UNCLASSIFIED
UNCLASSIFIED
U.S. ARMY COMBAT CAPABILITIES DEVELOPMENT COMMAND – ARMY RESEARCH LABORATORY
Effects of atomization gas on 17-4 PH StainlessSteel build properties
Frank Kellogg1, Andelle Kudzal2, Josh Taggart-Scarff1, Ryan Rogers3, Brandon McWilliams21Survice Engineering, Belcamp MD2CCDC Army Research Laboratory, APG MD3Bowhead Science and Technology, Belcamp MD
RAMP-MD 2019 Metals Additive Manufacturing Symposium, Bel Air Md,May 2019
Distribution A, cleared for public release
UNCLASSIFIED
UNCLASSIFIED
2
• Army needs:• Manufacturing at the point of need• Hard to find legacy parts• Decrease long lead times• Design on Demand• Small quantities without need to restart major production
• ARL capabilities:• Open architecture manufacturing equipment• DMLS: ProX 100, ProX300, ProX320, EOS M100• E-beam : Arcam A2X• DED : RPM 222• Lab scale gas atomizer• Powder characterization:
• Morphology and size: Horiba LDA, Camsizer 2• Powder rheology: Brookfield PFT610
INTRODUCTION
UNCLASSIFIED
UNCLASSIFIED
33
17-4 PH STAINLESS STEEL
• Martensitic, precipitation hardened stainless steel • Combination of common use, high mechanical strength and readily
available powder make AM 17-4 a good candidate material for in-field part replacement
Element Content (%)Iron, Fe 73
Chromium, Cr 15.0 - 17.5Nickel, Ni 3.0 - 5.0
Copper, Cu 3.0 - 5.0Manganese, Mn 1.0
Silicon, Si 1.0Tantalum, Ta 0.45Niobium, Nb 0.45
Nb + Ta 0.15 - 0.45Carbon, C 0.070
Phosphorous, P 0.040Sulfur, S 0.030
UNCLASSIFIED
UNCLASSIFIED
44
LASER PROCESSING PARAMETERS
Image from 3dsystems.com
PROX DMP 100
• AM Processing Parameters
• Laser Power : 49 W
• Laser Scan Speed : 140 mm/s
• Hatch Spacing : 0.07 mm
• Powder Layer Thickness : 0.03 mm
• Powder: 2 batches
• Commercially available
• 1 batch atomized in N2
• 1 batch atomized in Ar
This project: a summarization of experiments examining how atomization gas changes build properties.
UNCLASSIFIED
UNCLASSIFIED
55
BACKGROUND
Figures from “Welding Metallurgy and Weldability of Stainless Steels” by John Lippold and Damian Kotecki (originally from ASM Metals Handbook (8th Ed, Vol 8, p 291) via Hansen, 1958, Constitution of Binary Alloys, 2nd Ed and via Baerlacken et al. 1958, “Investigations concerning the transformation behavior, notched impact toughness, and susceptibility to intercrystalline corrosion of iron-chromium alloys with chromium contents to 30%”, Stahl un Eisen, 81 (12)
• Fe-Cr phase diagram• Gamma loop
• Austenite stability window enlarges due to N2• Atomization in nitrogen stabilizes austenite, creates retained
austenite in as-manufactured parts
UNCLASSIFIED
UNCLASSIFIED
66
CHARACTERIZATION
• XRD starting powders
UNCLASSIFIED
UNCLASSIFIED
77
CHARACTERIZATION
• XRD after AM
UNCLASSIFIED
UNCLASSIFIED
88
MICROSCOPY: ARGON ATOMIZED, AS-BUILT
400 µm 100 µm
50 µm 10 µm
XY
AM Melt pool boundaries
UNCLASSIFIED
UNCLASSIFIED
99
MICROSCOPY: N2 ATOMIZED, AS-BUILT
400 µm 100 µm
50 µm 10 µm
XY
AM Melt pool boundaries
Austenite rich
UNCLASSIFIED
UNCLASSIFIED
10
• N2 atomized powder used in as-built parts leads to higher strength and hardness but lower ductility and elongation
MECHANICAL PROPERTIES
N2 Gas Atomized
Ar Gas Atomized
N2 Gas Atomized
Ar Gas Atomized
UNCLASSIFIED
UNCLASSIFIED
1111
• 6 mm diameter• 120 mm length wrought samples• 90 mm length AM samples • HAZ Lengths
• Wrought: 39.73 mm• N2 AM: 26.8 mm• Ar AM: 25.47 mm
HAZ SIMULATION
Build ( Z )Direction:
• Gleeble simulation of welding to see:• If AM 17-4 has the same degree of weldability as
wrought 17-4 • Effects of atomization gas
UNCLASSIFIED
UNCLASSIFIED
1212
MICROSCOPY: WROUGHT, POST HAZ
50 µm 10 µm
50 µm 10 µm
Hot End
Cold End
UNCLASSIFIED
UNCLASSIFIED
1313
MICROSCOPY: ARGON POWDER BUILD, POST HAZ
50 µm 10 µm
50 µm 10 µm
Hot End
Cold End
XZ
UNCLASSIFIED
UNCLASSIFIED
1414
MICROSCOPY: N2 POWDER BUILD, POST HAZ
50 µm 10 µm
50 µm 10 µm
Hot End
Cold End
XZ
UNCLASSIFIED
UNCLASSIFIED
1515
DELTA FERRITE
Figure 2.3b from “Welding Metallurgy and Weldability of Stainless Steels” by John Lippold and Damian Kotecki (originally from Castro and Tricot, 1962, “Études des transformations isothermes dans les aciers inoxydables semi-ferritiques á 17% de chrome, Memoires Scientifiques de la Revue de Metallurgie, Part 1: 59:571-586, Part 2, 59: 587-596.)
• Formation of δ ferrite• Fe-Cr-C pseudobinary diagram at 17% Cr
• C1 is a (Cr, Fe)23C6 carbide
• δ ferrite can prevent solidification cracking during welding• Also can lead to embrittlement, lower mechanical properties, and worse
corrosion prevention• Often heat treated out after welding
UNCLASSIFIED
UNCLASSIFIED
16
• Atomization gas influences mechanical properties, microstructures, and weld behavior• Neither good nor bad:
• Proper heat treatments• Design around properties• Design for implementation (welding?)
• N2 atomized powder leads to parts with:• Higher UTS• Higher hardness• Less δ ferrite after welding
• Ar atomized powder leads to parts with:• Higher ductility• Single phase microstructure
• Need to know entire history of the powder before building
CONCLUSIONS
UNCLASSIFIED
UNCLASSIFIED
17
ACKNOWLEDGEMENTS
The research reported in this document was performed in connection with contract/instrument W911QX-16-D-0014 with the U.S. Army Research Laboratory. The views and conclusions contained in this document are those of SURVICE Engineering and the U.S. Army Research Laboratory. Citation of manufacturer's or trade names does not constitute an official endorsement or approval of the use thereof. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation hereon.
The research reported in this document was performed in connection with contract/instrument W911QX-17-C-0021 with the U.S. Army Research Laboratory. The views and conclusions contained in this document are those of Bowhead Science and Technology and the U.S. Army Research Laboratory. Citation of manufacturer's or trade names does not constitute an official endorsement or approval of the use thereof. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation hereon.