Comparative Quality Control of Titanium Alloy Ti–6Al–4V, 17–4 PH Stainless Steel, and Aluminum Alloy 4047 Either Manufactured or Repaired by Laser Engineered Net Shaping (LENS)

Abstract

Additive manufacturing attracts much interest for manufacturing and repair of structural parts for the aerospace industry. This paper presents comparative characterization of aircraft items made of Al 4047 alloy, Ti-6Al-4V alloy, and 17-4 precipitation hardened (PH) (AISI 630) stainless steel, either manufactured or repaired by laser engineered net shaping (LENS). Chemical analysis, density, and surface roughness measurements, X-ray micro-computed tomography (μ-CT) analysis, metallography, and micro-hardness testing were conducted. In all three materials, microstructures typical of rapid solidification were observed, along with high density, chemical composition, and hardness comparable to those of the counterpart wrought alloys (even in hard condition). High standard deviation in hardness values, anisotropic geometrical distortion, and overbuild at top edges were observed. The detected defects included partially melted and unmelted powder particles, porosity, and interlayer lack of fusion, in particular at the interface between the substrate plate and the build. There was a fairly good match between the density values measured by μ-CT and those measured by the Archimedes method; there was also good correlation between the type of defects detected by both techniques. Surface roughness, density of partially melted powder particles, and the content of bulk defects were significantly higher in Al 4047 than in 17-4 PH stainless steel and Ti-6Al-4V alloy. Optical gaging can be used reliably for surface roughness measurements. The implications of these findings are discussed.

Directed Energy Deposition of AISI 316L Stainless Steel Powder: Effect of Process Parameters

“…The total height indicates, in fact, that a slight over-building phenomenon is observed. Under-and over-building are pretty common issues in DED processes [28]. These issues are however, generally not considered to be critical for the building process.…”

Surface Roughness Considerations in Design for Additive Manufacturing - A Literature Review

“…When manufacturing metals using LPBF, the rapid cooling rates, powder spreading methods and directional solidification leads to material microstructural features, which can affect the part material properties such as porosity, non-equilibrium microstructures and anisotropic microstructures (Chen et al, 2019;Gorsse et al, 2017;Malz et al, 2019). Furthermore, defects can be caused by lack of fusion, unmelted or partially melted powder and gas entrapment occurring during the LPBF build process (Eliaz et al, 2020). These issues can impact the surface roughness of an LPBF part which in turn can influence properties (Aliprandi et al, 2019).…”

Measurement of the Anisotropic Dynamic Elastic Constants of Additive Manufactured and Wrought Ti6Al4V Alloys

“…However, thanks to its unique combination of properties, such as high strength, high fracture toughness, excellent corrosion resistance, superior biocompatibility, and low density, Ti6Al4V has also become common in the energy, chemical, marine, automobile, and biomedical industries [1,3]. Due to the significant advantages of additive manufacturing (AM) over traditional Ti6Al4V manufacturing processes, for example, the ability to form near-net-shape parts and complex geometries, a relatively short lead time, design flexibility, and minimal material waste, the interest in AM of Ti6Al4V has rapidly increased [1,[4][5][6][7][8]. Despite the abovementioned advantages of metal AM in general, and AM of Ti6Al4V specifically, the ability to fabricate fully dense, defect-free parts with homogeneous microstructure, good surface finish, and good mechanical properties are still considered to be a challenge [9][10][11].…”