Surface roughness evolution of 1Cr12Ni3MoVN alloy prepared by additive/ subtractive hybrid manufacturing

To improve the surface quality of samples manufactured by directed energy deposition (DED), the subtractive process is integrated with additive manufacturing, a method known as additive/subtractive hybrid manufacturing (ASHM). The correlation between the surface quality of the subtractive process and the process parameters of additive manufacturing has been established in this work. The results demonstrate that a high linear energy density can improve the surface quality of the subtractive process. To comprehensively analyze the mechanisms, field emission scanning electron microscopy and nanoindentation are employed to investigate the microstructure and mechanical behavior of the ASHMed specimens. It is observed that increasing linear energy density can strengthen the tempering effect on the previously deposited layer, thereby promoting the precipitation of M2C (M=Mo) carbides along the grain boundary and reducing defects at the grain boundary. Furthermore, this enhancement reinforces the grain boundary strength, leading to a transition in the fracture mechanism from intergranular to transgranular fracture during the subtractive process. As a result, the surface roughness of ASHMed samples improves with increasing linear energy density. Additionally, the finite element simulation of the ASHM process was performed, demonstrating a close correspondence with experimental results, with an error margin of 6.30 %. In conclusion, the model described in this paper can predict the surface quality of the 1Cr12Ni3MoVN alloy fabricated by the ASHM.