I am not sure which issue were specific to blisk process, blisks to my knowledge can be manufactured by CNC machining and or investment casting, now single crystal or monocrystalline lattice has nothing to do really with the blisk but with the controlled cooling of the material most likely in investment casting with the use of catalyst and additives for Fe-ti alloys. because of allotropy of steel, it's the funkiest material, based on the iron carbide diagram for the material, it can exist in multiple lattice structures which ca be manipulated for pecific applications, I am not sure how they achieve it in gtre. Now when I think of it, i can reckon why that might be an issue. For manufacturing of the blisk, i dont think that would be a huge issue, but yes the mono crystalline lattice for the the alloy might have posed problems especially if the alloy wasn't from home made recipe.
For your second question, I cant answer it, I have never worked with engines hence i dont know much about it....
A couple of questions sir,
Why would anybody want to machine a blisk blade when there are casting options available?
If I'm not wrong, investment casting options are more expensive per cast than die casting whilst generally having poorer properties. Why do they not use die casting? Is it the porosity issue?
There is also the option of direct injection die casting which provides for better properties through a slower, more controllale cooling rate as well as a lower cost per unit.
Also what is the benefit of a monocrystallic structure for turbine blades? I understand they have lower thermal creep, is that it? Epitaxy is a proven method for single crystal growth, why is GTRE having so much trouble taking advantage of such processes?
I apologise for my naivete and seemingly pointless questions, I'm just very curious.