ESR vs VAR refining 1

[RedVette]

When strictly comparing the integrity of nickel and cobalt-based superalloys refined by either electroslag remelting or vacuum arc remelting (excluding triple-melting and powder processing), which is generally the better choice? My brief research showed reports arguing the benefits of both over the other.

Do all nickel and cobalt superalloys undergo one of these two refining process or are specifications that allow for plain air induction melting without any subsequent refining process?

Thank you very much.

 

[tbuelna]

High strength nickel and cobalt alloys are usually quite expensive, so they are only offered in vacuum melt quality. There can be a huge difference in fatigue/reliability characteristics between an air melt quality and a vacuum melt quality of a particular alloy. Both ESR and VAR processes can produce a high quality product.

However, there are some nickel alloys (like Inconel 625/AMS 5599) that are widely available in air melt quality. These nickel alloys are used more for their corrosion and high temperature capabilities than their ultimate strength.

 

[MagBen]

Var is normally more expensive than ESR.
VAR: when clearliness is critical. But some alloys can not use VAR, such as N-bearing alloy, vacuum would suck it out.
ESR: the structure is critical. Since the solidification process is quick and kind of directional, the microstructure is finer.

 

[EdStainless]

Remelt becomes critical when you are looking for optimized fatigue properties.
Which process is preferred depends on the alloy and what impurities you are concerned with.

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Plymouth Tube

 

[tbuelna]

RedVette-

Here is a good whitepaper from Carpenter that gives a brief overview of their premium alloy melting processes. The paper discusses a pressurized ESR process that deals with the nitrogen issue noted by MagBen. There is also mention of a triple melt process (VIM-ESR-VAR) that uses both ESR and VAR.

Is there a particular alloy and application you had in mind?