Analysis of external and internal defects of molybdenum deposited via wire arc additive manufacturing

Molybdenum is an essential high-temperature structural material but has poor processability. Additive manufacturing provides a new way to fabricate molybdenum. In this work, wire arc additive manufacturing (WAAM) was adopted, and the frequency is the parameter to be studied. As the frequency increases, the diameter of the sample increased logarithmically, and the external outline of the sample fluctuated violently. Simultaneously, the growth direction of internal defects becomes more and more vertical, indicating that the morphology of the solid-liquid interface of the molten pool is changing with frequency. The cavity growth in the center from the bottom to the top under the condition of 20 Hz, indicating that the center of the molten pool has always maintained an extremely high temperature, causing the molten metal to continue to vaporize. The study of frequency parameters contributes to the development of WAAM, and deepens the understanding of the molten pool dynamics of the manufacturing process.