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Ion Nitride brittleness, corrosion

I have a hot pressing die that uses a 3/8" thick by 3" dia disk for a punch liner. I have tried ion nitrided 17-4, but the edges crack to easily. Is a material like H-13 more resistant to this, even though the hardness is similar when nitride. Also would the corrosion resistance be similar. I now the H-13 corrosion resistance will increase, while the 17-4 decreases, but I do not know by how much. I am pressing hard, caustic mineral salts under argon.

Thank you,

Carl Marters
- Westminster, California
2003

You don't specify what kind of salts you are grinding or at what temperature, but here goes a hint. Try a punch made of hardened H-13 and coated with a "sprayed and fused" 0.5mm (0.020") thick layer of a high nickel or cobalt hard alloy like Stellite or Colmonoy ground to shape. This will surely last longer. Shops doing work for the glass molds have known these tricks for long.

Guillermo Marrufo
Monterrey, NL, Mexico
2003

I am pressing at 700f Salts include lithium and potassium chlorides, as well as mineral content like magnesium oxide, cobalt, iron disulfide... I have tried hastiloys and cobalt alloys including stellites, ultimet, 6b alloys, molly, tungsten. I am attempting to find a less expensive material. A standard tool steel with a treatment would drastically reduce time and cost of producing tooling.

Carl Matters
- Westminster, California
2003

Carl,
What you are trying to do is to find a very complex combination where you optimize everything: cost, corrosion resistance, abrasion resistance and fatigue resistance. This is a matter of a detailed study of your case (not very likely to be solved via a net search).

Best luck,

Guillermo Marrufo
Monterrey, NL, Mexico
2003