TECHNOLOGY AREA(S): Materials
OBJECTIVE: Establish a production technique for tungsten carbide (WC) cermets using a novel binder material that will improve ballistic performance and resolve environmental/industrial concerns associated with conventional cobalt-bearing WC cermets.
DESCRIPTION: Increasing soldier weapon lethality has been a long-standing goal of the US Army. The technology utilized in armor-piercing projectiles has not advanced significantly since the 1950’s. This technology gap currently aligns with the Secretary of the Army’s (SOA) Modernization Priority focused on Solider Lethality. An alternative binder material that imparts mechanical property improvement, and thus, penetration performance, could provide the revolutionary leap in soldier lethality that the Army seeks. ARL has developed an alternative binder system consisting of an oxide dispersion-strengthened, ternary alloy of iron, nickel, and zirconium that aims to provide improved properties/performance as a binder for WC cermets with reduced environmental concerns. The focus of this project is the research and development of a production process suitable for scale-up of innovative binder and consolidation technologies for tungsten carbide systems that can improve the material’s ballistic performance while also providing reduced environmental and industrial impact.
PHASE I: Develop and demonstrate feasibility for a method of producing tungsten carbide cermet materials with a cobalt-free, non-hazardous binder system through either conventional (e.g., hot pressing, sinter-HIP, etc.) or innovative (e.g., field-assisted sintering, additive manufacturing, etc.) methods. The binder composition, as well as the overall cermet system composition, shall be tailored to produce a material that meets or exceeds all of the following required benchmark properties: (1) Fully dense (>97% of theoretical density) (2) Homogeneous microstructure that is uniform across the specimen cross-section (3) Knoop hardness (ASTM C1326; 2 kg indentation load): 15 GPa (4) Fracture toughness (ISO 28079 and/or ASTM C1421): 11 MPa-m1/2 (5) Flexural strength (ASTM C1684): 3 GPa The latter three aforementioned properties account for an approximately 20% improvement upon conventional materials. Fracture toughness can be measured using the Palmqvist method for hard metals (ISO 28079) or the precracked beam (PB) method outlined in ASTM C1421. ARL is willing to provide the awardee with up to 100g of the baseline Fe-Ni-Zr binder powder to ensure that the focus remains on cermet consolidation with optimal microstructure and properties. However, the awardee can pursue the use of an alternative environmentally-friendly binder composition to the benchmark properties. To be considered environmentally-friendly, the binder must contain no more than 15% nickel, 0.1% cobalt, and 5% chromium by weight. The resultant deliverables of this phase would be feasibility demonstration of producing specimens that are within 15% of, meet, or exceed each of the five benchmark properties listed above with an accompanying final technical report containing complete details on the composition, processing methodology including processing parameters, test methodology and full data sets. ASTM - American Society for Testing and Materials ISO - International Standards Organization
PHASE II: Utilizing the production technique developed in Phase I, further developments will be focused on the fabrication efforts of near-net and net shape projectile cores of the WC-based composition. These projectile cores shall be in geometric agreement with a small-caliber core of ARL-acceptable geometry for ballistic testing. A drawing of said geometry shall be provided to the awardee by ARL at the start of Phase II. In Phase II, the offeror will be expected to produce and scale-up fabrication of the binder material through any method of their choosing. Further scale-up and optimization of the fabrication technique for producing the WC-based composition should be demonstrated. Optimization of the WC-based composition of the material may also be conducted to maximize properties/performance. Towards the latter part of year 2, an exploration into the potential dual-use applications for this material will be conducted with possible demonstration of prototype components and/or associated testing. Deliverables for this phase will be 100 projectile cores by the end of year one along with a year one summary report detailing all information on the composition, processing and testing methodologies and full data sets, and 1,000 projectile cores by the end of year two along with a final technical report, which will include a cost projection analysis for producing projectiles for the M993 or M995 system in addition to all information on composition, processing and testing methodologies and full data sets generated since the completion of the Phase II first year report. The end of year two deliverable should be produced in a single batch or by semi-continuous processing methods at net shape (i.e., requiring no rework or post-fabrication processing, e.g., flash removal) and meet the benchmark properties listed above. In addition, a report describing the assessment of the dual-use application(s), consisting of a technical review of the application, processing, preliminary results, and cost projection analysis, shall also be provided at the conclusion of year two.
PHASE III: Prototype projectile cores developed in Phase II would be integrated into full M993/M995 small-caliber munition system. This integration may require further design optimization for the particular munition. This technology would be transitioned to an ammunition manufacturer and/or an identified dual-use application manufacturer (e.g., cutting tools). Further development of dual-use opportunities for this technology will be executed with possible transfer to a commercial manufacturer.
1: J. Pittari III, J. Swab, K. Darling, B. Hornbuckle, H. Murdoch, S. Kilczewski, and J. Wright, "Investigation into sintering of ‘green’ tungsten carbide bodies with an iron-based binder," Int. J. Refract. Met. H., Submitted (2017).
2: J. Pittari III, S. Kilczewski, J. Swab, K. Darling, B. Hornbuckle, H. Murdoch, and R. Dowding, "High Strength and Toughness Cemented Carbide Containing Tungsten Carbide (WC) with Fine-Grained Iron (Fe) Alloy Binder," United States Patent and Trademark Office, Patent 15/807,604 (2017).
3: J. Pittari III, J. Swab, K. Darling, B. Hornbuckle, H. Murdoch, and S. Kilczewski, "Investigation into sintering of novel ‘green’ tungsten carbide bodies," Advances in Powder Metallurgy & Particulate Materials-2016, pp 532-538
4: Kotan, Hasan, et al. "Thermal stability and mechanical properties of nanocrystalline Fe–Ni–Zr alloys prepared by mechanical alloying." Journal of materials science 48.24 (2013): 8402-8411.
KEYWORDS: Tungsten Carbide, Oxide Dispersion-strengthened Alloys, Armor-piercing Rounds, Environmental Alternatives, Cutting Tools