Carburizing Surface hardness 4

[mfgenggear]

We manufacture many aircraft gears which material is AMS6265, AISI 9310 Steel, We do not have in house capability
for Carburizing and Hardening, al of it is farmed out.

We are having a recent problem with a part which
requires .022 efective case depth, 90,5 HR15N at .005 depth
however the verification is done with Vickers,via a cut Met Lab sample Mounted.

The parts are verifing 15N 89 at .002 depth. however it is meeting the hardness at .005 after is ground with 15N superficial.

The procedure as specified per AMS 2759/7 effective hardness
at 50 HRc cutoff.

I have been advised by the supplier that the problem occured because of loss of carbon potential.
This job is run in Endothermic Carburizing Furnace.

what I am aware of is air leak, dew point adjustment, adjustment of gas mixture(methane)

can you please asvise me some finer points in the matter above.

Thanks in advance

 

[dbooker630]

I also agree with TVP and redpicker. It appears that there is some retained austenite, although I have seen much higher amounts than this sample and would not normally take issue with unless <5% RA was specified. A deep freeze (typically -100F, but -50F will work) followed by a temper should get you back into spec. However, if possible you should try to verify surface carbon to support what we think is RA.

 

[mfgenggear]

Thank you all for your comments

The Independent Lab reported this as RA at the surface.

My meeting with the supplier has been postponed till
7-10-08. so all issues will be disscussed & addresed.

Yes this part was deep freeze but this test sample was not.

The surface will be machined off to .005 depth, The RA will be removed at a post operation. parts will be acceptable.

I want to thank you all for the comments and help.
this board is one of the best if not the best.

 

[TVP]

Definitely the best.