Photo: Screenshot from China Media Group

If the aero-engine is hailed as the “pearl on the crown of modern industry,” then the single-crystal turbine blade is the “diamond set upon that pearl.” At present, only five countries in the world — the US, the UK, Russia, France, and China — have independently mastered the complete technology chain for single-crystal turbine blades, covering the full spectrum from materials research and development, precision casting, to engineering application, China Media Group (CMG) reported on Tuesday.

The essence of an aero-turbine engine is that of an energy conversion device. It converts the chemical energy of aviation fuel into high-temperature and high-pressure thermal energy through combustion, then drives the turbine to rotate, transforming it into mechanical energy, and ultimately into the kinetic energy of the aircraft, said the report.

The higher the temperature that the engine’s hot-section components can withstand, the higher the energy conversion efficiency — resulting in greater thrust, lower fuel consumption, and superior overall performance. Therefore, single-crystal turbine blades operate under extremely harsh conditions. They are a critical factor determining the engine’s performance, reliability, and service life, and serve as an important benchmark for measuring a country’s aviation manufacturing capability, CMG reported.

Li Jiarong, chief engineer of the AECC Beijing Institute of Aeronautical Materials, along with his team, has developed a single-crystal superalloy with completely independent intellectual property rights that has reached the international advanced level.

Li was quoted as saying in the report that “we have achieved the independent development of single-crystal turbine blade materials in China. Our second-generation single-crystal superalloy, DD6, offers performance that is superior to or equivalent to the second-generation single-crystal superalloys widely used in Europe and the US.” 

Moreover, it has a lower production cost. DD6 has become the most widely used single-crystal superalloy in China and has saved the country a large amount of strategic resources, according to Li.

Over the years, the single-crystal turbine blades developed and delivered by the institute have been applied in multiple types of advanced aero-engines, providing strong material support for military and civil aircraft — represented by advanced fighter jets — as well as helicopters, said Li.
According to CMG, the core mission of single-crystal turbine blades is to operate safely, stably, and reliably for long periods in extremely harsh environments involving ultra-high temperatures, high pressure, high rotational speeds, and corrosive gas erosion. Single-crystal turbine blades operate at temperatures that already exceed those of ordinary steel and even approach the melting point of their own alloy — so why can they still maintain long-term, stable operation?

Yue Xiaodai, a researcher from the institute, said in the report that nickel-based single-crystal superalloys use metallic nickel as the base. Researchers scientifically design and precisely add a variety of alloying elements according to multiple performance requirements, including high-temperature strength, creep resistance, and high-temperature corrosion resistance. 

Although these elements have vastly different physical and chemical properties, the research team, through repeated experiments and persistent efforts, has not only achieved uniform melting and fusion of all elements, but also effectively controlled impurity elements, according to Yue.

Since the 1980s, the institute has taken the lead in developing single-crystal superalloys with independent intellectual property rights, along with China’s first single-crystal turbine blade and first single-crystal hollow turbine blade, among others. These achievements have filled multiple technological gaps in China, according to CMG.

The manufacturing of single-crystal turbine blades, from alloy smelting and preparation to final product delivery, involves more than ten major core processes. Each of these core processes is further subdivided into dozens or even tens of precise, detailed sub-steps. China has become one of only five countries in the world capable of independently mastering the complete technology chain, CMG noted.

Global Times