Metal transfer and forming behavior of bypass-coupled variable polarity plasma arc additive manufacturing

Abstract

This study proposes a novel bypass-coupled variable-polarity plasma arc additive manufacturing process. This process enables independent control of the main current, bypass current, and their polarities, thereby achieving decoupled control of thermal input to the deposited layers and wire melting. Additionally, the variable polarity effectively removes the oxide film on the surface of aluminum alloys, improving defects in aluminum alloy additive manufacturing. The research results indicate that the bypass-coupled variable-polarity plasma arc additive manufacturing presents different metal transfer forms compared to conventional arc additive manufacturing (MIG/TIG arc heat sources). The droplet transfer behavior manifests in various forms at different wire heights, including droplet transfer, Intermittent bridging transfer, and complete bridging transfer. Notably, the complete bridging transfer results in short metal bridge, which weakens the influence of the coupled arc magnetic field and provides a wider process window for shaping. A detailed analysis of the effects of main and bypass EN/EP currents on the formation morphology reveals that the influence of the main EN current on the width of the deposited layer is twice that of the bypass EN current. By adjusting the main EN current, the remelting depth can be effectively controlled, allowing for precise control over the morphology of the deposited layers. This study demonstrates the potential of this process to enhance deposition efficiency, reduce thermal input, and achieve effective shaping control.