A lexis Renaud

Abstract

The fatigue behavior of additively manufactured (AM) parts is strongly affected by manufacturing parameters. In the case of laser powder bed fusion (LPBF) processes, the characteristics of the powder and of the laser beam lead to specific properties and microstructures. The surface of AM parts is characterized by a very high roughness, a high number of macroscopic pores compared to the bulk, and by the presence of partially melted particles and residual powder trapped into the roughness profile. These elements have significant impact on the fatigue behavior of the parts.

Several post-processing treatments can improve the surface quality of AM parts and decrease their roughness. These processes can be chemical (chemical polishing), electrochemical (electrolytic polishing or plasma electrolytic polishing), physical (laser finishing) or mechanical (tribological processes, machining). They all affect the metallic surface in different ways and may impact the final properties such as the fatigue resistance.

In the scope of the After-ALM and the NEMO projects, the above-listed treatments were applied on 316L stainless steel and Inconel 718 alloys manufactured by LPBF. The resulting surface morphologies and microstructures were characterized, and the fatigue behavior of the treated materials was evaluated using rotating bending tests according to aeronautical standards. The fracture surfaces were investigated to understand the initiation mechanisms for the different post-processing treatments. Comparison of the effect of roughness and internal stresses were undertaken to separate the influence of these two effects.

Session