carburizing vs carbides check location

[MATTHEWZHI]

Hello every expert:

A lot of specifications, such as AMS 2759/7 state to check case depth at pitch diameter, or far away from canners etc. But for carbide check, they never mention check locations (I assume specifications require to check everywhere). Sometimes carbides exceed the limits from specifications, especially at gear or spline tooth edges. So what is your opinion?

Thanks,

Matthew

 

[redpicker]

You should be checking for carbides in the carburized case, that is where they are likely to form. If they exceed the speciifcation limits anywhere in the case, the parts are rejectable.

rp

 

[MATTHEWZHI]

Hi Redpicker,

Thank you for your quick response. Do you know any specificaiton specify that?

Thanks,

Matthew

 

[redpicker]

No, when I was involved with carburizing, we were processing our own parts and only worked to our internal specifications, which simply stated that no carbide network was acceptable in the case. Since the Metallurgy department wrote the specification and also evaluated the coupons, we were never unsure of what our requirements were.

rp

 

[mfgenggear]

The microstructure is verified at the gear tooth & and any other surface specified to be carburized.

a sample is section and that sample is to represent the parts per heat lot\load.

 

[dbooker630]

It depends on the application. Some specs will allow discrete peppery carbides, but not necessarily if the carbides are dog bone-shaped.

Network carbides have always been unacceptable in my experience. The fact that you have any carbides at all suggest a problem with furnace carbon potential.