Surface Finishing of Additive Manufactured Ti-6Al-4V Alloy: A Comparison between Abrasive Fluidized Bed and Laser Finishing

Abstract

Metal additive manufacturing is a major concern for advanced manufacturing industries thanks to its ability to manufacture complex-shaped parts in materials that are difficult to machine using conventional methods. Nowadays, it is increasingly being used in the industrial manufacturing of titanium-alloy components for aerospace and medical industries; however, the main weakness of structural parts is the fatigue life, which is affected by surface quality, meaning the micro-cracking of small surface defects induced by the manufacturing process. Laser finishing and Abrasive Fluidized Bed are proposed by the authors since they represent cost-effective and environment-friendly alternatives for automated surface finishing. A comparison between these two finishing technologies was established and discussed. Experimental tests investigated both mechanical properties and fatigue performances. The tests also focused on understanding the basic mechanisms involved in fatigue failures of machined Ti-6Al-4V components fabricated via Electron Beam Melting and the effects of operational parameters. X-ray tomography was used to evaluate the internal porosity to better explain the fatigue behaviour. The results demonstrated the capability of Laser finishing and Abrasive Fluidized Beds to improve failure performances. Life Cycle Analysis was additionally performed to verify the effectiveness of the proposed technologies in terms of environmental impact and resource consumption.

Energy consumption assessment in manufacturing Ti6Al4V electron beam melted parts post-processed by machining

“…Similarly, the range of Ra values along the perpendicular direction, indicated as , to the building one goes from 15.66 to 34.00 µm. These high values are well in agreement with the literature [ 37 ] but are also not adequate for high performances applications where EBMed titanium parts are usually used [ 38 ], so this evidence corroborates the needing for post-building surface treatments. As expected, roughness decreased after the turning process.…”

Electron beam surface remelting enhanced corrosion resistance of additively manufactured Ti-6Al-4V as a potential in-situ re-finishing technique

“…These drawbacks include lack of dimensional accuracy and inability to remove all porosities 73 . In addition, other drawbacks of mechanical polishing, similar to physical machining processes, are their need for repeatability for better quality, the use of mechanical tools and their contact with the surface, which could result in parts deformation and interrupt the dimensional accuracy 36 , 50 , 74 . Moreover, other surface finishing methods, such as chemical etching, are not environmentally friendly due to the involvement of chemical agents and solvents that are harmful to the environment as well as human safety 33 , 36 , 50 .…”

“…That is, the surface roughness of the manufactured part can be enhanced without the need for the part removal from the chamber. Indeed, the EBM manufacturing cost and time are important considerations that need to be dealt with in future studies to assess their industrial feasibility on a large scale 74 .…”

An Overview of the Latest Progress in Internal Surface Finishing of the Additively Manufactured Metallic Components

“…Atzeni et al [ 103 ] studied the influence of the abrasive fluidized bed method on the fatigue life and roughness of Ti-6Al-4V alloys manufactured by the electron beam melting method. As can be seen in Figure 14 , a smoother surface was obtained at the higher rotational speed of abrasive particles (6000 RPM), and surface roughness increased with the treatment times.…”

“… Average surface roughness of the AFB-treated samples for different speeds of particles and various treatment times [ 103 ]. …”