Reviewing Post-Processing Techniques to Enhance Mechanical Properties of Parts Fabricated Using WAAM
Authors: Abdallah Said , Pervaiz Salman 
Published: January 2022

Abstract
The different additive manufacturing (AM) technologies are showing a higher flexibility and process capabilities over the years, these technologies are not limited to produce a prototype only, but also to produce a valuable and cost-effective large near net parts. The Wire Arc Additive Manufacturing (WAAM) technique is regarded as one of the most important technologies for producing a metallic component. As it becomes one of the most interesting technology in the industrial sector, it can provide an unlimited printing size based on the used mechanism range. In this study, different microstructure deformation-based post processing methods have been discussed, some of them could be performed in-process (during) or even post-process (after) the WAAM technique. This study will focus more on the rolling deformation method comparing with the other post-processing techniques. Rolling process is observed as a good choice for post processing that can be used to improve the material microstructure features. Moreover, the parameters such as roller radius, applied load, the WAAM torch angle and the distance between the pressing side of the roller and the welding point show controlling influence on the internal grain features and on the surface waviness. surface roughness is termed as one of the main problems on the produce parts using WAAM technology. This study discussed different ways by which the internal residual stresses can be reduced, and mechanical properties of fabricated parts can be improved. Some studies revealed that hot forging can be used as a post processing technique after the WAAM process. Utilization of hot forging after the WAAM process shows an immediate positive effect on the produced sample by improving both of yield and ultimate strengths of the part. Furthermore, some other studies show that the forging significantly reduce the porosity due to the applied hot forging, as it is showing a higher effect with increasing the hammering force and vice versa. Also, some studies utilized rolling process as a post processing technique. So, the current study compared hot forging with the results extracted from the rolling deformation.
This study aims to review the post processing techniques such as rolling process and hot forging process. The study provides understanding about the selection of the parameters to end up with a higher quality and tougher workpiece material. A comprehensive review on many rolling methods and directions during and after the WAAM process are discussed in detail. The main feature of this study is to provide a thorough understanding of the start-of-the-art involved in WAAM post processing. The study also revealed research gaps by comparing the existing literatures and adding a complete comparison and conclusions for each part which could be taken as potential in the future research topics for researchers in the same field. At the end, the manuscript has discussed the different post-processing design considerations that assure the best and the higher precision deposited part.