A review on post processing techniques of additively manufactured metal parts for improving the material properties

Abstract

Metal additive manufacturing (AM) processes are used to produce metal parts with greater design freedom and no material wastage from a CAD model, using powder or wire as feedstock with a layer by layer joining of materials by a high intensity energy source such as laser or electron beam. These processes include selective laser melting (SLM), electron beam melting (EBM) and wire arc additive manufacturing (WAAM) techniques which has wide usage in fabricating metal alloys such as aluminum and titanium for the aerospace and automotive applications. However, these AM parts show many limitations in the as built state like poor surface finish and high tensile residual stress, which will affect the mechanical properties and surface integrity because of the usage of high intensity energy-based melting for the fabrication of parts. This give rise to the need for post processing techniques such as heat treatment and additional machining and polishing operations such as shot peening (SP), laser shock peening (LSP), abrasive flow machining(AFM), friction stir processing (FSP) and hot isostatic pressing (HIP) to improve its surface finish, fatigue life and other material properties. This review paper aims to understand the defects of as built AM parts and focus on the post processing techniques employed by the researchers and its effects on the improvement of AM components.