CX13VDW vacuum carburizing response
CX13VDW vacuum carburizing response
(OP)
I work at a commercial heat treat company that has an opportunity to vacuum carburize CX13VDW material; we have never worked with this particular chemistry before.
We have established processes to carburize other stainless steels such as Pyrowear 675, and my first process was based on this history. It gave the samples way more case than they needed: targeting around 0.040" the samples ended up with 0.065" effective case depth measured to 50 HRC. Microstructure was martensite with lots of carbides, typical of our past experience with carbuized stainless.
So we get more samples from the potential customer and I dial the carburizing time back. The result is a surface layer of, I think, mostly retained austenite - it has hardness in the 30s HRC. A micrograph taken at 1000x is attached. These samples have been cryo-treated to -110°F.
I would think the retained austenite would be caused by too-high carbon concentrations and perhaps heating it back up and diffusing for a few more hours would allow the case to quench out to mostly martensite. I am really puzzled, though, that the earlier, longer carburizing cycle didn't result in anything like this.
Any thoughts on what the pictured microstructure is, whether a reheat for a few hours would help the surface quench to martensite, and why this shorter cycle turned out so much differently than the longer cycle would be much appreciated.
We have established processes to carburize other stainless steels such as Pyrowear 675, and my first process was based on this history. It gave the samples way more case than they needed: targeting around 0.040" the samples ended up with 0.065" effective case depth measured to 50 HRC. Microstructure was martensite with lots of carbides, typical of our past experience with carbuized stainless.
So we get more samples from the potential customer and I dial the carburizing time back. The result is a surface layer of, I think, mostly retained austenite - it has hardness in the 30s HRC. A micrograph taken at 1000x is attached. These samples have been cryo-treated to -110°F.
I would think the retained austenite would be caused by too-high carbon concentrations and perhaps heating it back up and diffusing for a few more hours would allow the case to quench out to mostly martensite. I am really puzzled, though, that the earlier, longer carburizing cycle didn't result in anything like this.
Any thoughts on what the pictured microstructure is, whether a reheat for a few hours would help the surface quench to martensite, and why this shorter cycle turned out so much differently than the longer cycle would be much appreciated.





RE: CX13VDW vacuum carburizing response
What temp are you using?
My first thought would be to drop the temp.
The V is going into carbides, and some Mo, but you really want to avoid the Cr carbides if you can.
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P.E. Metallurgy, Plymouth Tube
RE: CX13VDW vacuum carburizing response
RE: CX13VDW vacuum carburizing response
An update - I was able to get in contact with our customer's metallurgist who has worked with this material for a while and it turns out the problem is too low of a carbon concentration. This is their explanation:
RE: CX13VDW vacuum carburizing response
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P.E. Metallurgy, Plymouth Tube
RE: CX13VDW vacuum carburizing response
http://sullivansteelservice.com/uploads/Brochure%2...