Effects of Ultrasonic Micro-forging on 304 Stainless Steel Fabricated by WAAM

304 stainless steel parts of single pass were fabricated by wire and arc additive manufacturing using gas tungsten arc welding (TIG) and ultrasonic micro-forging. The microstructure and microhardness were studied at different powers of ultrasonic micro-forging. The relationship between microhardness and power of ultrasonic micro-forging was established. It was found that the parts were well formed and no defects such as micro-cracks or pores were observed. Different thermal histories resulted in various microstructures. The microstructure of parts was fined by the treatment of ultrasonic micro-forging. The microhardness of the parts was also enhanced by the treatment of ultrasonic micro-forging while declined from the top to the bottom of the fabrications. When the power of ultrasonic micro-forging was fixed at 1000 W, the depth of action from ultrasonic micro-forging comes to about 1 mm and the maximum of microhardness reached to 350 HV0.1.