Wire arc additive manufacturing (WAAM) process, which depends on conventional welding arc processes, is a promising option for industries when compared to typical manufacturing processes for assembling large and complicated products. WAAM process attracting manufacturing industries due to its potential to make large and complicated components with real sharp production run time with almost single step process. The process represents greater material savings, higher material buildup rate and speed, cost savings, lower cycle time, less impact on the environment, and capability of producing large size parts when evaluated with other fabrication methods. This paper focuses on WAAM process and reviews some of the common possible process defects found in variety of studies made previously to summaries a guideline for the causes of such defects and provides some prevention methods found by those studies. Of these common possible defects found in researchers works and reviewed in this work are pores, lack of fusion, cracks, and residual stress.

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Burnishing is an advanced finishing process that produces higher-quality surfaces with better hardness and roughness than conventional finishing processes. Herein, a flexible magnetic burnishing brush comprising stainless steel pins under permanent magnet poles was used to investigate the influence of multiple passes and directions on the produced surface of soft and rough ground prepared brass. In total, five different samples were burnished on each of the two brass samples prepared. Four samples were processed in the same direction for up to four passes and the fifth sample was processed with two passes in the opposite direction. Results indicate that there was approximately a 30% increase in hardness and an 83% increase in microroughness for rougher-surface brass samples. For smoothly prepared surfaces, there was approximately a 14% increase in hardness and a 35% increase in microroughness. In the same direction of multi-pass burnishing, increasing the number of passes negatively affected surface roughness; for rougher surfaces, the surface hardness reduced and process uniformity increased owing to surface over-hardening and flaking mechanisms, and for smoother surfaces, the hardness, roughness, and process non-uniformity increased with the number of passes owing to repeated surface deformation at some locations and high flaking at other locations. Compared to single-pass burnishing, wherein the surface roughness and microhardness showed almost no change with high process uniformity, in burnishing with two opposite-direction passes, the produced surface exhibited better surface roughness, process uniformity, and microhardness improvements owing to a reverse strain mechanism. Hence, opposite burnishing passes are recommended.

In this study, four gas tungsten arc welding (GTAW) techniques were employed by varying the travel speed and arc motion to analyze centerline solidification crack resistivity, namely slow (3.6 mm/s), fast (8.4 mm/s), weaving (4.2 mm/s), and tandem side-by-side with alternating working electrodes (3.6 mm/s). Welding high-strength materials like aluminum alloy 2024 (AA 2024) using fusion welding processes may cause centerline solidification cracking due to the wide range of solidification temperatures. AA 2024 was used because of its high susceptibility to centerline solidification cracking; it is mainly used in aerospace industries. This alloy is considered a nonweldable material when fusion welding processes are applied. A GTAW process was used because it has better control over the welding parameters and produces high quality welds. Overall, the tandem technique resulted in thinner axial grain structure surrounded by some equiaxed grains in the weld zone. Moreover, the resistance of centerline solidification cracking was improved by using the tandem technique because of the resulting disordered grain orientation, which reduces crack energy by deflecting the crack path and preventing crack propagation through thickness. In addition, a reduction in the average grain size of 40–60 % was achieved by implementing the tandem technique because of its fast cooling rate. The tandem technique also showed better improvement in microhardness in the weld zone compared to the other three techniques.