As the core component of a ship’s propulsion system, the marine propeller directly determines the vessel’s propulsive efficiency, navigation safety and service life by virtue of its material properties. The evolution of propeller materials, ranging from early wooden blades to modern high-performance metal alloys and composite materials, bears witness to the advancement of the global shipbuilding industry.

Historically, cast iron once served as the mainstream material for propellers of small low-speed vessels. Favoured by its low cost and easy casting, cast iron was widely adopted in the market. Nevertheless, cast iron suffers from low mechanical strength, high brittleness and short service life. Restricted by insufficient strength, thicker blade sections were required, which further impaired propulsive efficiency, and cast iron was gradually phased out.

Copper alloys later became the primary material for propellers. Manganese bronze, featuring outstanding mechanical strength, high elongation, favourable impact resistance and seawater corrosion resistance, coupled with low manufacturing difficulty, once emerged as the industry standard. However, manganese bronze has an evident drawback: poor resistance to cavitation erosion. After long-term operation, erosion pits tend to form on blade surfaces, undermining propulsive efficiency and even structural safety.

Aluminium bronze represents an upgrade over manganese bronze. Based on copper and aluminium with manganese, iron, nickel and other alloying elements added, it inherits the merits of manganese bronze while delivering lighter weight, higher fatigue strength and superior anti-erosion performance. Therefore, it has become the preferred material for propellers of large high-speed ships. Even so, aluminium bronze imposes stringent requirements on smelting and casting processes. Large castings are prone to slow-cooling brittleness, leading to high manufacturing costs and limiting its large-scale popularization.

Cast steel has also been trialled for propeller manufacturing. Although it boasts high mechanical strength and good impact resistance, dimensional deformation is difficult to control during casting, resulting in significant geometric deviations of propellers. It features high processing costs and weaker seawater corrosion resistance compared with cast iron, leading to a short service life. At present, cast steel is mostly used only for spare parts.

In recent years, non-metallic materials such as glass fibre reinforced plastic (FRP) and nylon have been applied to small inland waterway vessels. FRP propellers weigh merely 1/4 to 1/3 of copper propellers, featuring convenient handling, good impact toughness and seawater corrosion resistance. Yet their low mechanical strength and creep under long-term load render them incapable of meeting the demands of large vessels and deep-sea navigation.

With the development of global shipping, ships are growing larger and more specialized. Scenarios including polar navigation and deep-sea exploration impose higher requirements on propeller materials. Traditional materials reveal numerous deficiencies under extreme operating conditions. When conventional stainless steel propellers for large polar vessels are fabricated via casting, internal stress defects are hard to control and production cycles remain lengthy, failing to satisfy strict requirements for high-reliability, high-performance propulsion components for polar navigation. During operation, erosion pits may emerge on blade surfaces and even structural fractures may occur, posing severe threats to navigation safety.

Meanwhile, the global shipping industry faces rising energy conservation and emission reduction requirements. Propellers made of traditional materials incur high resistance and energy consumption, failing to match the needs of green development in modern shipping. Optimizing marine propeller materials has become an urgent task. Independent research and development of new high-performance propeller materials is an inevitable choice for China’s shipbuilding industry to break core technological bottlenecks and achieve high-quality development.

For a long time, core technologies for high-end marine propeller materials have been monopolized by a small number of overseas enterprises. China’s shipbuilding industry has relied on imports for key materials, which not only brings high procurement costs but also risks technical blockades and unstable supply chains. As China becomes the world’s largest shipbuilding nation with expanding ship exports, developing high-performance propeller materials with independent intellectual property rights is essential to secure industrial and supply chains. It also serves as core support for transforming China from a major shipbuilding country into a powerful shipbuilding nation.

Independent R&D of optimized propeller materials first generates cost advantages. For large and ultra-large vessels, imported high-end copper alloy propellers often cost tens of millions of RMB. New domestically developed materials achieve international advanced performance while cutting costs by 20%–30%, greatly lowering shipbuilders’ production expenses and boosting the international competitiveness of Chinese vessels.

Furthermore, independent R&D enables customized development tailored to the practical demands of China’s shipbuilding industry. Material systems with better adaptability can be developed for diverse scenarios such as polar transport, deep-sea scientific research and large container ships, addressing pain points that imported materials cannot satisfy for special applications.

The research team led by Professor Guo Chunyu from Harbin Engineering University is a typical representative of China’s independent innovation in propeller materials and manufacturing technologies. In response to the urgent demand for highly reliable, low-temperature-adaptable key components for polar transport equipment, drawing on long-term experience in underwater propulsion technology and leveraging the advantages of high-end equipment manufacturing in Suzhou, the team continuously promotes the engineering and industrialization of research achievements, striving to develop high-end marine equipment suitable for polar environments.

The team has tackled challenges in high-precision performance prediction for polar thrusters. Centered on potential flow theory and peridynamics, a propeller design and performance prediction software platform based on intelligent algorithms has been established, reaching an advanced domestic level and providing solid technical support for material optimization design.

The research team at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, has also embarked on independent innovation in propeller material optimization. Under the planning of Academician Xue Qunji, researchers at the Key Laboratory of Marine Key Materials began early-stage studies on bionic interfacial slip materials and drag reduction for marine vehicles. Targeting the industry-wide pain point of high energy consumption of propellers, the team innovatively introduced bionic material concepts into propeller surface modification. It has successfully developed a bionic skin drag reduction and energy-saving technology for ship application, realizing independent controllability of material optimization and application, and breaking foreign monopolies in drag reduction and energy-saving marine materials.

These cases fully demonstrate that persisting in independent R&D is the only viable path for China to optimize marine propeller materials. Only by mastering core technologies can China break away from reliance on foreign expertise, seize the initiative in global shipbuilding competition, and deliver robust equipment support for building a maritime power.

To address the drawbacks of traditional casting for large propellers of polar vessels, Gongzhi Marine Equipment Technology Co., Ltd., founded by the research team from Harbin Engineering University, innovatively introduced additive manufacturing into stainless steel propeller fabrication. By optimizing material preparation processes, the performance of stainless steel propellers has been greatly improved, exploring a new self-controllable route for manufacturing large propellers for polar ships.

Large conventional stainless steel propellers are produced by casting, which easily creates internal defects such as pores and shrinkage porosity accompanied by uneven internal stress distribution. Under extremely low temperatures and alternating loads, stress concentration may trigger fracture risks.

Additive manufacturing builds materials layer by layer. Compared with traditional casting, it produces fewer point defects with relative density reaching 99.5%, and defect sizes ranging merely from 0.6 to 200 micrometres, substantially enhancing material homogeneity. On this basis, the technical team introduced micro-forging processes including ultrasonic impact strengthening and hammer peening to further densify materials, eliminate inherent defects such as pores, remove residual tensile stress and introduce residual compressive stress. This effectively extends material fatigue life, avoids thermal deformation and hot cracking of components, drastically reduces the risk of fracture at blade roots, and markedly improves the reliability of propellers operating in harsh and complex polar environments.

At present, the team has developed a complete technical chain covering blade design, additive manufacturing, internal flaw detection and precision inspection for propellers, establishing an innovative manufacturing model for large, high-performance polar marine propellers. Compared with traditional processes, stainless steel propellers produced using the new materials and technologies feature superior material performance, shorten production cycles by over 30% and reduce manufacturing costs by roughly 25%, delivering prominent industrialization advantages.

Gongzhi Marine Equipment Technology Co., Ltd. continues to advance technological upgrading, aiming to integrate artificial intelligence into all key links of stainless steel propeller design and manufacturing. Relevant technologies include intelligent optimization design for polar propellers and intelligent path planning combining multi-wire multi-light systems with multi-manipulator linkage. The company targets building an internationally leading low-energy, highly intelligent propeller manufacturing system to further amplify the technical advantages of independent R&D. In the future, this technical system will be extended to manufacture larger-sized and more complex polar equipment components, offering stronger support for China’s polar transport fleets and polar scientific research undertakings.

Against the backdrop of energy conservation and emission reduction in global shipping, the bionic skin material for propellers developed by the Ningbo Institute of Materials Technology and Engineering, CAS marks a major breakthrough in surface material optimization for propellers, providing a brand-new independent technical solution for energy efficiency improvement of large vessels.

Over half of a ship’s energy consumption is used to generate thrust via propellers to overcome water resistance. Accordingly, lowering surface resistance and raising propulsive efficiency is critical to shipping energy conservation. Drawing inspiration from nature, dolphins can swim at high speeds underwater thanks to the unique microstructure, flexibility and mucus secretion characteristics of their skin, which effectively reduce hydrodynamic resistance during movement.

Inspired by this mechanism, researchers artificially synthesized bionic skin materials replicating features of dolphin skin. The innovative introduction of the “liquid-like” material concept solved the technical challenge of reproducing the long-term mucus secretion function of dolphin skin, enabling the application of bionic skin materials on propellers of ultra-large crude oil carriers.

In 2024, the first 300,000 DWT ultra-large crude oil tanker equipped with a bionic-skin propeller completed three crude transport voyages, operating for nearly 200 days and covering more than 35,000 nautical miles between coastal China and major ports in the Middle East, fully verifying the practical performance of bionic skin materials. Full-scale ship test data show that after covering propeller surfaces with bionic skin, vessel fuel consumption drops by approximately 2%. Based on the annual fuel consumption of a 300,000 DWT ultra-large crude oil carrier, over 300 tons of fuel can be saved every year, generating direct economic benefits of more than one million RMB while cutting carbon dioxide emissions by over 900 tons, delivering remarkable energy-saving and emission-reduction outcomes.

Industry estimates indicate that the material maintains an average energy-saving effect of around 1.5% throughout its 2.5-year service life, bringing considerable long-term economic and environmental benefits. Prior to full-scale application, this bionic flexible drag reduction material obtained product certification from China Classification Society (CCS) and complies with the International Convention on the Control of Harmful Anti-fouling Systems on Ships (AFS Convention), laying foundations for large-scale promotion.

The shipborne bionic skin drag reduction and energy-saving technology stems from joint research between the Ningbo Institute of Materials Technology and Engineering, CAS and COSCO Shipping Energy Transportation Co., Ltd. It represents a typical achievement of China’s independently developed technologies for propeller surface material optimization, offering a Chinese solution for energy conservation in global shipping and opening new research directions for subsequent propeller material optimization.

Beyond additively manufactured stainless steel and new bionic skin materials, Chinese research teams continue to optimize conventional high-end propeller materials, with independent upgrading of titanium alloys and high-grade copper alloys as priority directions.

Titanium alloys feature high strength, excellent corrosion resistance and outstanding fatigue properties, making them ideal high-performance propeller materials. They were adopted for propellers of special-purpose vessels as early as the last century. However, challenges including difficult smelting, high processing costs and poor weldability have long restricted large-scale application.

Through independent optimization of titanium alloy composition, Chinese researchers adjusted the proportion of alloying elements and added trace rare earth elements to refine grains. While preserving strength, casting and welding performance are significantly improved, smelting difficulties are alleviated, and material costs are reduced by roughly 15%, paving the way for wider adoption of titanium alloy propellers. Currently, domestically developed new titanium alloys have been applied to propellers of high-performance research vessels and high-speed ships, with service life more than doubled and propulsive efficiency lifted by approximately 5% compared with traditional copper alloys, achieving internationally advanced comprehensive performance.

To tackle slow-cooling brittleness in large castings of high-grade aluminium bronze, domestic iron and steel enterprises and research institutions have jointly carried out technical research. Independent composition optimization processes and post-casting heat treatment technologies have been developed to adjust cooling rates and improve grain boundary structures via trace element addition. This effectively addresses slow-cooling brittleness in large aluminium bronze castings, enabling China to independently produce aluminium bronze castings over 8 metres in diameter for large marine propellers and breaking foreign monopolies on high-end copper alloy materials for large propellers.

Currently, optimized domestically produced high-grade aluminium bronze materials have been deployed on large container ships of above 10,000 TEU and 300,000 DWT ultra-large crude oil carriers. Product qualification rates have risen from the original 60% to over 95%, accompanied by a cost reduction of more than 20%, thoroughly ending reliance on imports for materials of large high-end propellers.

China’s shipbuilding industry is undergoing a critical transformation period, and independent optimization research on marine propeller materials faces new opportunities and challenges. In the future, driven by artificial intelligence, new material technologies and advanced manufacturing technologies, marine propeller material optimization will develop toward high performance, environmental friendliness and intelligence.

In terms of technological trends, composite propellers will become an important research direction. Fibre-reinforced composite materials are lightweight, high-strength, corrosion-resistant and highly designable. They can substantially reduce propeller weight, boost propulsive efficiency and lower vibration and noise, making them suitable for special vessels and eco-friendly ships. Chinese research teams have achieved phased progress in carbon fibre reinforced composite propellers. With advances in resin matrix and fibre modification technologies, breakthroughs are expected for composite propeller application on large vessels.

Meanwhile, the application of smart materials on propellers merits anticipation. Smart materials capable of adaptively adjusting surface morphology according to navigation conditions can further optimize propeller hydrodynamic performance, maintaining optimal propulsive efficiency under varying speeds and sea states and cutting energy consumption further. In addition, developing eco-friendly materials constitutes a key direction. Environmentally friendly propeller materials free of nickel and cadmium that reduce heavy metal usage will be an inevitable trend to satisfy increasingly stringent international environmental regulations.

From an industrial perspective, stronger industry-university-research collaboration should be fostered. National-level R&D platforms for marine propeller materials need to be established to integrate resources from universities, research institutes and enterprises and accelerate the industrial translation of independent R&D achievements. China has already realized breakthroughs in propeller material R&D for polar marine equipment and ultra-large vessels. Going forward, application scenarios should be further expanded from high-end special ship types to conventional vessels, enabling newly developed materials to benefit the whole shipbuilding sector.

Overall, independent optimization research on marine propeller materials constitutes a core field for high-quality development of China’s shipbuilding industry. After years of research efforts, China has broken foreign technological monopolies and attained international leading positions in multiple sub-sectors. Sustained independent innovation and continuous upgrading of material technologies will provide firmer support for building China into a maritime and shipbuilding power, and contribute Chinese wisdom and Chinese solutions to the green development of global shipping.