[lewispollard]

How come Rhenium is in the list of metals without substitutes, but also given as an example of a metal that was successfully substituted by General Electric? Is it just that it serves a different purpose in smartphones that nothing else can be adequately used for?

[downer91]

Wikipedia's article seems to point to the idea that recently, super alloy applications are placing high demand on a supply chain that was not prepared for such a change in market trends.

I think rhenium diboride seems to be a useful substitute for tungsten carbide in places where tungsten carbide is useful for its hardness. Apparently rhenium is used heavily in the production of tungsten alloys, so there's an association, in that industrial pipelines involving tungsten tend to have a lot of rhenium on hand too.

Meanwhile the super alloys which involve high use of rhenium are nickel-rhenium alloys. Apparently GE has produced a series of super alloys named Rene alloys, and the compositions vary among each memeber of the series, some don't involve rhenium. Given that they seem to be proprietary products with military applications (mostly high temperature rocket engine nozzles) details are somewhat scarce.

Maybe the demand directly relates to how many rockets are being launched, and how many fighter jets are serviced for replacement parts or lost in crashes?