The main objective of this project was to develop and validate a cost-effective and environmentally benign nanocrystalline electroplating/electroforming process that is capable of producing material, both for structural and functional components, that fully conforms to the mechanical and electrical property requirements for current and future copper-beryllium (CuBe) alloy needs and applications.
The primary technical approach used in the project was to investigate nanotechnology processing methods to optimize the material properties via microstructural design and control. This method utilized grain refinement to the nano-scale (instead of age-hardening with CuBe or work-hardening with current CuBe alternatives) to produce suitable alternative materials to CuBe for insertion into applications within the defense sector. The technology is based on nanostructured materials (e.g., high strength, high wear resistance, high fatigue performance, excellent corrosion resistance, low coefficient of friction, excellent coating adhesion, and low roughness) made by pulse electrodeposition, which allows for the retention of numerous benefits associated with plating (e.g., low cost, near-net-shape processing, low buy-to-fly ratio, and non-line-of-sight application).
The project consisted of two phases: Phase I - “Proof-of-concept demonstration” and Phase II - “Process optimization and performance testing.” It focused on demonstrating the technology in three distinct product forms: (1) bulk material for rod/bushing applications, (2) Nanometal/composite hybrids for components typically formed from sheet metal, and (3) Nanometal enabled conductor wire.
In Phase I, the use of pulse plating with environmentally benign plating solutions was found to produce nanostructured materials having a number of significant benefits as a CuBe alternative, including high strength, good hardness, high wear resistance, low friction, and good ductility. These materials could be produced with low surface roughness, low stress, no porosity, and moderate-to-high build rates; attributes important for the near-net generation of bulk forms. These materials could also be plated in thin electroformed shapes and applied to composite substrates with high adhesion for the fabrication of Nanometal/composite hybrid parts and stand-alone textured films, or they could be plated continuously on copper wire for the fabrication of Nanometal-enabled conductors.
Phase II continued the work from Phase I to a demonstration and validation scale, effectively demonstrating that pulse plating with environmentally benign metal/alloy plating solutions can produce nanostructured materials. These nanostructured materials have a number of significant benefits over CuBe, and conform to property requirements for current and future CuBe alloy needs within DoD. The most promising nanostructured material systems for CuBe-replacement applications identified in Phase I were further optimized and tested in Phase II, including nanostructured copper (nano Cu), nanostructured copper nickel (nano CuNi), nanostructured nickel-cobalt (nano NiCo) alloy, and nanostructured cobalt (nano Co) alloy. The team demonstrated and validated the manufacturing process and performance of the nanostructured materials in three distinct product forms: (1) bushing applications, (2) Nanometal/composite hybrids for components typically formed from sheet metal, and (3) Nanometal enabled conductor wire.
The main technical highlights for each of these three areas are summarized below:
Bushing Applications – The nano Co alloy bushings have significantly higher hardness, tensile and compressive strength, and showed no wear, no galling, no permanent deformation, less noise, and better friction in the sub-scale bushing test when compared against CuBe.
Sheet/Foil Applications – Nanostructured metal in sheet/foil showed excellent fatigue strength, electrical conductivity, and could be combined with carbon fiber composite to generate a high-quality hybrid with higher strength and stiffness at a significantly reduced weight.
High Strength Wire Applications – The nanometal/copper hybrid wire manufacturing process was successfully scaled to produce over 20,000 feet of wire for further demonstration/validation testing. The high-strength conductor wire had similar mechanical properties as CuBe wire with improved conductivity. A minor surface defect found on the wire, however, prevented the ability to strand the wire and perform full-scale validation testing.
This project developed an environmentally benign nanostructured alloy with significant performance enhancements in mechanical properties (in components such as bushings) relative to CuBe alloys. By retaining copper as the principal base metal, the approach minimizes the degree of deviation from current practice (and experience), thereby potentially accelerating the adoption of the technology by the defense sector.