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I was wondering how blades and vanes are typically made in commercial jet engines. Would you typically use investment casting to make compressor blades or just in the turbine section to accommodate the cooling channels?

Also, how much does a first stage high pressure turbine blade cost? Are they more expensive on the newer engines, for example, the LEAP vs. CFM56?

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  • $\begingroup$ I found this video.It may provide partial answer. $\endgroup$ – Manu H May 17 at 7:55
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    $\begingroup$ Gas turbine blades are super-high-tech castings... americanscientist.org/article/each-blade-a-single-crystal $\endgroup$ – xxavier May 17 at 8:01
  • $\begingroup$ Thanks! Looks like the turbine blades are largely casted, and based on the video, the compressor blades seem to be forged - could you make a compressor blade with investment casting? Just trying to understand why some are forged and others are cast $\endgroup$ – Greg M May 17 at 14:53
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    $\begingroup$ @xxavier Please post that as an answer. $\endgroup$ – Bianfable May 20 at 7:37
  • $\begingroup$ @Bianfable The OP's question refers not only to the manufacture of turbine blades, but also to compressor blades and to turbine blade absolute and relative costs... The American Scientist article that I quoted covers casting methods for turbine blades only... $\endgroup$ – xxavier May 21 at 11:44
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As a summary,

The fan blade is made by shaping molten titanium in a hot press. When removed, each blade skin is welded to a mate, and the hollow cavity in the center is filled with a titanium honeycomb.

The compressor blades are made by casting

Turbine blades are made by forming wax copies of the blades and then immersing the copies in a ceramic slurry bath. After each copy is heated to harden the ceramic and melt the wax, molten metal is poured into the hollow left by the melted wax

Please refer to the following website, it is very interesting for the manufacturing process of the main engine parts:

http://www.madehow.com/Volume-1/Jet-Engine.html

Concerning the fan blades:

Each fan blade consists of two blade skins produced by shaping molten titanium in a hot press. When removed, each blade skin is welded to a mate, with a hollow cavity in the center. To increase the strength of the final product, this cavity is filled with a titanium honeycomb.

Concerning the compressor blades:

Casting is used to form the compressor blades. In this process, the alloy from which the blades will be formed is poured into a ceramic mold, heated in a furnace, and cooled. When the mold is broken off, the blades are machined to their final shape

Concerning the turbine blades, it is multi-process:

Turbine blades, however, are made by a somewhat different method than that used to form compressor blades, because they are subjected to even greater stress due to the intense heat of the combustor that lies just in front of them. First, copies of the blades are formed by pouring wax into metal molds. Once each wax shape has set, it is removed from the mold and immersed in a ceramic slurry bath, forming a ceramic coating about .25-inch (.63-centimeter) thick. Each cluster is then heated to harden the ceramic and melt the wax. Molten metal is now poured into the hollow left by the melted wax. The internal air cooling passages within each blade are also formed during this stage of production.

The metal grains in the blade are now aligned parallel to the blade by a process called directional solidifying. The grain direction is important because the turbine blades are subjected to so much stress; if the grains are aligned correctly, the blade is much less likely to fracture. The solidifying process takes place in computer-controlled ovens in which the blades are carefully heated according to precise specifications. The metal grains assume the correct configuration as they cool following their removal from the oven.

The next and final stages in preparing turbine blades are machine-shaping and either laser drilling or spark erosion. First, the blade is honed to the final, desired shape through a machining process. Next, parallel lines of tiny holes are formed in each blade as a supplement to the interior cooling passageways. The holes are formed by either a small laser beam or by spark erosion, in which carefully controlled sparks are permitted to eat holes in the blade.

The cost of old models parts could be very expensive because they are manufactured upon request, that was the case for Concorde engines.

The financial aspect of the question is beyond my scope

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  • $\begingroup$ At least some blades are 'grown' from a single seed crystal, within the confines of a mould, so that the finished product is itself a single crystal of metal. $\endgroup$ – Mike Brockington Jun 20 at 11:54

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