India’s Indigenous Engine-making Programme Kaveri to be Revived

[kbd-raaf]

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.

 

[MilSpec]

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.

(No need for sir, sandy will do fine)

To begin I am neither a metallurgy guy nor a have worked on engines manufacturing to give you any good insight, but from structural perspective it would be safe to say that the single lattice structure provides better distribution of longitudinal loading stress. Saying that keep in mind the fact that crystalline structure is never modeled in real structural design validation, what it essentially does from the design purpose is changes the youngs modulus for better flexural rigidity. Or atleast that is how I would interpret it.

I really dont have an answer for your about the casting question, The only thing that probably goes against the cold chamber casting would be controllable issue (Which I think can be solved by engineering PID loop of temp control) and for Hot chamber would be the melting point which might be higher for Fe-Ti alloys. Porosity is indeed lower on Inv castings and general finish is better. there are some really great VMC's that can machine the most complex profile out there, the cutter tech changed leaps and bounds, CNC cutting is not a very bad option especially if your production run is small....


i am not really sure what process is stumbling block for GTRE, but if I can recall my metallurgy class, you need to create your specific iron carbide diagram for your own alloy, i.e. create it in controlled environment. Once that is done then you can devise the additives and catalyst you would need to ensure controlled lattice structure in the alloy. Now when you go into the smelting furnace in the foundry there will remain variation, so you would need to setup a test run for at least 30 samples to get atleast 90% reliability confidence in your mix, All this is for one lattice structure, and this would increase with the number of alloy mixes you would want to test. Hence the process is indeed very lengthy.

and your queries were wonderful, it does feel good to remissness in the older college days, your queries did exactly that, hence thanks.

 

[kbd-raaf]

@sandy_3126

I'm doing a bit of research myself atm, I'll reply to your post soon.

Since @Dillinger used sir, I thought it was a good idea too. Not sure how courtesies work on a forum.

 

[Dillinger]

@sandy_3126

I'm doing a bit of research myself atm, I'll reply to your post soon.

Since @Dillinger used sir, I thought it was a good idea too. Not sure how courtesies work on a forum.

@sandy_3126 is armed, man, might as well be careful and call him sir.

As far as I am aware with Koraput we have all the requirements met from CNC to investment casting, nickle alloys and blisk. TBCs may remain an issue and are vital to increasing the temperature and performance in the hot zones (turbine)- the greater the temp the more the thrust. So TBCs like Yttria stabilized zirconia are required. The issue isn't just producing the materials, since we have even had samples of fabricated SCBs, the issue is to do so in the required manner and with the required QC/QR being met. It's a LONG story, will post on it in detail later.