Effects of Post-processing on the Surface Finish, Porosity, Residual Stresses, and Fatigue Performance of Additive Manufactured Metals: A Review

Abstract

Additive manufacturing (AM) has attracted much attention due to its capability in building parts with complex geometries. Unfortunately, AM metals suffer from three major drawbacks, including high porosity, poor surface finish, and tensile residual stresses, all of which will significantly compromise the fatigue performance. These drawbacks present a major obstacle to the application of AM metals in industries that produce fatigue-sensitive components. Many post-processing methods, including heat treatment, hot isotropic pressing, laser shock peening, ultrasonic nanocrystal surface modification, advanced finishing and machining, and laser polishing, have been used to treat AM metals to decrease their porosity, improve the surface finish, and eliminate tensile residual stresses. As a result, significant improvement in fatigue performance has been observed. In this paper, the state of the art in utilizing post-processing techniques to treat AM metals and the effects of these treatments on the porosity, surface finish, and residual stresses of metal components and their resultant fatigue performance are reviewed.

Corrosion fatigue of Ti‐6Al‐4V coupons manufactured by directed energy deposition

“…Surface roughness is a highly influential factor on fatigue life and is subject to large sample‐to‐sample variation. The topics of surface roughness, porosity, and residual stresses have recently been reviewed by Ye et al 7 in a review paper of their effect on the fatigue performance of AM metals. In trying to understand the net effect of such influences on the fatigue life of biomedical components, it is the view of the authors that it is more effective to first study each effect separately, to establish basic relationships between influence and fatigue performance, before seeking to understand the interaction between these independent contributors to fatigue life in genuine biomedical components.…”

“…As titanium alloys are highly reactive with oxygen and nitrogen, their DED processing requires an inert atmosphere (blown inert gas or inert chamber conditions). Post‐processing is usually required to mitigate the effects of such issues as surface finish, microstructure, porosity, and residual stresses in AM components, which have an adverse effect on their long‐term fatigue performance 7 . AM post‐processing for Ti‐6Al‐4V components and their influence on fatigue properties is also discussed in detail by Azarniya et al 9 …”

“…Post-processing is usually required to mitigate the effects of such issues as surface finish, microstructure, porosity, and residual stresses in AM components, which have an adverse effect on their long-term fatigue performance. 7 AM post-processing for Ti-6Al-4V components and their influence on fatigue properties is also discussed in detail by Azarniya et al 9 Quantifying the fatigue performance of DED components and identifying process parameters that can be manipulated to provide improved fatigue performance is critical to achieving effective design and use as medical implants. Shamsaei et al 10 discuss fatigue resistance in Ti-6Al-4V components manufactured by direct laser deposition (DLD), which is an alternate name for DED.…”

Surface Free Energy Dominates the Biological Interactions of Postprocessed Additively Manufactured Ti-6Al-4V

“…Parametric analyses have showed promise on limiting surface defects; nevertheless, surface postprocessing in the form of polishing, passivation, vibratory finish, or sand-blasting is still heavily used in the AM field. , The available literature on AM postprocessing aims to reduce poor surface finish to enhance mechanical strength and fatigue performance. In this regard, all aforementioned techniques have shown their ability to improve the rough as-build surface, R a > 13 μm to micron and submicron values, limiting crack initiation sites . However, relatively few studies have focused on their influence on subsequent eukaryotic cell and microbial attachment of AM surfaces.…”

Numerical predictions of orthogonal cutting–induced residual stress of super alloy Inconel 718 considering dynamic recrystallization

“…The mechanical factor is the material removal process, the thermal factor is the work done by friction, and the chemical factor is the possible reactions caused by cutting fluids [7]. Mechanical effects and plastic deformations of the machining processes change the surface finish and microstructure [8]. Thermal effects are created by the process, causing a change in the dislocation density and distribution and surface integrity [9].…”