In-situ observation of process instabilities during selective laser melting of metallic powder

Abstract

Additive manufacturing processes, derived from rapid prototyping, are currently in industrial growth. Those processes are very attractive due to the fact that they allow manufacturing parts in a large range of materials with very complex shapes directly from the Computer-Aided Design (CAD) file. Aircraft and aerospace industries are greatly interested by the flexibility, the reactivity and the possibilities offered by additive manufacturing processes, such as topological optimization or new ways of design which can allow building one single part instead of welding several parts obtained by more conventional processes. However, those technologies are relatively recent and are not perfectly under control.Selective laser melting (SLM) process consists in melting one powder layer under scanning laser and spreading another powder layer in order to build the part layer by layer. This process is naturally unstable involving changes of state (solid/liquid and sometimes liquid/vapor) in a short time (about some milliseconds). The presence of defects inside SLM parts can greatly influence their mechanical properties. So, it is necessary to monitor the melt pool and its environment during the manufacturing of parts in order to preserve a traceability of their defects. A system of coaxial visualization of the melt pool from an industrial machine was developed and some process instabilities could be observed.Additive manufacturing processes, derived from rapid prototyping, are currently in industrial growth. Those processes are very attractive due to the fact that they allow manufacturing parts in a large range of materials with very complex shapes directly from the Computer-Aided Design (CAD) file. Aircraft and aerospace industries are greatly interested by the flexibility, the reactivity and the possibilities offered by additive manufacturing processes, such as topological optimization or new ways of design which can allow building one single part instead of welding several parts obtained by more conventional processes. However, those technologies are relatively recent and are not perfectly under control.Selective laser melting (SLM) process consists in melting one powder layer under scanning laser and spreading another powder layer in order to build the part layer by layer. This process is naturally unstable involving changes of state (solid/liquid and sometimes liquid/vapor) in a short time (about some mi...