Investigation of Cracking Behavior of Fe-6.7 Wt Pct Si Manufactured Using Laser Powder Bed Fusion

The cracking behavior of high-Si steel manufactured using laser powder bed fusion (L-PBF) was investigated. Cracks were classified into three types based on where they formed: (1) cracks formed along the grain boundary, (2) cracks formed along intercellular boundary, and (3) cracks formed along the melt-pool boundary. These cracks appeared in weak areas, such as points of Si segregation or high-angle grain boundaries. L-PBF-manufactured Fe-6.7Si is composed of an A2 phase and brittle B2 and D03-ordered phases under the processing condition of high energy density and low scan speed, showing high cracking susceptibility. During the L-PBF process, residual stress is formed via consequent thermal expansion and shrinkage involved heating and cooling cycles, increasing cracking in vulnerable microstructure regions. The microstructure and crystal structure that directly impact the cracking behavior are determined according to the scanning strategy used during the L-PBF process. The scanning pattern and speed are considered to be the main parameters of this process. A high scanning speed can suppress the formation of brittle B2 and D03 phases by increasing the cooling rate. Strengthening the crystallographic texture through scanning pattern control reduced high-angle grain boundaries, thereby suppressing crack formation. Therefore, this study revealed the possibility of manufacturing crack-free high-Si steel through L-PBF process control.