Alloy 230

[Slacky]

Has anyone any experience with what phases/precipitates should generally be observed in wrought and solution treated alloy 230? We have found grain boundary films which are high in Lanthanum.

 

[unclesyd]

I would give Haynes a call about your concern. They have always been very helpful on different topics in the past.

We use 230 for grids for ammonia burner baskets and what little Metallography was mainly looking at the grain size and oxides. I don't recall anyone mentioning anything about the La content. We done a lot more physical testing in efforts to improve the life of material.

http://www.haynesintl.com/230HaynesAlloy.htm

 

[Metaljon]

Haynes 230 superalloy is a relatively new type of alloy with
excellent creep resistance strength, oxidization and corrosion resistance. The main constituents are Ni-Cr-W and the strengthening mechanism is solid solution strengthening. This alloy has between 0.005 and 0.05 wt% Lanthanum in the material which improves oxidation resistance. I would expect some Lanthanum migration to grain boundaries which is how the element produces improvement in oxidation resistance. What levels of Lanthanum are you detecting at the grain boundaries?

 

[Slacky]

Thanks Metaljon,
We experienced brittle fracture during processing and on analyzing the fracture face on the SEM found La rich areas particularly on grain boundaries with La anywhere from 2 to 16% using EDX. We have also seen a phase which appears to be ~30% La and ~62% Ni. I've read some literature that suggests that La combines with P, in C-Mn clean steels but at too high a level it will precipitate as a brittle La-Fe eutectic phase at grain boundaries affecting strength and toughness. Not sure if this is the same for alloy 230, but La-Ni forms rather than La-Fe??

 

[metengr]

I concur with unclesyd's recommendation. Haynes International has a reputable metallurgical support staff that know their product line.

 

[EdStainless]

sounds like the heat treatment has been messed up. This alloy has good ductility.

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Plymouth Tube

 

[Metaljon]

You would need to confirm the steel composition by OES to confirm Lanthanum levels to confirm within specification. I would not have thought that Lanthanum levels in the range of 0.005 and 0.05 wt% would cause any problem related to embrittlement. This alloy normally has good ductility. This alloy can suffer embrittlement when the lubricants are not removed from cold forming prior to annealing. It is essential to thoroughly clean the part of all traces of lubricant after forming as embrittlement of the alloy may occur at high temperatures during annealing if lubricant is left on.