Carburize or Carbonitride? 1

[mewhg]

I have a smal pin about 4mm dia x 23mm lg made from 1215 steel. The pin needs to have a hard surface for wear resistance and have deformation resistance to hammer blows during installation.

I am planning on case hardening the pin after rough turning then centerless grinding about .1mm off the surface. I hope to end up with about .3mm remaining case and a 55 RC surface (~88 R15-N).

My question, should I specify Carburization or Carbonitriding? I need to use a screw machine steel due to some turned geometry and manufacturing speed.

many thanks
Bill

 

[TVP]

Carbonitriding is a typical operation for small parts like this that have been fabricated from screw machined alloys like SAE 1215. I would start with this before trying anything with carburizing.

 

[metengr]

The decision to either carburize or carbonitride for wear resistance depends on application and cost. The web site below contains some general (unbiased) information regarding practical comparisons between carburizing, carbonitriding and nitriding. The information may be of use to help you evaluate these surface heat treatments.

http://www.treatallmetals.com/capabil.htm

 

[swall]

For your installation process, using "hammer blows", a carburized case might exhibit better resistance to chipping or cracking. Otherwise, I agree with metengr that it's a matter of economics.

 

[mewhg]

Metengr,

Thanks for the link. I had seen it from one of your previous posts and it is a good discussion of the two processes.

My heat treater charges the same for either process. He does say that 12L14 must be Carbonitrited but I didn't know if this was the case with 1215.

I have experience working with carburizing 8620 and 1018. The 1018 takes to carburizing well. Right out of quench its 62RC. I just have not worked much with the screw machine steels.

thanks for the replies,
Bill

 

[limct]

In your case, carbonitriding is prefered, because;
1) lower risk of (small) part distortion as the heating temperature is usually lower than normal carburising.
2) BY nature of the process, it's limited to case depth of about 0.75mm or less, no such limitation exists for carburising
3) carbonitrided surface to softening during tempering is markedly superior.

Best regards,
ct