Additive manufacturing of Ti6Al4V parts using ultrasonic assisted direct energy deposition

Abstract

Directed energy deposition (DED) parts are generated via concentrated energy source by melting powder during layer by layer deposition. The size of grains in structure built parts is determined by the parameters in the DED process. In contrast, the size of grains in structure deposited metal parts is dependent on the mechanical properties. A fundamentally new method of ultrasonic assisted direct energy deposition (UDED) changes the structure of metal of a Ti6Al4V alloy. Varying the frequency and power of ultrasonic vibrations affects the region of interaction of the powder and the laser spot. It is possible to purposefully obtain parts with a uniform or, if necessary, a gradient structure, depending on the requirements. Systematic investigations of the structure were conducted for various frequencies and power levels of ultrasonic vibrations during DED of Ti6Al4V parts. Wear tests at high loads showed that the coefficient of friction parts obtained by UDED were lower than those obtained by DED. These results were related to the fine grain structure and increased microhardness. Load cycling resistance of tested specimens obtained by UDED was twice as high as those obtained by DED. Irregular needles and fine grains of specimens from UDED also indicated that the structure was resistant to cracks.