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Multi-material WAAM: what interest for the industry? EDF use case

The Grade2XL project aims to develop multi-material WAAM for industry through the production of 8 demonstrators.

The WAAM process is an additive manufacturing technique well suited for the manufacture of metric-sized parts, such as those used in the energy sector. The use case proposed by EDF is a good example: the holding ring is a part of 1.2 m in diameter and about 290 kg.

It is a safety element which is part of a set constituting the cut-off valves of hydraulic dams. About thirty of these parts are replaced each year in France. Like several other parts, the dimensions of the holding ring vary for each hydroelectric plant, so it is difficult to manage stocks. In addition, the supply of this part can take between 10 and 12 weeks with the conventional supply chain, this is a long time compared to the cost of a plant shutdown, which can reach hundreds of thousands euros per day. One of the main interests of EDF about WAAM is the possibility to obtain such parts in a reduced timeframe: we believe it is possible to manufacture them in 4 weeks with this new technology.

EDF use case is the holding ring, it is a part of the cut-off valves of hydraulic dams.

EDF use case is the holding ring, it is a part of the cut-off valves of hydraulic dams.

Another advantage of the WAAM is that it allows the manufacture of multi-material parts. Initially, the holding ring is made of painted high-strength steel and the small area in contact with the mobile ring is coated with a copper-aluminium alloy to ensure good friction properties at the location of the dynamic seals . In the Grade2XL project, we are investigating the possibility of manufacturing this part with three different materials: a high-strength steel for the structural part, a stainless-steel coating for the areas in contact with water (anti-corrosion properties) and the copper-aluminium alloy coating on sealing contact areas.

Multi-material WAAM has many advantages, but it also presents several technical and scientific challenges, such as the compatibility between different materials or the choice of a heat treatment adapted to all the materials present on a single part. The Grade2XL project will have resolved some of these obstacles and demonstrated the viability and interest of the WAAM process for industry. EDF has already started to work on the qualification of the WAAM process for the manufacture of some spare parts, as the complementary part to the holding ring: the sealing ring, the results of Grade2XL will contribute to this process.

Author : Flore VILLARET, Research engineer in welding metallurgy and additive manufacturing, EDF R&D

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