It's materials engineering when it comes to engines and manufacturing engineering. It is truly impressive, exclusive sciences that are not taught. Most of it is proprietary technology held only by a few suppliers in maybe 5 nations. The US and UK are the main top dogs when it comes to this (both the materials and manufacturing of GT and turbofans). Russia, Ukraine, and France are overall second tier compared to US/UK. China is a recent arrival and trying hard to reach that second tier category. It has more funding than Russia and Ukraine but not the vast decades of experience and building those industries like the other five nations. It has now got 10 years running record for WS-10 which is good and iterations of that base platform. The platform's core design is an American/French engine CFM which China produced components for? correct me if I'm wrong. But no one shows the materials and it cannot be reverse engineered unless you have the production methods. Even then you may not have the same production machinery and tools.
That was 1990s to early 2000s China. Now if it can put into service the WS-20 and CJ-1000 along with WS-15 and WS-19, it would be easily in that second tier category. No one taught China how to build the WS-10, how to fabricate its components, the tools and machinery used in the processes. It was all an iterative improvement on past lessons. The WS-10 wasn't China's first turbofan although it was the first domestically engineered and made one despite its core having a similar design based on a CFM HBR engine.
Japan may have an overall better technology base than China when it comes to this. They're particularly good at GTs but military turbofans haven't been given much attention. Ukraine was the centre of military propulsion industry in USSR outside of Russia. It accommodated tank engine design bureaus and manufacturers, helicopter engines, rocket engines, and of course fixed wing aircraft engines.
Materials science and manufacturing engineering is often quite a lot more iterative and demands time invested, experimentation, failures from experimentation/testing, and breakthroughs. No one shares a shred of information, rarely even to allies. Sold finished products don't count and reverse engineering a finished engine in terms of materials is like uncooking an egg. With China's mastering of single crystal blades, then hollow blades, super alloys used in engines, and various manufacturing technologies, it's really not missing anything from Ukraine in the materials and manufacturing side. The Motor Sich purchase could secure a particular small turbofan for China's trainer jet but Russia has an alternative product which can be bought. If not, China would just need to spend the time to develop one. It's not a matter of whether or not it could but a matter of how much time it would cost. Motor Sich's helicopter engines and HBR turbofans could also hold benefit for China since those fields seemingly have not been given as much resource as engines for fighters.
