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Joining of Dissimilar Materials for Hypersonic Applications


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Hypersonics 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 section 3.5 of 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: A methodology or methodologies to join ultra-high temperature ceramics to a variety of dissimilar substrate materials such as carbon-carbon, ceramic matrix composites and lightweight metals. DESCRIPTION: The U.S. Army must develop highly maneuverable hypersonic weapons that can survive high-G shock loads and harsh aerothermodynamic environments in a GPS-denied environment. To enable these requirements new materials and new manufacturing methods must be developed. There has been increasing desire to develop vehicles and projectiles that travel at the speed of sound and beyond. Materials with melting temperatures of 2000C and higher, ceramics based on silicon carbide (SiC) and silicon nitride (Si3N4) as well as carbon-carbon (C-C) composites, were developed and investigated to handle the aerothermal heating experienced at nose tips and leading edges of vehicles traveling at these velocities. The desire to push velocities into the hypersonic regime requires the development of materials with oxidation resistance and thermomechanical properties that can handle aerothermal heating to 3000C. The temperature requirement alone severely limits the available materials. Carbides and/or borides of hafnium (Hf), zirconium (Zr), titanium (Ti) and tantalum (Ta) fall into this category as do composites based on these materials and potentially high-entropy ceramics (HEC) that are multicomponent ceramics. While these materials meet the necessary temperature requirement and significant effort has been made in improving the properties at these temperatures the geometric complexity of the components as well as the cost associated with the manufacturing these materials it is currently impractical to expect these materials to be employed as monoliths in this application. What is more likely is the development of components comprised of multiple materials. Ceramic matrix composites (CMCs), C-C, and lightweight metals could be used as the structural component and can be produced cost-effectively and with the necessary geometric complexity while a UHTC layer on top of the component will protect the structural material from the extreme environments experienced during hypersonic flight. This will only work if these dissimilar materials are properly joined together to take fully take advantage of the benefits of these vastly different materials. The need to join dissimilar materials is not new. Methods such as welding, brazing and solid-state joining have been explored to create innovative ceramic/metal systems that result in improved impact resistance or that can function in advanced diesel and turbine engines as well as a variety of other applications. Success has been limited as a major challenge has been overcoming the residual stresses that develop at the interface due to the significant difference in thermal expansion of the materials. These residual stresses, if not property controlled, lead to generated of cracks and damage that lead to property degradation and reduced reliability of the joint. The focus of this effort will be the development of cost-effective methodologies to join these dissimilar materials to produce multi-material components that can survive the extreme environments encountered during launch and hypersonic flight. The focus will be on joining an ultra-high temperature ceramic to a carbon-carbon composite. A potential advantage over previous joining attempts is that the thermal expansion coefficient of these materials can be tailored to minimize or control the level of residual stress in the system increasing the likelihood of the success. PHASE I: The offerer will demonstrate a method or methods of joining a UHTC (preferably a ZrB2-SiC composition) to a C-C composite and a Zr metal substrate. Treating the UHTC and/or substrate surface and/or the use of a filler material(s) between the UHTC and substrate to promote joining are permitted. At a minimum the following will be performed: • Microstructural characterization of the joint area to determine the extent and quality of the interface including the edges of the interface as well as identifying any damage to the UHTC or substrate that may have occurred due to the joining process, • Measurement of residual stresses that develop at the interface as well as in the UHTC and the substrate material, • Mechanical characterization of the UHTC/substrate joints at room temperature to determine the interfacial tensile and shear strength, • Perform fracture analysis of the mechanically tested specimens to assess joint quality and identify the failure process, • Determine the oxidation resistance of joined UHTC/substrate materials at temperatures up to 1200C, and • Perform thermal shock testing by heating the joined material to 1200C followed by a rapid quench to room temperature in water. A successful joining method will be one where the room temperature interfacial shear and tensile strength are ≥ 150MPa and ≥ 70MPa, respectively. Any joined material that meets these strength metrics must also survive thermal shock testing, material remains joined with minimal to no damage of either material or the joint, in order to be considered a success. PHASE II: Utilizing the successful fabrication techniques developed in Phase I the Phase II effort will have two primary tasks. One will be focused on the optimizing the joining procedure to achieve higher interfacial properties as well as increased oxidation and thermal shock resistance plus expansion of the material selection for the UHTC (inclusion of Hf-based compositions and/or high entropy alloys) and if appropriate the substrate material. The other objective will be the development and testing of procedures and methodologies to fabricate near-net shape and net shape components with complex geometries, such as leading edges and curved surfaces, needed for hypersonic flight. The characterization tasks from Phase 1 will be repeated on any joined materials fabricated with an optimized joining techniques or any newly developed material combinations with the following changes: • Characterization of the UHTC/substrate joints to determine interfacial mechanical properties such as shear and tensile strength from room temperature to 2000C, • Oxidation resistance of the joined UHTC/substrate material will be determined from room temperature to 2000C, and • Thermal shock resistance of the joined UHTC/substrate material will be determined by heating the joined material to 2000C followed by a rapid quench to room temperature. Additional testing and evaluation will include: • Conduct burner rig tests at temperatures up to 2000C in an oxidizing environment to determine the performance and lifetime of the joined material, • Determine the performance of the joined material at high G shock loads (up to 25000G), and • Determine the performance of near-net and net shape components with appropriate complex geometries by exposing them to the harsh aerodynamic environments experienced during hypersonic flight. Success will be determined if the joined material system with a complex geometry has an interfacial shear and tensile strength of ≥ 150MPa and ≥ 70MPa, respectively at 2000C, survive thermal shock testing with the material system remaining intact with minimal to no damage of either material or the joint. PHASE III DUAL USE APPLICATIONS: It is envisioned that the R&D conducted as part of this STTR will provide the foundation of a commercially available method for joining the dissimilar materials needed for military weapons systems to survive and provide maximum performance in the extreme environments experienced in hypersonic flight. Of specific interest will be the development of material systems that can handle the environments experienced by a nose cone and other leading edge applications. REFERENCES: 1. F.A. Mir, N.Z. Khan and S. Parvez, “Recent Advances and Development in Joining of Ceramics to Metals,” Mat. Today: Proceedings, 46 [15] 6570-6575 (2021) 2. M.B. Uday, M.N. Ahmad-Fauzi, A.M. Noor and S. Rajoo, “Current Issues and Problems in Joining of Ceramic to Metal,” in Joining Technologies, M. Ishak, ed., (2016) 3. E. Wuchina, E. Opila, M. Opeka, W. Fahrenholtz and I. Talmy, “UHTCs: Ultra-High Temperature Ceramic Materials for Extremen Environmental Applications,” Elec. Chem. Soc. Interface, 30-36 (2007) 4. W.G. Fahrenholtz and G.E. Hilmas, “Ultra-High Temperature Ceramics: Materials for Extreme Environments, Scripta Mat., 129, 94-99 (2017) 5. R. Loehman, E. Coral, H.P. Dumm, P. Kotula and R. Tandon, “Ultra High Temperature Ceramcis for Hypersonic Vehicle Applications,” Sandia National Laboratories, SAND 2006-2925 (2006) 6. F. Monteverde and L. Scatteia, “Resistance to Thermal Shock and to Oxidation of Metal Diborides-SiC Ceramics for Aerospace Applications, J. Am. Ceram. Soc., 90 [4] 1130-1138 (2007) 7. W.G. Fahrenholtz, G.E. Hilmas, I.G. Talmy and J.A. Zaykoski, “Refractory Diborides of Zirconium and Hafnium,” J. Am. Ceram. Soc., 90 [5] 1347-1364 (2007) 8. S.A. Alvi, H. Zhang and F. Akhtar, “High-Entropy Ceramics,” IntechOpen 9. J. Gild, Y. Zhang, T, Harrington, S. Jiang, T. Hu, M.C.Quinn, W.M. Mellor, N. Zhou, K, Vecchio and J. Lou, “High-Entropy Metal Diborides: A New Class of High-Entropy Materials and a New Type of Ultrahigh Temperature Ceramics,” Sci. Rep. 6, 37946 (2016) KEYWORDS: Hypersonic Flight; Ultra High Temperature Ceramics; Joining; Bonding; Thermomechanical Properties
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