Steel and nickel chromium alloys have been prominent and most used as turbine blade material although there are other materials such as tantalum carbides, tungsten and many more which I have no knowledge of. But these materials are not being used or even planned on being used in the near future why is that? Do the cons of these materials beat the pros of the ni-cr superalloys?
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2$\begingroup$ A close match as a question: aviation.stackexchange.com/q/14454/42636 $\endgroup$– Jpe61Mar 18, 2021 at 6:04
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$\begingroup$ Which material would be able to replace ni-cr alloy in future? $\endgroup$– Walter WhiteMar 18, 2021 at 7:03
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$\begingroup$ That would actually be a question for material sciencentists, not aviators 😉 $\endgroup$– Jpe61Mar 18, 2021 at 10:40
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3 Answers
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Turbine blades must withstand high tensile stresses at their blade roots and be resistant to cyclic stresses from fluctuating fluid dynamic loads- all of this at very high temperatures, and over great numbers of thermal cycles. This argues in favor of metallic blades and against ceramics in this application, because they perform better against fracture in tension and fatigue crack propagation.
answered Mar 18, 2021 at 5:41
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Tungsten for one has two major flaws when compared to other candidates listed.
The first one is actually told by the name of the material: tungsten -> tung sten = "heavy rock" in swedish. It is one of the heaviest elements having about the same density as gold. Even if it was a match in other properties for superalloys (which it is not), the weight of components made from it would be a serious problem. Heavy rotating masses are not desirable.
The second problem is the difficulty of the "workability" of tungsten. Very high melting point makes casting difficult, and it is also a very hard material to machine.
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I doubt anyone in the trade would call any first stage turbine material a "steel" although many contain some iron. Vitallium was one of the first alloys Cr and Co ( no iron). Carbides are not used as such although there is a myriad of intermetallic particles , some are carbides, that form in the alloys as they are heat-treated. I expect there will always be alloy development but many advances in blade and vanes are in ; surface coatings , axial cooling passages, orientated crystals / grains , single crystals , and things I never heard of. Apologies in advance to anyone knowledgeable in the field. Wikipedia has a fair introductory entry for gas turbine blade materials . One correction , they mention steam turbines which use dramatically different materials ; primarily 13 Cr martensitic stainless , I expect steam may also use low alloy steels but we only saw the failed 13 Cr blades.
