Through hardening 42CrMo4. 1

[Roachman]

I have 2 drive pinions which I need to harden. The material is 42CrMo4. One of them has 29 teeth at 4.5 module and a face width of 40mm meshing with an 88 tooth slewing ring. The other has 27 teeth at 4.5 module and 44mm face width meshing with a 68 tooth slewing ring. Both are 20 degree pressure angle.
Can I achieve a contact fatigue limit of 1140 MPa and bending fatigue limit of 450 to 600 MPa by induction hardening the gear tooth faces and bottom as this would give me the desired gear life with this material.
The slewing rings are to be of the same material and the manufacturer informs me that the tooth faces will be at a hardness of 55-63 HRc. Is this degree of hardness capable of being produced by induction hardening alone?

Ref:- thread406-119499

 

[dimjim]

The induction hardening range is certainly
reasonable for that material. Just curious
what the core hardness of this material is?
What depth of hardness to the 50Rc case
depth or 48Rc case depth if it is European.
Get your slewing ring provider to answer the
contact and bending stress questions.
I assume this a slow rpm application.

 

[Roachman]

Yes, it is low speed. The 29t max pinion speed is 50 rpm and the 27t is 30 rpm.

 

[TVP]

According to ISO 6336-5, the contact stress (1140 MPa) and bending stress (450-600 MPa) are well within the limits of a properly induction hardened gear. The surface hardness should be > 54 HRC and the fillets fully hardened. 42CrMo4 is similar to SAE 4140 or 4142, with any of these grades requiring the guaranteed hardenability (+HH for 42CrMo4 according to DIN EN 10083-1 or 4142H according to SAE J1268) in order to always meet the minimum surface hardness of 54 HRC.

 

[dimjim]

My only concern would be that you mention
thru hardening and this may make it susceptable
to brittleness or poor response to shock loading.
So my question about core hardness does not apply.

 

[Roachman]

Thanks for your help fellas!
Should I specify a depth for the induction hardening on these pinions?
If so, what would be the resulting hardness in the core and would this be consistent with the bending fatigue limit I have stated?
I do have the option of ordering slewing rings with a steel spec. of 50Mn which I believe is similar to 1050 and C50.
These would be 20% cheaper.
Would they do the job just as well?
Using the gear calculation software in Inventor10 the values of contact and bending fatigue limits after face hardening of the gear teeth are the same as for 42CrMo4 and the life of the gears for the power they are required to transmit is more than adequate.