Austempered ductile iron

[Pville]

I am looking for another an alternative to austempered ductile iron. The geometry requires that the part be cast. We currently use ASTM A536 Grade 80-55-06 with an austemper heat treatment to achieve 385-470 BHN. Because these parts are in moving contact with each other, wear is significant. Does anyone have a suggestion for an improved material.

 

[aviteri]

I guess ductile iron ( ductle cast )is not the same that steel, you won't ever get austenite in a iron.
But i don´t speak english very well so, maybe i did't understand your question

 

[TVP]

aviteri,

Austempering a type of heat treatment, suitable for both steels and cast irons. Use the following link for more information:

http://www.ductile.org/didata/Section4/4intro.htm

 

[arunmrao]

Yes you can use casting in steel of 4330 grade instead of ADI.This you can suitably heat treat to achieve the desired mechanical properties.

 

[Carburize]

Why do you want an alternative? Is the existing part failing or is it too expensive?

 

[Pville]

Carburize:
Actually, both. Austempering adds a significant cost, however I currently reach only 400 hours of operation before the 4mm treatment depth is exceeded. I was hoping to find a material that may be of approximately the same cost, yet obtain improved wear characteristics. I realize the at 477 BHN, we're getting fairly high hardness and a point of diminsishing returns relative to cost may occur with a significant improvement above the existing properties.
Thanks.

 

[Carburize]

Have you considered a cast carburized part?
Companies like Falk make cast carburized gears - this would give you the ability to manufacture the part plus the carburized case will be around 60 Rc

 

[arunmrao]

What is castt carburize? Does it mean you get a case in as cast condition? If conventional case hardening is acceptable then 8620 grade can also be considered. earlier I had suggested a oil quench and temper cycle(through hardenenig).

 

[Carburize]

I am suggesting that the part can be cast from an appropriate alloy then carburized in the wear areas as an alternative to austempering.
The original question indicated that casting is the only viable route to produce the desired shape and my follow up question was to try to see if the problems were associated with wear or some other failure mechanism. It appears that wear is the issue so carburizing the affected surfaces may help to extend the life of the parts.

 

[GRoberts]

4330 & 4340 can be cast and heat treated to tensile strengths of 210 ksi. The typical brinell hardness should be approximately 450. ASTM A958 & A915 are good references.

 

[jkeough]

I gather from the conversation that the Austempered Ductile Iron parts that you are using are not through hardened. ADI is a through hardening process. If the parts are only hardened to some skin depth then either the process was done incorrectly OR the alloy in the ductile iron was insufficient. Furthermore, there is another grade of ADI that is even harder and more wear resistant than the one you have chosen. That grade, 230-185-00 would give you a hardness in excess of 450HBW. Another option in the ADI family would be Carbidic ADI which is competitive with 18Cr white irons. Please visit

http://www.appliedprocess.com

and contact us if you wish to know more or to discuss your specific application.