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Application of Functionally Graded Materials to Extra-Large Structures

Periodic Reporting for period 1 - Grade2XL (Application of Functionally Graded Materials to Extra-Large Structures)

Reporting period: 2020-03-01 to 2021-08-31

Grade2XL will deliver a 3D-printing method for high-performance, multi-material large structures

Large engineering structures like turbines, bridges, or industrial machinery are still manufactured by traditional processes such as forging and casting. These processes do not allow engineers to control material properties locally in order to achieve anti-corrosion or hardness functions only at the exposed or loaded locations in the structure. Grade2XL project will tap into the potential of wire arc additive manufacturing. This method combines high printing rates with the ability to control material properties down to the nanoscale, enabling the design of strong and durable engineering structures. The project is expected to deliver devices of superior quality and performance, cut lead times by up to 96 %, and unlock massive cost savings for the maritime and energy industries. The following objectives were set to structure our ambitions:

Objective 1: Develop functionally graded materials and a high throughput WAAM process for multi-material deposition with in-line, contactless inspection features.

Objective 2: Demonstrate the added value of local control of material properties with WAAM to reduce the material use and lifecycle costs of large-scale manufacturing by at least 35%.

Objective 3: Roll-out WAAM as an economically viable and sustainable alternative to the conventional technologies – delivering the Industrial 4.0 revolution.
An initial selection of material combinations and shielding gases was made. Mono- and bi-material (graded) coupons were produced for five (out of eight) demonstrator cases. Material characterisation tests were conducted in WP 1 to evaluate the material properties in relation to the process conditions. The graded combinations were evaluated against the end-user requirements; where these were not met, alternative combinations were proposed and coupons were printed. All test results are documented in WP 5 , with the view of establishing dedicated fabrication procedures for WAAM. A novel, coupled thermo-mechanical Topology Optimisation algorithm was developed, and will be next extended for multimaterial optimisation.

The Super Active Wire Process (S-AWP) was extensively tested in WP 2, and used in the production of samples for WP 1. The deposition rate improvements were recorded, reaching or even exceeding 5kg/h for the stainless steels; this early result gives confidence in achieving the ambitious productivity targets set by the project. An in-line monitoring system was developed and is currently optimised for multimaterial printing. The system has been installed at both printing centres, to allow comparability of the experimental results at demonstrator level. Efforts are currently focused on correlating this system with the non-destructive inspection technologies developed in WP 3 In-line inspection. Two novel water-cooled torch designs that reduce the temperature build-up during deposition, supporting the increase in productivity. Printing strategies were defined for all demonstrators and documented in a dedicated deliverable(report), in WP 4 Demonstration. The product innovations (MaxQ in-line monitoring system) and two novel torch designs are soon to be commercialised.

The preliminary lifecycle assessment (LCA) and lifecycle costing (LCC) carried out in WP 6 showed that products manufactured with WAAM performed environmentally and economically better than conventional manufacturing. Reaching a large number of potential technology users entails direct, live demonstration sessions towards small and medium-sized enterprises. Although efforts have been made in WP 7 Dissemination and exploitation, the corona crisis has hindered this objective, as major trade fairs and events were cancelled in 2020, just after the launch of the project. Efforts are being made to build an active on-line presence. The roadshow is due to start in the second half of the project.

1. MATERIAL: controlling material properties at nano-level for properties on demand
We will create functionally graded (multi)materials, by controlling the two main factors governing the material properties: the chemical composition and the thermal cycle. Functionally graded materials will be developed, whereby desired properties will be created at specific locations a) by compositional grading, altering the chemical composition of the melt pool by adding different wires and b) by adjusting the deposition conditions. Topology optimisation methods will enable us to manufacture "properties on demand" in the graded structure.

2. PROCESS: high throughput WAAM for multimaterial deposition
High WAAM productivity will be achieved by a. transferring novel high throughput concepts to WAAM; b. developing multiple wire deposition systems. The productivity will increase from typically 2 kg/h to 5 kg/h, further doubling when a dual robot configuration is used. Heating strategies will be applied to mitigate distortion by redistribution of stresses. Cryogenic cooling will be used not only to control distortions and create certain microstructures, but also to increase production rates by reducing the inter-pass times. Non-destructive inspection devices will be integrated in the manufacturing line and coupled with an adaptive control system to allow real-time adjustment of process parameters and avoid defects.

3. SYSTEM: WAAM graded structures becoming “business as usual” for life cycle benefits
We will pair the unique possibilities offered by WAAM in terms of data recording with state-of-the-art detection methods to develop an in-line contactless inspection system for WAAM. Such a system will ensure first time right quality and facilitate qualification. A comparative lifecycle assessment will reveal the sustainability and cost benefits of WAAM grading. We will also develop qualification roadmaps for all WAAM produced components, to facilitate the adoption of WAAM as industry practice.

• WAAM-as-a-service;
• WAAM equipment, including WAAM (multimaterial) robotic deposition and cryogenic cooling equipment;
• WAAM wire materials;
• WAAM graded products (demonstrators) – followed by technology roll-out within the organisations of the involved end-users, to unlock massive financial and material savings.

The innovation work performed in Grade2XL will cut lead times by up to 96%, reduce material use by up to 65% and unlock savings estimated at 118 Million euro by 2030.
As our selection of challenging applications will demonstrate, the multimaterial WAAM will reduce cost by 35% to 85% and lead times by 67% to 96 %, and enable material savings of 30% to 65% overall. Functional grading will deliver a significant impact on the use of expensive materials, with savings of 81% to 94%. With the ability of WAAM to regenerate components back to the original shape through local, on-site repair, the maritime industry will be able to reshore jobs from China and further limit the environmental impact of the marine operations. We will also reach out to groups who can foster the creation of new value chains. Although fully automated, our approach on advancing WAAM will preserve current jobs and offer training for the future generation of WAAM engineers.
Ship propeller during WAAM deposition (source: RAMLAB)