Flux-Cored Wire for Arc Additive Manufacturing of Alloy Steel: Effect of Inclusion Particles on Microstructure and Properties

Wire and arc additive manufacturing technology is an efficient manufacturing method to realize rapid prototyping of complex parts. Unlike most recent researches which mainly focus on the manufacturing process and equipment, this paper reports the findings of experiments in which the self-developed flux-cored wire is used for arc additive manufacturing of alloy steel. It studies the effects of the contents of inclusions forming elements Ti and Mn on the microstructure and properties of wall parts, and discusses the microstructure evolution in the manufacturing process. It is discovered that the grain size of alloy steel parts manufactured by arc additive is affected by the number of heterogeneous nucleation cores dominated by inclusions in the molten pool, resulting in changed performance of the samples. During the manufacturing process, different sections of the samples experience different thermal cycles. The central region of the sample is heated and tempered, the microstructure change from granular bainite and acicular ferrite into tempered bainite and massive ferrite, and its hardness decrease. Furthermore, the electron backscatter diffraction analysis shows that the thermal cycle makes for the recrystallization in the middle region of the sample, but plasticity of the material does not change. The mechanical properties of the samples do not show obvious anisotropy with decrease in the grain size. Therefore, this study is of particularly significance in developing raw materials for arc additive manufacturing.