Simulation-driven development of in-situ alloying Cu-25Cr by electron beam powder bed fusion

Based on its excellent electrical conductivity in combination with a high arc erosion resistance and withstand voltage, the alloy Cu-25Cr is widely applied as a contact material for high-power vacuum interrupters. The utilization of the electron beam powder bed fusion (PBF-EB) method for the processing of this material offers the major advantage of producing extremely fine Cr precipitates due to the rapid solidification of the melt pool, which can further improve the application-specific properties significantly.

In this work, the in-situ alloying of Cu-25Cr from an elemental powder blend via PBF-EB was investigated numerically and experimentally, which resulted in the development of a first process window for the production of dense and well-mixed samples. In doing so, the number of necessary experimental tests could be greatly reduced by using numerical predictions for the definition of the design of experiments. In addition, simulations were used to gain an understanding of the formation mechanism of characteristic defects. These calculations were carried out using an in-house developed software, which was successfully validated against the experimental results.

As part of the experimental tests, it was demonstrated that the powder mixture does not segregate during its application on the start plate, which forms the basis for the reliable production of components with a consistent composition. At a build temperature of approximately 600 °C, it was then possible to produce cuboid samples with a porosity of smaller than 0.1% and a fraction of unmolten Cr particles of smaller than 0.2%.