Resolution and geometric limitations in laser powder bed fusion additively manufactured GRCop-84 structures for a lower hybrid current drive launcher

• Published in: Fusion engineering and design Vol. 173; no. C; p. 112847
• Main Authors: Seltzman, A.H., Wukitch, S.J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2021; Elsevier Science Ltd; Elsevier
• Subjects: Diameters; Horizontal orientation; Lasers; Launchers; Machining; Melting; Powder beds; Printing; Radio frequency; Rapid prototyping; Residual stress; Walls
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2021.112847

•Laser Powder Bed Fusion additive manufacturing enables rapid construction of lower hybrid launchers for fusion reactors.•Surface roughness depends on print angle, 45° overhangs do not require supports.•0.5 mm thick walls warp during the print process, 1 and 1.5 mm thick walls eliminates warping.•Sinusoidal motion of the build plate induced a 5 mm period 40 μm pk-pk surface waviness.•.Dimensional accuracy was within 40 μm, batch-to-batch variation was 10 μm. Laser Powder Bed Fusion (L-PBF), also known as Selective Laser MeltingTM (SLMTM), allows additive manufacture of lower hybrid current drive (LHCD) Radio Frequency (RF) launchers from a new material, Glenn Research Copper 84 (GRCop-84), a Cr2Nb (8 at. % Cr, 4 at. % Nb) precipitation hardened alloy, in configurations unachievable with conventional machining. The resolution and geometric limitations are tested to explore the limitations of L-PBF printing of GRCop-84. Printing holes in the vertical and horizontal direction are examined to determine the minimum cooling channel diameter. Internal stress limits the minimum thickness of vertical walls and septa to 1 mm, thinner walls warp during printing. Roughness is minimized on vertical surfaces and increases on both upper and lower surfaces as angle increases. Accuracy within 40 μm is typical on well supported structures.