Abstract: Electron beam selective melting (EBSM) is an additive manufacturing technology that utilizes an electron beam to build three-dimensional object layer by layer from metal powder, and can be applied in manufacturing aerospace components and medical implants. Effect of the single-pass scanning with constant power on the top surface topography is studied by using the 316L stainless steel powder material. It’s found that the ratio of the electron beam power P to the scanning velocity v is the key factor affecting the top surface topography. With the increase of P/v, the top surface topography changes to a gully type from a balling-net type, and the spatters increase. The evolution of the top surface topography with the increase of the fabricated height is also studied. And it’s found that the topography worsens with the increase of the fabricated height. The reasons for the topography worsening are explained in detail. A multi-pass scanning process with progressively increasing power is developed, and it largely improves the top surface topography of the fabricated parts. The roughness Ra of the top surface is lower than 8 μm. Uniform and fine microstructures can be obtained, and the relative density of the fabricated sample reaches up to 99.96%. Compared to the single-pass process, the multi-pass process does not cause additional melting loss of the elements.

Key words: additive manufacturing, electron beam, scanning method, selective melting, surface topography, Abrasive belt, Contact, Rail grinding, Simulation