Ultrasonically assisted wire additive manufacturing process and apparatus
The ultrasonically assisted wire additive manufacturing process and apparatus is a new innovation that uses power ultrasound (UA) for benefits in processing molten metals. The UA energy is directly applied in the local deposition pool, which makes this new hybrid process applicable for building parts with any size and geometry.
Additive manufacturing (AM) is the process of 3D printing for industrial use. Instead of countertop devices printing small toys from plastic, industrial AM is used on a much larger scale to create engine blocks, plane components, and many other products made of metal alloys. AM is traditionally done using a powder, where a thin layer of powder is dropped then melted on an X & Y plane using a laser. The powder process is repeated until the part is completed. The excess powder is then disposed of. Wire additive manufacturing (WAM), instead of powder, using a spool of wire and a heat source to melt layers of metal on top each other to form the part. WAM is advantageous over powder manufacturing because of its minimal replacement of subtracting machining, thereby making a better product faster. For example, steel arc-based WAM can achieve a deposition rate of 10kg/hr compared to 600g/hr for powder-based processes.
Although WAM is faster than powder-based processes, WAM shares the same disadvantages when it comes to the solidification microstructure nature of the metal, including coarse columnar grains, porosities, cracks, interdendritic segregation and the lack of strengthening phases. To enhance WAM and make a better product, an innovation is needed to improve the microstructure and accordingly mechanical properties
Researchers at The Ohio State University’s Department of Materials Science and Engineering, led by Dr. Xun Liu, have developed the ultrasonically assisted WAM (UA-WAM) that improves upon the general WAM by process, microstructure, and product quality. The method introduces UA energy from a probe inserted into the local melt pool where it will vibrate at a certain ultrasonic frequency. UA-WAM improves the WAM process by enlarging the processing window and increasing tolerance for welding wire quality. The microstructure of the product is improved by decreasing porosity, suppressing solidification cracking, refining microstructure, and homogenizing element distribution. These improvements result in a higher quality product that can withstand higher mechanical forces. Finally, since the UA probe is inserted directly in the local deposition pool and travels together with the welding torch, there is no restrictions on the size and geometry of the built part by the UA system. Furthermore, the UA energy efficiency is significantly higher than existing practices where UA is indirectly supplied from the building substrate. Industry professionals will be able to use the UA's versatility to achieve the best product that is stronger and more durable than products made with traditional WAM techniques.