State of the Art
Large propellers are currently cast from metal, while composite propellers are occasionally used in smaller dimensions. Additive Manufacturing technology is developed at lab scale and in industrial applications for highly complex parts (e.g. aero-engines) and where weight is extremely critical (airplanes). 3D-printing of large parts (> 1m) with complex twisted skins and closed cavities is limited to several lab scale experiments. Fatigue properties and productivity are too poor to satisfy maritime needs.
Objective
Develop a representative blade propeller demonstrator and identify fabrication risks to mitigate before introducing this solution on the market. Choosing Additive Manufacturing (AM) for production to provide great benefits for the entire production value chain.
Solution
The demonstrator propeller blade foresees development and proof of feasibility of a highly productive and reliable Wire Arc Additive Manufacturing (WAAM) process using different metal alloys, e.g. cupro-aluminium, martensitic or duplex steels. The process will feature a high deposit volume and a defect free and cost-efficient process. The demonstrator, coming as a propeller blade with 1.5-2 m diameter and less weight through internal cavities, will be tested against fatigue and corrosion, while hydrodynamic properties will be assessed by numerical simulation.
Within the scope of the project, a hollow blade demonstrator was designed, manufactured and tested. The size of the demonstrator (1,5m to 2m blade) is sufficient to allow an extrapolation of the use of the WAAM process to propellers of a larger size, allowing to address globally the propeller market. The first in the world of simplified demonstrative blade produced and showed the capability of the WAAM process to manufacture a hollow blade in 3-axis. An increasing number of the axis is necessary to manufacture the final representative of the hollow blade. Characterisation tests have been performed on specimens taken from test blocks. Results from metallographic examination, tensile tests, hardness tests, impact bending tests and corrosion test show that WAAM material has a better behaviour compared to equivalent casting material with the same chemical composition.
Potential
Additive Manufacturing processes for large structures will be enabled with significant efficiency improvements and cost reduction useable in other maritime applications and industries, such as general engineering, offshore etc. Design freedom arising from additive manufacturing bears immense potential across sectors. Proof of functional and economic feasibility for maritime real-scale applications will have a catalysing effect in the use of this technology. Propeller blades have wide application in maritime and energy sectors.