N22A-T003 TITLE: Novel Multiphysics Modeling of Electroplating Process for Metallic Aerospace Components

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML)

TECHNOLOGY AREA(S): Air Platforms;Materials / Processes

OBJECTIVE: Develop a coupled electro-chemo-mechanical model to optimize electroplating parameters, and to predict the influence of surface roughness, porosities/defects, and residual stresses due to zinc-nickel (Zn-Ni) coating on fatigue strength of high strength steel (HSS) aerospace components.

DESCRIPTION: Naval aircraft operate routinely in a very severe saltwater environment, and corrosion damage is the leading cause affecting fleet readiness and total life cycle cost. The Navy spends about $3.7 billion a year on corrosion maintenance and repairs. Corrosion fatigue can also lead to catastrophic failures of aircraft primary structures. Electrodeposition of cadmium coating on high strength steel (HSS) components has been very effective in providing protection against corrosion. However, cadmium—a known carcinogen—creates environmental hazards, and occupational safety and health (OSH) risks. Recently, a new alkaline Zn-Ni coating process has been developed and shown promises as a suitable replacement for cadmium plating.

HSS alloys such as 300M and 4340 are susceptible to hydrogen embrittlement. During the electroplating process, the released hydrogen gas could be absorbed into the substrate, which can cause the loss of ductility, static, and fatigue strength of the base metal. Furthermore, hydrogen can also be absorbed into the HSS components when the coating corrodes in service. This hydrogen re-embrittlement (H-RE) mechanism could also lead to premature structural failures.

In addition, surface roughness, coating thickness/uniformity, porosities/microcracking, residual stresses, and pre- and post-treatment can have a significant impact on not only the effectiveness and durability of the coating system, but also on the components’ fatigue performance. Electrolyte chemical composition, current density, part geometries, and anode-cathode placement/spacing and surface areas are also contributors to the plating variations.

Current process characterization, optimization, and qualification are predominantly empirical based requiring extensive testing, a costly and very time-consuming effort. This must be repeated for each of the HSS alloys.

The Navy requires an integrated suite of software tools that accelerate the optimization and qualification process, and quickly assess the impacts of electroplating on the structural integrity, including material properties and fatigue performance of HSS aircraft components (e.g., landing gears) subjected to naval operating environments. The modeling approach should consider the interplay between residual stresses, porosities/defects, and microstructure evolution on fatigue strength of the metallic materials. The proposed research should also provide a two-way coupling between the corrosion damage and mechanical stresses (internal/residual and externally applied) for capturing the synergistic effects of mechanical loading and corrosion on the integrity of the electroplated parts.

The specific aims are: (a) modeling residual stress generation during electrodeposition, (b) predicting fatigue strength of the base metal considering surface roughness, porosities/defects, and residual stresses, and (c) developing multiobjective optimization algorithm for the plating process.

PHASE I: Develop a modeling concept and computational framework for electrodeposition and optimization of Zn-Ni coating on a HSS (300M or 4340) structural component (e.g., landing gears). Demonstrate feasibility of the proposed concept to predict residual stresses, coating thicknesses, and fatigue performance of the electroplated part under constant and variable amplitude spectra. Develop a qualification testing plan for the optimized coating. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop multiobjective optimization algorithm for electroplating process. Develop and demonstrate a beta software tool for electroplating Zn-Ni coating on HSS (300M or 4340) parts. Validate the model predictions with experimental test coupons and representative structural parts subjected to constant and variable amplitude spectra. Perform qualification testing for the optimized coating in accordance with the test plan developed in Phase I. Demonstrate by testing that the corrosion protection and fatigue performance of the optimized Zn-Ni plated component under constant amplitude and variable amplitude spectrum to be equivalent or better than the cadmium plated part.

PHASE III DUAL USE APPLICATIONS: Demonstrate the scalability and effectiveness of the tools for different HSS alloys such as Aermet100, 17-4PH and HYTUF. Perform qualification testing on a full-scale component to validate the software predictions. Transition the tools to U.S. Government depots and commercial industries.

In addition to aerospace, the transportation industry—such as automotive—will benefit greatly from this technology for optimizing plating of transmission gears made from high strength steel alloys for better corrosion and wear resistance performance.

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KEYWORDS: electroplating; zinc-nickel coating; high strength steel; fatigue strength; corrosion protection; wear resistance

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