i honestly don't understand in depth about turbine stuff (the only propulsion i have ever worked was my father 12 years old suzuki panther engine that would engulf the entire neighbourhood with strong diesel odour when warming up the engine) , but regarding the one statement that i bold on your quote , we need to expertise in metallurgy for such component right , or we can just import the processed metal needed for that component and manufactured it here ?
Yes indeed, for the utmost secrecy things between gas turbine's manufacturer in their product is the alloys that they are used.
The Aerodynamic, thermodynamic, as well as rotor dynamic of gas turbine are the things we can pursue and optimized even by our own endeavor ( not to mentioned with sophisticated state of the art software technologies available in the market for computational design and modelling ).
The main limitation in designing or developing more advance gas turbine are the material technology and the turbine cooling technology. We could have designed in the paper more efficient gas turbine, for example, by increase more compressor pressure ratio and burn it the higher temperature. But, what materials or alloy can withstand such higher temperature ? (concerning the current firing temperature is already high, let say 1200 -1400 Celcius), how to design the turbine blades and disc cooling path so that it can run in a long periods of time?( we are talking about 30,000 - 40,000 hours of operation), not just in hundreds of hours of operation than it will disintegrates .
The alloy at all section will be expand and shrink, back and forth, in a wide range of temperature ( from ambient temperature to over thousands of degree Celcius) as the engine will be in start/stop frequently. Designing such highly precision "fit and clearance" dimension all over the parts of gas turbine is already a big headache
What I can see from pictures above from Barata, we still have very limited expertise in the making of gas turbine, as it just capable in manufacturing "the skin" by far, whilst the "flesh and blood" and to "the bones" of the gas turbine it self still out of reach by us.
Like I was written on my previous postings, gas turbine is not a rocket science....it is more than a rocket science.