During Soviet and subsequent Russian era, the jet engine technology development regarding turbine section, has been concentrated on directionally solidified turbine blade production. They have in house perfected the directionally solidified crystals to their own needs by attaining equiaxed crystals (these are crystals that have mostly axes of equal lengths.) .
By perfecting air cooling channel geometry and ceramic coatings they have managed to keep the boundary grain defects to a minimum and achieved acceptable high performance from these blades.
Directionally solidified blades are in essence layers of crystals. But due to their layered construction, under extreme heat and centrifugal forces the layers move unevenly away from each other, giving boundary grain imperfections and causing the Crystal lattices to deteriorate. Hence shorter lifecycles on engines especially if they are pushed hard too often.
Russians, according to western sources, have dabbled in Single Crystal blade manufacturing in some of their AL31 series engines. But did not get too far. AL41/AL51 series engines, according to unofficial sources may contain single crystals. But the fact remains that the Russian engines predominantly are produced with directionally solidified turbine blades.
It is also a known fact that the Russian jet engines’ combustion chambers are designed as shorter than western ones. Although this may give certain advantages, it also increases the chance of throwing out unspent fuel hence a smoke when pushed hard. (This however is less prominent in later engines). When you have a school of thought and design set on a specific way to produce your engine, it is not always feasible and workable to add new tech that works in the West. Hence may be their struggle with single crystals?
@Nilgiri may shed more light on this issue.
The significant difference in the "pyramid sizes" so to speak stem from the quality control (QC) related to the larger feedback loop of mass production/application available in the ecosystem (and then proximate ecosystems)
There exist roughly summarized two versions for countries engaged in the endeavour, from what I have seen from experience:
Loop 1:
(capital machinery and HR pool <----> QC <---> RnD)
IP is achieved concurrently in each (bidirectional flow) and is not HR compartmentalised.
QA (qual. assurance) is often just QC+ and not dedicated separately.
Specifics depends on the military and govt agency of the country, its organisational skills, funding and first dibs on HR stock from institutes of the country and so on.
Tighter units run, relevant starting investments and operating expenditures needed.
So ultimately more relevant for the military projects (low relative production scale) where commercial scale is not yet so big and developed yet (where production scales are high).
Loop 2:
(IP "1.0" --->capital machinery/logistics/HR--->production run QC---->service results/opex/reliability/QA----> QC studies---->RnD--->IP 2.0)
Larger production scale oriented (i.e commercial), military production scale "nests" within and/or is parallelized/orbited/induced (as its own loop 1) to it given the larger body gravity so to speak.
QA is discretized away from QC with its own HR. QC "studies" becomes a field in of itself. There are variants to loop 2 regarding this (and branch offs to consultancy/cooperation with others etc), it all depends on the company.
Bidirectionality is limited, there is cohesive standardised directional loop and processes involved regarding this.
Single crystal (SX) vis a vis directional solidification is just one notable visible representative apex of it (i.e how loop 2 can produce it commensurately to having just loop 1 in play).... there are others (think peaks in a mountain range).
In any case the more like loop 2 (comprehensive with commercial scale etc past the military scale) one has, folks that know something about statistics/stochastics will quickly grasp the importance of this scale and ability to have the much larger feedback operation (for win win of both).
Its essentially an applied real life monte carlo simulation done at large scale and higher "real life" variability with "hard" real results to measure as well (say 10 thousand unit inputs that are simulated)....compared to a more limited one (say just 10 or 100)....or a fully virtual simulation.
A military driven/niche command economy process and or a starting friction/onshoring ecosystem thus starts with loop 1 (its the seed and sapling etc).
"Loop 0" can be thought of as just RnD/DNA by itself (with no application/production "fuel/energy" provisioned/realised or unknown to the outside observer). i.e some jigsaw piece in the puzzle. It isnt really a loop, it has to be integrated with something to be realised as an early loop 1.
Example of loop 0 in russia w.r.t SX:
Loop 2 is the larger plant and tree in more full fledged way, reliable proven shade and sprouting fruit and new seed in cycles.
USSR achieved something like a 1.5 here (loop 1 achieved, loop 2 partially achieved by economy of scale) for its relative time at its relative apex.
Russia had retreated mostly to loop 1 (relatively speaking now) given funding and economic realities/constraints (both within itself and competitiveness of rest of world)
It shows:
https://www.airguide.info/s7-group-...-in-russia-advocates-for-reverse-engineering/
Speaking at the Russian Industrialist Forum, Elin highlighted that the PD-14 engines have only 3,600 flight hours between overhauls, significantly shorter than the 40,000 hours typical of Western engines like the CFM International CFM56.
So these establish the reliability economics of the older "directional solidification" vis a vis SX (even in just loop 1)...as to the final acceptable returns/costs in your macro-ecosystem.
Very similar to why any powerplant in any kind of vehicle (military or mass produced civillian) may not necessarily use everything you have technically unlocked IP wise....there are trade-offs production and "blood flow" expenses to all limbs involved in that...impose on this if you do not have the raw commercial scale backing it for example.
i.e Essentially what you describe with the Russian AL series not having the commercial equivalents in play (both raw production capacity wise and time/MRO feedback wise) that say the US has with GE and PW.
China is now starting to push from loop 1 to loop 2....but where it is exactly in the 1.5 zone between the two can only be seen with more time and hindsight later....especially as there is competition from other/allied economic sectors and china's own larger economic problems/dillemas playing their role too that remain to be seen regarding impacts here.
This is part of why the Chinese "actual military budget" estimates are often gauged as lot higher but at same time not really production side stuff "yet" likely due to frontloaded "starting" RnD soaking up lot of resources and impacting immediate return on investment (ROI).
i.e its not same 1:1 structure for the spending of say US and western ones regd their capex/opex as they have fleshed out their IP database/experience tree far more still and this reflects in the higher (matured) transfer rate to direct production in the official budgeting.
i.e what is the starting friction and intial rolling friction when RnD stuff is frontloaded intensely....compared to mid and late stream rolling friction which is lot lower (and premium RnD can both be funded and allocated to work on higher tier incremental advantages).
Hence why difference in ROI seen in immediate way between spaceX and NASA similarly I mentioned earlier in the US space thread:
We will have to see, NASA has a huge RnD budget and massive capital (both physical and human) that is frontloaded on it (so it brings the costs up).
But this pays dividends strategically for the US to create spaceX et al commercial ecosystem downroad as well to begin with.
Govt agency vs private company , what are the contexts, feedback loops and so on or next chunk of years is still ongoing thing.
Concerning jet engine corporate (publicly owned + listed) like say my knowledge of what Ive seen in PW/UTC (now raytheon, who's market cap is ~ 140 billion USD) and w.r.t departments that are RnD oriented compared to those that are production/application/sales oriented,
these ROI differences can again be seen within same company. i.e I have seen say the HR expense tabulations (compared to profitability) for segments of the company organisation. Some are sources and some are sinks (of revenue, net revenue, profitability and so on) but both are important in end for the final sum of things as shown in the earlier loops.
The final ROI and value addition etc end up being an agglomeration....just like if you took the "space sector" as a larger combined US entity somehow.
Anyway these are the economy of scales and time/experience integrals involved to establish and entrench in loop 2.
In Turkiye's case it would be related to high degree to how TEI is able to grow/operationalise in next 10 years or so.
There is an emerging "loop 3" that I might get to in a later reply, but it would need good establishment of loop 2 first.
