I read up that aircraft compressor blades are generally made out of titanium. I was curious as to why is titanium the choice of material used for aircraft compressor blades? What alloys are involved and are there alternative materials used in the designing of such blades?
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1$\begingroup$ Likely duplicate: What material is used to make the hot sections of jet engines? $\endgroup$– minsCommented Apr 11, 2017 at 18:37
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2$\begingroup$ @mins the compressor is the cold section $\endgroup$– FedericoCommented Apr 12, 2017 at 11:10
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2$\begingroup$ @Federico: Yes, but in spite of the title, the answers cover all sections of the engine, including compressor. $\endgroup$– minsCommented Apr 12, 2017 at 19:18
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$\begingroup$ Titanium alloys are used as compressor blade materials in modern engines but I can't provide any official sources. $\endgroup$– Notts90Commented Apr 14, 2017 at 9:06
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$\begingroup$ Simple answer is, Titanium is light and strong and is good enough for the temperature range of the compressor. JT3D, RB211, JT9D, Olympus, Spey, CF6 all use Titanium disk or blades. According to "The Development of Gas Turbine Materials, G.W. Meetham" page 73 $\endgroup$– user3528438Commented Aug 10, 2017 at 21:22
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2 Answers
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Have found a reference to "high grade steel" and to titanium. According to the (paper format) book, the parameter that dimensions the compressor is the perimeter speed (tip speed) of the blades $u_2$.
For steel: maximum $u_2$ = 450 m/s. With a total inlet entry temperature of 300 K, pressure ratio is 4.2
For titanium which has a higher strength/mass ratio: $u_2$ can be up to 500 m/s, leading to a pressure ratio of 6.
The book was written at the time of the B757/767 engines so there may be more modern materials around.
Also refer to this answer.
Update
A more recent reference is provided by this presentation for the Trent 1000 engine:
- Fan and LP compressor blades are made from titanium alloy, containing small amounts of Fe, V, O, and Al.
- IP compressor: 8 stages of titanium blades.
- HP compressor: 6 stages of titanium blades.
The reason titanium is selected is that up to a certain temperature, titanium has the highest specific strength (strength/weight ratio), and in the compressor the temperatures stay below the transition temperature for nickel alloys:
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$\begingroup$ What is inlet entry temperature? 300K is just above room temperature. $\endgroup$ Commented Aug 10, 2017 at 21:10
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$\begingroup$ Inlet entry temperature is the ambient temperature plus $\Delta T$ from compression in the engine inlet cowl $\endgroup$– KoyovisCommented Aug 11, 2017 at 4:25
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Most famous one is Nimonic 263, which is 50% nickel and 20% Chrome and created with additions of Titanium and Aluminium. Used in Concord engines.
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$\begingroup$ Thank you. But according to the site you provided it applies to turbine blades due to its ability to withstand high temperatures. Would you happen to know which material would apply to the compressor section? $\endgroup$ Commented Apr 12, 2017 at 23:54