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A number of years ago, I remember hearing of a technique to manufacture the leading edge surface of a hypersonic jet (or something aerospace related) where multiple sheets of metal were welded together in a specific pattern to produce a laminate. Before welding, a layer of some sort of was placed between the metal so that when heated it would evolve a gas, inflating the unwelded pockets between the two sheets to create a super-thin cooling channels between the two layers.

What is this called? Was it a concept or is it used in industry?

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Aside from "evolving a gas by heating" (which sounds improbable IMO) the sounds like superplastic forming and diffusion bonding, which are standard manufacturing techniques.

In SPF the metal layers are bonded together in a pattern with "holes" in the bond, and inert gas is used to "inflate" the component into its final shape within a mold.

Diffusion bonding has been a "solution looking for a problem" for about 40 years, until the aerospace industry had the need to make metallurgically "perfect" bonds between large surfaces with complex shapes. The principle is very simple: make two surfaces with a high degree of accuracy, hold them together under moderate pressure, heat them up so that the atoms can diffuse across the boundary. The main disadvantage is that it is a relatively slow process - the diffusion takes minutes, compared with seconds for welding etc.

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  • $\begingroup$ I think you got it in one! Not sure why I thought the mask was used to produce the inflating gas, but it has been more than a few years since I heard of it. $\endgroup$
    – Mitch
    Aug 10 '20 at 1:10
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Titanium hydride.

Re: hydrogen embrittlement.

"Titanium metal powder is produced industrially by heating ground titanium hydride to 600◦C and applying a vacuum. When this reaches 10−3Pa the hydrogen is completely removed." - Ullman's Encyclopaedia of of Industrial Chemistry (2011)

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  • $\begingroup$ The last thing you would want in a high-tech component would be hydrogen embrittlement of the metal! $\endgroup$
    – alephzero
    Aug 9 '20 at 19:15
  • $\begingroup$ Titanium hydride is a known blowing agent for metal foams. Hydrogen embrittlement may be mitigated with baking, also a known process. $\endgroup$ Aug 9 '20 at 20:35

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