Effect of oxygen content in new and reused powder on microstructural and mechanical properties of Ti6Al4V parts produced by directed energy deposition

Titanium alloy powder used for laser-based powder bed fusion (L-PBF) process is costly. One of the solutions is the inclusion of a powder recycling strategy, allowing unused or exposed powder particles to be recuperated post manufacture, replenished and used for future builds. However, during a L-PBF process, powder particles are exposed to high levels of concentrated energy from the laser. Particularly those in close proximity to the melt pool, leading to the formation of spatter and agglomerated particles. These particles can settle onto the powder bed, which can then influence the particle size distribution and layer uniformity. This study analysed extra-low interstitial (ELI) Ti6Al4V (Grade 23) powder when subjected to nine recycle iterations, tracking powder property variation across the successive recycling stages. Characterisation included chemical composition focusing upon O, N, and H content, particle size distribution, morphology and tapped and bulk densities. On review of the compositional analysis, the oxygen content exceeded the 0.13% limit for the ELI grade after 8 recycles, resulting in the degradation from Grade 23 level.

Section: Flowabilitymentioning

confidence: 99%

“…A single-batch recycling strategy involves the depletion of a batch quantity of powder, to complete a series of manufacturing builds without replenishing. Post fabrication unused powder is sieved, to remove agglomerates, contaminants and oxidised particles [12]. The sieved powder is then reintroduced back into the L-PBF.…”

Section: Introductionmentioning

confidence: 99%

Reuse of Grade 23 Ti6Al4V Powder during the Laser-Based Powder Bed Fusion Process

Harkin

Nikam

et al. 2020

“…Rousseau et al studied the effect of the oxygen content in new and reused Ti 6 Al 4 V components for the DED process. After 10 runs they concluded that there was no oxygen pickup in the reused powder when compared to the original [133]. The main reason for this behavior of the powder was the argon protective atmosphere under which the tests were carried out, which protected the particles in their most reactive state.…”

Section: Reusementioning

confidence: 99%

Study of the Environmental Implications of Using Metal Powder in Additive Manufacturing and Its Handling

Arrizubieta

Ukar

Ostolaza

et al. 2020

Additive Manufacturing, AM, is considered to be environmentally friendly when compared to conventional manufacturing processes. Most researchers focus on resource consumption when performing the corresponding Life Cycle Analysis, LCA, of AM. To that end, the sustainability of AM is compared to processes like milling. Nevertheless, factors such as resource use, pollution, and the effects of AM on human health and society should be also taken into account before determining its environmental impact. In addition, in powder-based AM, handling the powder becomes an issue to be addressed, considering both the operator´s health and the subsequent management of the powder used. In view of these requirements, the fundamentals of the different powder-based AM processes were studied and special attention paid to the health risks derived from the high concentrations of certain chemical compounds existing in the typically employed materials. A review of previous work related to the environmental impact of AM is presented, highlighting the gaps found and the areas where deeper research is required. Finally, the implications of the reuse of metallic powder and the procedures to be followed for the disposal of waste are studied.2 of 25 sold in 2016 was 983, whereas, in the year 2017 this value rose to 1768 units, which implies an 80% increase [1].As far as economy and sustainability are concerned, AM offers several advantages over conventional manufacturing techniques, which confers many potential applications to AM in diverse industrial sectors, such as automotive, aerospace, biomedical, energy, and consumer goods [4]. In the aerospace industry, for example, AM enables aerospace motorists to create blades with much more complex internal cooling channels, allowing engines to run at higher temperatures and thus increase their performance [5]. In the report presented by the National Institute of Standards and Technology (NIST) of the U.S. Department of Commerce, it is stated that in aerospace engines titanium parts are machined down to size from large initial blocks, which leads to more than 90% waste material, material waste that could be reduced by using AM [6]. The European Commission in the Digital Transformation Monitor of 2017 presented similar numbers, where the disruptive nature of 3D printing was studied. It was estimated that by 2050, AM could save up to 90% of the raw material needed for manufacturing [3].Nonetheless, the possibilities of AM are not only limited to a reduction of raw material usage. The possibility of manufacturing lighter components could lead to energy savings, estimated between 5% and 25% by 2050, as well as a reduction in manufacturing costs of around 4-21% for the same period [7]. This trend is applicable to different industrial sectors. For example, SmarTech expects the overall market for AM in automotive to reach 5.3 billion USD in revenues by 2023 and to achieve 12.4 billion USD by 2028 [8].The lack of European and international standardization related to AM is proving to be an impediment to the...

“…The interstitial absorption of oxygen and other gaseous elements (such as nitrogen and hydrogen) leads to a change in powder composition. This is particularly evident when reusing Ti6Al4V powder [18][19][20]. Also, it has been shown that increased oxygen levels were present within spattered particles produced during the processing of stainless steel by the selective laser melting process [8].…”

Section: Introductionmentioning

confidence: 97%

Analysis of Spatter Removal by Sieving during a Powder-Bed Fusion Manufacturing Campaign in Grade 23 Titanium Alloy

Harkin

Nikam

et al. 2021

The Laser-based Powder Bed Fusion (L-PBF) process uses a laser beam to selectively melt powder particles deposited in a layer-wise fashion to manufacture components derived from Computer-Aided Design (CAD) information. During laser processing, material is ejected from the melt pool and is known as spatter. Spatter particles can have undesirable geometries for the L-PBF process, thereby compromising the quality of the powder for further reuse. An integral step in any powder replenishing and reuse procedure is the sieving process. The sieving process captures spatter particles within the exposed powder that have a diameter larger than a defined mesh size. This manuscript reports on Ti6Al4V (Grade 23) alloy powder that had been subjected to seven reuse iterations, focusing on the characterisation of powder particles that had been captured (i.e., removed) by the sieving processes. Characterisation included chemical composition focusing upon interstitial elements O, N and H (wt.%), particle morphology and particle size analysis. On review of the compositional analysis, the oxygen contents were 0.43 wt.% and 0.40 wt.% within the 63 µm and 50 µm sieve-captured powder, respectively. Additionally, it was found that a minimum of 79% and 63% of spatter particles were present within the captured powder removed by the 63 µm and 50 µm sieves, respectively.