Research on Adding Nano-SiC Reinforced Wire Arc Additive Manufacturing Stainless Steel

Because of low cost, high material forming efficiency and utilization, wire arc additive manufacturing (WAAM) is widely used in the manufacture of large components in the past ten years. However, the directional heat dissipation during WAAM stainless steel will cause the growth of coarse columnar grains along the build direction of the components, resulting in strong anisotropy of mechanical properties in WAAM components and reducing its strength. In this paper, nano-SiC grain modifier was added in the WAAM 304 stainless steel to suppress the growth of coarse columnar grains to improve the performance of WAAM components. At first, SiC powder with different particle sizes (100, 300 nm) was made into ethanol-based coatings with mass fractions of 0, 2, 5 and 10 wt.%. During the WAAM process, coating was added layer by layer to make six groups of thin-walled components containing SiC and a group of thin-walled wall components without coating of SiC. Then, microstructure of the components was analyzed through metallographic microscope, X-ray diffraction and scanning electron microscope. The results revealed that the introduction of SiC into the matrix structure promoted heterogeneous nucleation and achieved the effect of grain refinement. As the SiC particle content increased, the matrix grain size further decreased. In addition, mechanical properties and Vickers hardness of the components were tested. The results showed that the ultimate strength and hardness of the SiC-added components were improved, and the anisotropy was reduced. As the SiC content increased, the strength and hardness of the parts increased, which is due to a more refined grain structure.