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Additive Components Enhanced for Extreme Environments (ACE3)

Description:

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials

 

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

 

OBJECTIVE: The Additive Components Enhanced for Extreme Environments (ACE3) effort seeks to dramatically reduce lead times for critical components in turbine systems by enhancing the high temperature mechanical properties of additively manufactured superalloys through novel post-processing techniques. Proposals must focus on difficult to source, long lead time components that control system efficiency and lifetime; in particular, high-performance components used in the hot gas path of power and propulsion turbines. This topic is soliciting Direct to Phase II (DP2) proposals only.

 

DESCRIPTION: The Department of Defense (DoD) faces technical and procurement challenges with hot-section components in turbines (e.g., blades, vanes, seals, etc.) across various ground and aerospace platforms. These components operate in high temperature oxidizing environments while under extreme mechanical loads, requiring specialized materials and manufacturing techniques. Traditionally, these hot-section components are produced by casting nickel-based superalloys using a directional or single crystal solidification approach. These specialized casting techniques are costly and time-consuming, resulting in part replacement lead times averaging 18 to 36 months due to the highly specialized knowledge and equipment required to produce parts.  

 

The objective of ACE3 is to reduce critical hot-section turbine part lead times by exploiting the supply chain advantages of additive manufacturing (AM).. Melt-based AM of nickel-based superalloys offers advantages in precision, reduced scrappage, enhanced design freedom, shorter lead times, and a potential reduction in manufacturing costs compared to conventional directional or single crystal casting operations. However, AM techniques typically impart a fine grain size (e.g., 10-100 µm), resulting in inferior high-temperature creep properties compared to those of directionally solidified or single crystal materials [1]. Therefore, while additively manufactured blades and vanes are extremely attractive for next-generation engine designs and sustainment of DoD’s existing fleet, implementation is inhibited by poor high-temperature mechanical properties. To address this issue, the ACE3 project seeks to demonstrate new post-processing technologies that dramatically enhance the high-temperature mechanical behavior of hollow core or net-shaped nickel-based superalloys fabricated with laser powder bed fusion (LPBF) by transforming the as-built components from fine (<100 µm) grain structure to coarse (>1 mm) grain structure, resulting in creep performance improvement by at least an order-of-magnitude. Electron beam additive manufacturing is specifically not of interest due to inherent issues with short filament lifetimes and de-powdering of hollow core structures. 

 

Proposals must include: (1) an effective strategy for addressing difficult to source, long lead time components that control efficiency and lifetime in the hot gas path of turbine engines; (2) the proposer’s familiarity with turbine design including the basic functional and design requirements of hot-section components; and (3) alloy(s) of interest to be tested and a relevant component design to evaluate the proposed post-processing strategy. Proposals are not limited to current component designs – novel designs uniquely enabled through additive manufacturing are encouraged.

 

PHASE I: This topic is soliciting Direct to Phase II (DP2) proposals only. Previous efforts must have demonstrated a post-processing approach capable of achieving the milestones and metrics listed below supported by prior laboratory testing results: 

  • Demonstrated ability to perform post-processing on a commercially relevant nickel-based superalloy additively manufactured via laser powder bed fusion (LPBF), such as Inconel 738LC (IN738LC).
  • Demonstrated at least 10x increase in grain size relative to the as-built material along the build direction following post-processing.
  • Demonstrated the ability to retain at least 20% (area fraction) <100> cube texture in the build direction following post-processing.
  • Demonstrated the ability to control grain structure as a function of position within a test article with cm-scale precision

 

PHASE II: The ACE3 DP2 project seeks to build on the accomplishments listed in the Phase I section above to: (1) fully characterize the high-temperature mechanical properties of additively manufactured superalloy test specimens with and without the demonstrated post-processing strategy; (2) apply the validated post-processing strategy to an exemplary component design fabricated by LPBF; and (3) confirm the structure and properties match those expected from baseline coupon-level testing while also demonstrating the ability to successfully process components at scale with a scrap rate <5%. Final components must be subject to proof testing in a relevant environment to verify functional performance (TRL 6). Performers must bring their own exemplar design and propose a component-level test strategy sufficient for TRL 6 justification. The Phase II effort will consist of a 12-month base period with a 12-month option period.

 

Schedule/Milestones/Deliverables: Phase II fixed milestones for this program must include:

  • Month 1: Project kickoff meeting; all supporting positions identified in the proposal are assigned to personnel and names are provided to the Government.
  • Month 3: Preliminary high-temperature mechanical test results on additively manufactured superalloy coupons in as-built and post-processed conditions using the proposed strategy. Quarterly presentation detailing results.
  • Month 6: Complete mechanical test results demonstrating statistically significant improvement in high-temperature material properties. System requirements and preliminary design for processing exemplary components. Month 6 technical report and presentation detailing results.
  • Month 9: Final design, development plan and preliminary results for exemplary component processing. Quarterly presentation detailing results.
  • Month 12: Process demonstrated for the exemplary component, including measurements meeting the target geometry and microstructure. Process automation reduced to practice to produce sufficient parts for system-level testing. Month 12 technical report and presentation detailing results.

 

Option Milestones/Deliverables:

  • Month 15: Quarterly presentation detailing part manufacturing progress toward system-level testing.
  • Month 18: Components manufactured, post-processed, and delivered to test facility. Technical report and presentation detailing results.
  • Month 21: Results of system-level testing in a relevant environment (TRL 6). Post mortem analysis completed on tested components and assessment of outcome. Quarterly presentation detailing results.
  • Month 24: Final Phase II report and technical presentation summarizing all results, lessons learned, and potential transition path.  Technical reports must be delivered in Microsoft Word or PDF format; presentations must be delivered in Microsoft PowerPoint or PDF format.

 

PHASE III DUAL USE APPLICATIONS: The novel post-processing technology developed under this effort will have widespread application in both military and commercial gas turbine engines used in power generation and propulsion. Enabling additive manufacturing of hot-section components will achieve more reliable and efficient supply chains, a decrease in overall costs, and the ability to explore novel component designs for improved thermal efficiency and fuel economy.

 

REFERENCES:

  1. V. Kalyanasundaram, A. De Luca, R. Wróbel, J. Tang, S.R. Holdsworth, C. Leinenbach, E. Hosseini, “Tensile and creep-rupture response of additively manufactured nickel-based superalloy CM247LC”, Additive Manufacturing Letters 5 (2023) 100119. https://doi.org/10.1016/j.addlet.2022.100119.

 

KEYWORDS: gas turbines, power generation, jet engine propulsion, sustainment, advanced materials, additive manufacturing, high temperature mechanical properties

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