Optimized High Performance Stainless Steel Powder for Selective Laser Melting Additive Manufacturing (AM)
Navy STTR 2016.A - Topic N16A-T007
NAVAIR - Monica Clements - navair.sbir@navy.mil
Opens: January 11, 2016 - Closes: February 17, 2016

N16A-T007 TITLE: Optimized High Performance Stainless Steel Powder for Selective Laser Melting Additive Manufacturing (AM)

TECHNOLOGY AREA(S): Air Platform, Materials/Processes

ACQUISITION PROGRAM: PMA-261 H-53 Helicopter Program Office

OBJECTIVE: Develop a stainless steel powder with advanced material characteristics to improve processability, part quality, and performance using an integrated computational materials engineering (ICME) framework to enable the use of selective laser melting (SLM) AM for the replacement, and future design of stainless steel components used in Naval aviation.

DESCRIPTION: Additive manufacturing (AM) has the potential to revolutionize part design and acquisition for the Navy. Further development is needed before AM is accepted for the production of structural components and current efforts to advance AM often overlook its foundation: the material. For many Navy applications, this material is typically a metallic powder used in a powder bed AM system. Current state-of-the-art metal powders, in particular stainless steel powders, have been found to be incapable of producing parts that meet the performance requirements for Naval applications without extensive post processing. Research has shown that powder characteristics like particle size, shape, and distribution; packing density; conductivity; and chemical composition have significant impact on a part’s microstructure which contributes to producing unsatisfactory parts. These properties have also been found to vary widely from supplier to supplier due to different powder processing techniques and self-established specifications. As such, many AM machine manufacturers impose limits on the powders they allow to be used in their machines forcing their consumers to purchase only the manufacturer’s specified powder or risk voiding their warranty.

A stainless steel powder with advanced material characteristics to improve processability, part quality, and performance for use in SLM AM for the replacement, and future design, of stainless steel components used in Naval aviation is sought. An ICME framework should be used to optimize the powder characteristics (e.g. compositional ranges, interstitial content, morphology, and conductivity.) 17-4PH alloy parts are carefully heat treated in order to obtain optimal properties by precipitating a 2nd phase strengthening. Similarly the powder alloy must be capable of achieving optimal properties via thermal processing. The powder must promote processability (e.g. size and shape consistency; high conductivity and packing density; wide melting range; reusability; and able to be used in a variety of powder bed AM machines) and produce as-built parts that exhibit quality (e.g. geometric accuracy and surface finish) and performance (e.g. strength, ductility, hardness, and fracture toughness) equivalent to or better than conventionally built 17-4PH parts.

PHASE I: Develop a stainless steel powder, which when used in SLM AM results in equivalent or better material properties as compared to traditionally manufactured 17-4PH. Design the selected powder using ICME tools. Establish feasibility of the developed powder by fabricating coupons and generating limited test data such as static and fatigue properties for comparison.

PHASE II: Optimize the metal powder characteristics through an iterative approach that includes modeling, fabrication, and testing of prototype parts. Initiate the development of the material properties database for the optimized design, through the fabrication and testing of a small, but complex shaped component. Demonstrate compatibility with a variety of laser melting machines.

PHASE III DUAL USE APPLICATIONS: Fully develop the design allowable database for the material. Demonstrate and validate the performance of the new material through component testing in a service environment. Transition the newly developed, optimized powder for use in the fabrication of Navy and commercial stainless steel aircraft parts through SLM AM. Stainless steel is used in a wide variety of industries (e.g. aerospace, automotive, energy, construction, and medical.) The desired AM-tailored stainless steel powder would provide these industries with an opportunity to incorporate SLM AM to produce high-performance, complex parts. This effort would also produce the groundwork needed to develop additional AM-tailored materials for other commercial applications.

REFERENCES:

1. Averyanova M., Bertrand Ph., Verquin B. (18 July 2011). Studying the influence of initial powder characteristics on the properties of final parts manufactured by the selective laser melting technology. Virtual and Physical Prototyping, 6:4, 215-223. Retrieved from http://www.tandfonline.com/doi/abs/10.1080/17452759.2011.594645#.Vaa5M8kpCyc

2. Gu H., Gong H,. Dilip J. J. S., Pal D., Hicks A., Doak H., Stucker B. (2014). Effects of Powder Variation on the Microstructure and Tensile Strength of Ti6Al4V Parts Fabricated by Selective Laser Melting. Solid Freeform Fabrication Symposium. Retrieved from http://sffsymposium.engr.utexas.edu/sites/default/files/2014-040-Gu.pdf

3. Vrancken B., Wauthle R., Kruth J.-P., Van Humbeeck J. (16 August 2013). Study of the Influence of Material Properties on Residual Stress in Selective Laser Melting. Proceedings for the Solid Freeform Fabrication Symposium, 1-15. Retrieved from http://sffsymposium.engr.utexas.edu/Manuscripts/2013/2013-31-Vrancken.pdf

KEYWORDS: Cost Reduction; Metal Additive Manufacturing; Part Quality; Stainless Steel; Powder Optimization; Material Characterization

TPOC-1: 301-342-8511

TPOC-2: 301-757-5524

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