8620 surface perlite
8620 surface perlite
(OP)
Hi,
I realy have hard time dealing with surface perlite for carburized 8620. I'm using endo and the case depth I'm aiming for is .030". I'm looking for any tips to reduce surface perlite/bainite.
Thank you,
T
I realy have hard time dealing with surface perlite for carburized 8620. I'm using endo and the case depth I'm aiming for is .030". I'm looking for any tips to reduce surface perlite/bainite.
Thank you,
T





RE: 8620 surface perlite
Could you please describe your carburizing procedure in some detail? This way proper help can be provided. In the meantime, even if you are familiar with heat treatment of steels, the information below might be of help to you;
http://
RE: 8620 surface perlite
RE: 8620 surface perlite
Check your carbon content in the case. Running a round coupon and collecting turnings at 0.005" depth works well. With 8620, I'm guessing you'd need over 0.60%C to eliminate the pearlite. I'd be suprised if your getting over 0.40% at 0.005" deep. I'm guessing you'll need longer time at a lower carbon potential to acheive your goals.
rp
RE: 8620 surface perlite
Boost:
Temp - 1700 deg. F, Carbon potential - 1.20 to 1.25
Time - 3:15 hours
Diffuse:
Drop potential to 0.90 to 0.95%.
Time - 2:00 hours.
Equalize:
Drop temperature to 1625 deg.C or less for distortion control.
Soak for 30 minutes and qench.
You can check the carbon content as recommended in the previous post.
You can also go to higher carburizing temperature (1750 deg. F) and reduce the cycle time. You have few options to look at and I hope this helps.
RE: 8620 surface perlite
RE: 8620 surface perlite
Yes, non-martensitic transformation products (NMPT) like bainite and pearlite occur in the surface layer when the atmosphere contains oxygen. Intergranular oxidation and decarburization are other potential problems. It sounds like you need to better control the atmosphere. Do you have a good reference on heat treating, such as Carburizing: Microstructures and Properties by Geofrrey Parrish (published by ASM International)? There is even specific information on lean-alloys like SAE 8620 and the problem of NMTPs.