the laser sintering step is favorably to improve the metallic structure and thus has also been tested. Finally, the metallograhic structures and mechanical properties were analysed.
Implementation of a high-fidelity axisymmetric model in a Vacuum Arc Remelting process
(2011-05) Lopez, Luis Felipe; Beaman, Joseph J.; Williamson, Rodney L.
Vacuum Arc Remelting (VAR) is a secondary process used for homogenization of high-melting-point and oxygen-sensitive materials such as superalloys and titanium alloys. The VAR process is carried out with the aim of melting a large consumable electrode in such a way that the resulting ingot has improved homogeneity. The Specialty Metals Processing Consortium (SMPC) has spent the past 20 years developing technology to improve control over the final ingot remelting and solidification processes to alleviate conditions that lead to the formation of inclusions and segregation. Channel segregates are concentration defects arising during the solidification of large-diameter solute-rich alloys. As manufacturers for turbine engines and generators call for larger ingots, it becomes more difficult to produce them without these defects. If, however, liquid pool depth can be controlled precisely to stabilize the solidification zone in the ingot, we could, in principle, produce larger ingots that are defect free. A problem arises because measurements obtained from the VAR furnace do not give enough information to accurately estimate the liquid pool shape in dynamic melting situations. Also, the solidification process in VAR is extremely complex due to the multiple physical domains present and a high-fidelity model is required to give an accurate description of the dynamic process. The Basic Axisymmetric Remelting (BAR) code was initially developed by Lee Bertram at Sandia National Laboratories as a high-fidelity multi-energy model to describe ingot casting in this system. In this work we present a new strategy to improve the accuracy of the estimates used in the control system. This strategy consists of implementing BAR as a new set of measurements to be used by the estimator. This new strategy was used in tests jointly sponsored by SMPC and Los Alamos National Laboratory (LANL) in February 2011 using a laboratory-scale furnace and alloy 718 electrodes.