# What turbine blade alloy did the Jendrassik Cs-1 use?

Wikipedia says that the first turboprop aircraft engine was the Jendrassik Cs-1 invented in Hungary by György Jendrassik.

It says it was supposed to run at 1000 hp but "combustion problems" limited it to 400 hp.

I would like to know what turbine blade alloy it used. Could not find this info online. I have a feeling the blade alloy limits were what limited the engine power, since that is the main limiting factors on gas turbines in general.

Note: The Hungarian version of the wikipedia article says the turbine ran at 550 C, and...

A turbinalapátokat 50% reakciófokú csavart, szárnyprofil keresztmetszetű hőálló acélból gyártották precíziós öntéssel, és speciális beerősítéssel szerelték a rotorba.

The turbine blades are made of 50% reactive twisted, heat-resistant steel with wing section cross-sections, and are specially mounted in the rotor.

Don't know what that means. 50% steel? Then what is the other 50%? Also, there is no citation for it.

• Turbine temperature mostly limits efficiency. Size and fuel consumption limits power. Jan 8, 2020 at 22:02
• Also, turbine has nothing to do with combustion, and the wiki page stated the room for improvements are the flame cans not turbine. Jan 8, 2020 at 22:06
• @user3528438 Yes I know that turbine temps and combustion problems are different things, but this is wikipedia and they confuse engineering things all the time. Most of it is uncited. The part you referenced, There was nothing inherently wrong with the design, however, and continued work on the flame cans should have allowed it to develop to full power. is uncited. Jan 9, 2020 at 6:34
• To the downvoter, what is wrong with the question? I don't see anything unclear or off-topic. Jan 9, 2020 at 6:34
• My money would be on Tinidur, a 30% Ni, 15% Cr alloy developed in 1936 at Krupp. Since it also contained 2% Ti, the name was a combination of Ti + Ni + dur from latin durum = hard. If György Jendrassik had asked the obvious sources of his time, that would had been the recommendation. British Nimonic 80 came 5 years later. Sorry, no source and no English Wikipedia page. Learned of the Jendrassik Cs-1 only today. Jan 19, 2020 at 0:13

Jendrassik's own patent from 1939 does not go in-depth into the alloys. However, for the turbine blade legs he mentions "austenitic [stainless] steel" as preferable (see PDF page 3).

From that era, a Swiss patent from 1937 on the materials of gas turbine parts also discusses austenitic steel, in particular (translated from German):

Alloy of an austenitic steel containing 25 to 35% of chromium, 25 to 35% of at least one of austenite-forming metal [e.g. nickel], 1 to 4% of titanium and 0.3 to 0.8 (preferably 0.4 to 0.6%) containing carbon, optionally up to 3% silicon and up to 10% molybdenum.

It is close to the composition of the 316 stainless steel (source), which has a mechanical maximum temperature of 590°C (source).

• I read through the patent but did not find any mention of the word "turboprop" or even "aircraft" or "airplane". Are you sure this patent is talking about the Jendrassik Cs-1? Wikipedia says its a 15-stage compressor and 7-stage turbine, but cannot really see that in the patent either. The years match up tho. Jan 24, 2020 at 18:55
• @DrZ214: One doesn't patent the number of stages, nor are model numbers included, sadly. As for the application (turboprop; flying), since the gas turbine didn't fly even once, that part of the invention can't be patented. I'm pretty sure it is the one, as far as pretty sure goes without consulting a patent historian (that was almost a century ago in a turbulent period).
– user14897
Jan 25, 2020 at 3:04

Looking up the Jendrassik CS1, Google belatedly brought me to this question; though my Hungarian is non-existent, I suspect the '50% reaction' refers to the turbine's design parameters; a 50% degree of reaction means the pressure drop across a turbine stage is shared equally between stator and rotor (i.e. between fixed and moving blades). As to materials, the turbine blading would probably have been an austenitic stainless steel of some kind; IIRC most of the early British gas turbines used 'Rex 78' stainless blading, which was an austenitic steel developed by Vickers-Firth.

Looking at the CS1's design, I very much doubt it could have been turned into a viable aircraft engine without extensive development and/or redesign. With 15 compressor stages the stage loadings would have been low, but then you'd run into all kinds of surge problems as on a single shaft many of the stages would be running away from their optimum conditions, especially as the engine didn't have a free power turbine. The combustion chamber doesn't look long enough for full flame development, and annular designs are notably tricky to get right.

• Welcome to AV.SE! Dec 30, 2020 at 1:20

What is the time frame ? Vitalium ( cobalt + chromium + Mo ) was one of the first turbine blade materials. Otherwise 50 % iron is not unusual ; for example the Incoloy group. But most of the high temperature materials have nickel as the major element . And contain Cr, Mo, Co , W , etc , and 1 to 20% iron. A temperature of 550 C / 1022 F is certainly not very hot in the turbine world so an alloy like Incoloy 800 H with 45 % iron plus 34 Ni, 21 Cr,1 Al, etc is reasonable. The relatively low temperature suggests an older design : So actually "steels" are a possibility. Stainless 310 ( 25 Cr , 20 Ni , balance iron ) and the high carbon cast version HK . And even stainless 309 ( 25 Cr, 12 Ni , balance iron ) , cast as HH. These alloys are used in great quantity as petrochemical furnace tubes at temperatures to 1700 F +. I believe I examined failed 310 blades or vanes from a mid-eastern stationary gas turbine in about 1970.

• Since it seems you couldn't be bothered to read the linked Wikipedia page: The Jendrassik Cs-1 was designed in 1937 and ran first in 1940. That is 20+ years before Incoloy. Jan 19, 2020 at 0:34
• I did not look at the history. But what I meant by "Incoloy" is not a product of Inco but a large group of Fe, Ni, Cr alloys with more iron than nickel ." Tinidur" is an example , I was familiar with essentially the same alloy under the name "A 286" which I have recommended for high temperature bolting. That is why I wrote "Incoloy GROUP" intending to cover a category with many different names which would address the "50 % steel" in the question. Jan 20, 2020 at 22:23
• A286 was a post-war US derivative of Tinidur. Also no candidate. Jan 21, 2020 at 11:23