Originally posted by pchupunkar
Another rookie question for the knowledgeable people regarding engine tech. Why is titanium not used for the blades? Isnt titanium used for all places which require high structural integrity, would that not make it a better choice for the blades.
Do the properties of titanium degrade in high temp & high pressure?
-Ni alloys have higher strength at higher temperatures than Ti alloys. AFAIK, there are no Ti alloys capable of operating in the temperature regime of Ni superalloys and satisfy all other requirements too. I believe Ti has severe oxidation problems too, but dont quote me on that.
-Intermetallics of Ti may be used to circumvent the above temperature problem, but then, with intermetallics you have other serious problems of ductility, toughness etc
-Ti alloys are a pain in the butt to form into complex shapes. Same with Ti aluminides and other intermetallics. One way is to go down the powder metallurgy route, but then, problems with process control and reproducibility in properties between different batches offsets any gains in other areas. Still, T-6Al-4V and similar alloys are used in the aerospace industry, but not in turbine blades.
-Ti is very expensive. 😀 (okay, but so is Ni superalloys..dont know exact prices though)
Edit: I think (again, not 100% sure, gotta check my books) that at the temperatures to which turbine blades are exposed, Ni superalloys actually have a higher specific strength compared to Ti alloys, simply because Ti becomes so weak at that temperature that its low density becomes useless as an engineering property.
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