Absorption of Nitrogen during Pulsed Wave L-PBF of 17-4 PH Steel

Abstract

In the fabrication of 17-4 PH by laser powder bed fusion (L-PBF) the well-documented occurrence of large amounts of retained austenite can be attributed to an elevated concentration of nitrogen present in the material. While the effects of continuous wave (CW) laser processing on in-situ nitrogen absorption characteristics have been evaluated, power modulated pulsed wave (PW) laser processing effects have not. In this study the effects of PW L-PBF processing of 17-4 PH on nitrogen absorption, phase composition, and mechanical performance are explored using commercially available PW L-PBF equipment and compared to samples produced by CW L-PBF. PW L-PBF samples fabricated in cover gas conditions with varying amounts of nitrogen demonstrated reduced absorption levels compared to those produced by CW L-PBF with no effects on phase composition and minimal effects on mechanical performance.

Selective laser melting of NiTi stents with open-cell and variable diameter

“…At 24 µs exposure time, the lack of adherence between the layers is similar to a lack-of-fusion porosity. The pulse duration can be too low for a stable emission of the laser source, which can emit a minimum of 20 µs long pulses at full power [55]. It is known that fiber lasers may have emission delays and ramped emission profiles, which may be longer with low power levels [49,56].…”

Interface Analysis between Inconel 625 and Cobalt-Chromium Alloy Fabricated by Powder Bed Fusion Using Pulsed Wave Laser

“…This will significantly enhance their durability and performance in corrosive environments [10][11][12]. Therefore, this technology represents a significant advancement in safeguarding the integrity of petrochemical processes and reducing the economic risks associated with corrosion-related failures [13][14][15]. LPBF enables the fabrication of multi-metal components by selectively depositing different metal powders in precise patterns [16,17].…”

“…Conversely, a PW laser with a duty cycle of 1.0 is essentially equivalent to a CW laser, thus resulting in a larger melt pool and slower cooling rates. The variation in heat input between PW and CW lasers leads to the differences in microstructure and material properties of metals [15,[28][29][30]. The precise control over laser energy and the ability to create short, intense pulses help minimize the HAZ in LPBF, thus reducing the risk of thermal distortion and stress.…”

Pharmaceutical Micropollutant Treatment with UV–LED/TiO2 Photocatalysis under Various Lighting and Matrix Conditions

“…In addition, recent work has shown the use of TiO 2 nanomaterials for the formation of C-C bonds through their photocatalytic properties [15], which has been shown to be useful for the synthesis of polysubstituted imidazolidines [16]. Other forms of photocatalysis have been used to remove endocrine disruptors in water [17] as well as in laser-powder bed fusion for the adsorption of nitrogen [18].…”