Study on Single-Layer and Single-Channel Microstructure of 304 Stainless Steel Using Joule Heat Additive Manufacturing

In this study, a solution to the issue of a large heat-affected zone in Wire Arc Additive Manufacturing is presented by employing the Joule Heat Additive Manufacturing method to create a single layer and single channel with a reduced heat-affected zone. The microstructure of the single layer and single channel is thoroughly investigated using various detection methods, including optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). The results reveal that the heat-affected zone formed by the Joule Heat Additive Manufacturing method is smaller than that produced by the Wire Arc Additive Manufacturing method. Additionally, the grains in the single layer and single channel progress from planar to columnar, then equiaxed, and finally back to columnar from the fusion line to the top of the wire. The element content and distribution are relatively uniform. The microstructure of the single layer consists of austenite and a small amount of ferrite, with austenite accounting for 99.71% of the content. The grain size in the middle of the wire is mainly around 10 μm, with the smallest angle grain boundaries within 10°. The distribution of local grain orientation differences in the three regions is found to be largely consistent. The analysis of the microstructure of the single layer and single channel serves as a valuable reference for understanding the behavior of single-channel multi-layers in future studies.