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China eventually decided against purchasing the RD-180 in favor of improving its YF-100 technology, realizing they would not learn anything this way. Amusingly Energomash's deal with the US for their Atlas V first stage engine included the blueprints for its design but not the metallurgical details and the manufacturing information. So for example you can reverse engineer an alloy composition but you need heat treatment details to produce the correct balance of ductility and strength. US engineers were expecting the turbine blades for ORSC to be some kind of superalloy (like SpaceX's SX500) to resist hot oxygen but instead Soviet engineers brilliantly pioneered a form of ceramic coating applied on top of fairly standard nickel alloy. Again the critical details of how this exotic coating was applied and any pre and post-treatment operations were missing.
There were estimates that it would have taken several billion dollars to completely recreate the engine. RD-180 engines cost $10M each for the 100 unit original order. In lower quantities the cost kept climbing to about $25M each. ULA was also of course completely reliant on Russian support for this engine...
China's current and future generation of engines likely also use the superalloys approach over complex thermal barrier coatings.
What China has always demanded is technology transfer, not finished products. China was willing to pay Russia licensing fees and promise not to compete with Russia in the market (as with the Su-27 technology introduction). But in such critical domains, Russia musttransfer the technology. Otherwise, it's meaningless.
This principle was established very early on. If you understand Chinese history—from the defeat of the Beiyang Fleet to being invaded by Japan in WWII—you'll know just how profound a lesson the inability to achieve defense independence has been for the Chinese people and the entire Chinese nation. That's why, since the Communist Party came to power, China has persistently pursued technological autonomy—even if the weapons were inferior, they had to be fully mastered domestically, free from foreign control.
So regarding the RD-180: since there was no technology transfer, China fundamentally never truly bought or deployed it. That's perfectly normal.
Russia has never given complete technology. Getting 70% is already considered decent—and even the provided technical documentation might not be usable. (Not maliciously so. Actually, before the widespread adoption of computer-aided manufacturing in the 1960s–1980s, paper-based document management was chaotic worldwide. The archived drawings of the Saturn V, for instance, differed significantly from the actual flying hardware.)
So key technologies still had to be developed domestically. Even if you received materials, you essentially had to start from scratch using them as reference. Back then, China's technical level was lagging, and it's not surprising that Russia was unwilling to sell (or priced prohibitively high—effectively a refusal).
In fact, the YF-100 also traces its roots to Russian technology (seems to be NK-33 / NK-23 or something else—far inferior to the RD-180/RD-170). The WS-15 is similar. China obtained prototype samples and partial documentation—physical prototypes of Russian/Soviet technology—and then redesigned everything step by step. The same goes for the WS-10 and WS-19 (one derived from an early version of the American CFM56—very similar to the F101—and the other from the F404).
But going from physical reference samples to completing the entire forward-development cycle for aerospace engines typically takes 20–30 years. Globally, China is the only country that has actually done this.
