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Has there ever been any high carbon stainless steel made with iridium as one of the alloy components? Is there any research in this direction?

There is a paper from 2016 comparing various iridium structures to more well known/studied structures, with the finding that iridium dinitrogen exhibits the highest bulk modulus of any high pressure synthesized compound at 428GPa.

There is also a paper from 2011 studying various physical properties of iridium carbides with various stoichiometries, finding that iridium pentacarbide and iridium tetracarbide (with iridium germanide structures) are potential ultrahard materials.

Has any more work been done in this area, ideally looking towards applications for iridium as a component in high carbon stainless steel alloys?

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  • $\begingroup$ How may kilograms of iridium are refined each year? upload.wikimedia.org/wikipedia/commons/thumb/0/09/… $\endgroup$
    – Phil Sweet
    Apr 26, 2022 at 23:12
  • $\begingroup$ @PhilSweet 3-4 tons according to a quick google. According to your chart approximately 10^11x less than the amount of silicone refined each year (7000000 tons by another quick google), so a minuscule amount per year by that estimate. $\endgroup$
    – AJR
    Apr 26, 2022 at 23:16
  • $\begingroup$ @PhilSweet Actually we would have to take a ratio of the atomic masses of silicone and iridium to get to a tonnage comparison using your chart, but a factor of ~192/28 won’t make much of a difference in how tiny the estimate is by that method. $\endgroup$
    – AJR
    Apr 26, 2022 at 23:27
  • $\begingroup$ I think it is very unlikely. Platinum is used in very small amounts in a Titanium alloy for corrosion resistance . But otherwise I never heard of platinum group metals in engineering alloys. Apparently the alloys you are asking about are HK modified and HP modified; used as high temperature furnace tubes. The modified involves additions like W, Nb, ( and ?) added at just the right time for pouring centrifugal castings. Stress rupture properties are enhanced. Wisconsin Centrifugal may have info on the web. $\endgroup$
    – blacksmith37
    Apr 27, 2022 at 1:57

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The purpose of trace-element alloying agents in carbon steel is to form carbides at the grain boundaries that are more stable at high temperatures than iron carbide is and also to help stabilize whatever iron carbides are present. This increases the hot strength of the resulting alloy and also improves its strength at ambient temperatures by locking out ductility mechanisms like grain boundary sliding.

Existing alloying agents like chrome, vanadium, and tungsten do a fine job of this and are readily available at reasonable prices.

Now if we imagine that a platinum-group metal would do a better carbide-forming and stabilizing job than Cr, V or W, we then run into the issue that carbide forming and stabilization are not the only strengthening mechanisms at work in carbon steels- and to get even higher performance out of steel requires the addition of bulk quantities of nickel, chrome, cobalt, moly, etc. as substitutes for the iron to yield superalloys instead. This is also a well-known process that is cost-effective and common.

So... the real question is, even if iridium could be beneficially used as a bulk constituent in iron-based superalloys, would it hold any cost advantage over Cr, Ni, V or W?

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  • $\begingroup$ My majors were in pure math/physics, so my interest here is mainly in min/maxing reality as opposed to making the process feasible/preferable for actual applications — what is the ‘best’ steel superalloy we can make. It seems like osmium and iridium carbides should be prime candidates for maximizing bulk modulus/hardness/toughness, I was curious if there had been any (maybe aerospace or government weapons) research into these elements as alloying materials. $\endgroup$
    – AJR
    Apr 27, 2022 at 21:57
  • $\begingroup$ I have a masters degree in materials science/mechanical engineering and we were never taught anything about alloying precious metals with iron. $\endgroup$
    – niels nielsen
    Apr 28, 2022 at 0:02
  • $\begingroup$ If interested in superalloys , look at gas turbine blades. They have been calculating compositions to develop Laves phases, etc, for over 40 years. $\endgroup$
    – blacksmith37
    Apr 28, 2022 at 0:48

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