Highly Efficient Surface Repairing of AMed Metal Parts by Large-area EB Irradiation

Abstract

In additive manufacturing (AM) processes, three dimensional (3D) objects can be produced by using 3D modelling data. Nowadays, a laser powder bed fusion (LPBF) is becoming popular in AM processes for producing metal parts in the industry field. In general, surface irregularities such as spatter and cavity are generated on the surface. These surface irregularities would lead to increase in surface roughness and reduction in surface fatigue strength. Therefore, surface finishing method is required to repair these surface irregularities. Shot blasting, milling and grinding are typically used for the surface finishing of AMed metal parts. However, these methods have some problems such as remaining of shot grain, tool wear and long processing time.On the other hand, in a large-area electron beam (EB) irradiation method developed recently, high energy density of EB can be obtained without focusing the beam. Therefore, the large-area EB with a diameter of about 60 mm can be used for melting and evaporating material surface instantly, and highly efficient surface finishing of metals such as mold steels and biomaterials was possible. It is expected that the spatter and cavity on the AMed metal parts can be removed in short time by the large-area EB irradiation.In this study, the possibility of surface repairing and surface smoothing for AMed metal parts by large-area EB irradiation is investigated. Then, the mechanism of surface repairing and surface smoothing is also discussed by observation of surface and cross-sectional microstructure. Experimental results show that surface irregularities such as spatter and cavity can be completely repaired in a few minutes by the EB irradiation. Furthermore, bead shape on AMed metal surface is removed with high number of EB irradiation, and surface roughness is significantly decreases. Therefore, surface repairing and surface smoothing for AMed metal parts can be efficiently done by large-area EB irradiation.