41L40 for gear
41L40 for gear
(OP)
I changed the material for a gear without appropriate due diligence. When reviewing the project I realized the oversight.
The original gear was 4615 heat treated Rc 55-60, with an unknown process. It is driven by a 4615 carburized idler gear. I changed the material to 41L40 pre-hardened Rc28-32. The original design would run 40 years without noticable wear. The gear is shock loaded. During initial tests the part appears to perform adequately. It is a little difficult to get a handle on the load which will be on this gear as it is driving a cutting wheel.
I fear the gear may fail by wear due to the carburized material being much harder.
It would be convenient to nitride the gear and stay with 41L40. Or should I be considering another material. The gear is part of a long shaft nominally 2" diameter.
I may be in trouble with this customer if I am not able to proactively address this problem if there is one.
The original gear was 4615 heat treated Rc 55-60, with an unknown process. It is driven by a 4615 carburized idler gear. I changed the material to 41L40 pre-hardened Rc28-32. The original design would run 40 years without noticable wear. The gear is shock loaded. During initial tests the part appears to perform adequately. It is a little difficult to get a handle on the load which will be on this gear as it is driving a cutting wheel.
I fear the gear may fail by wear due to the carburized material being much harder.
It would be convenient to nitride the gear and stay with 41L40. Or should I be considering another material. The gear is part of a long shaft nominally 2" diameter.
I may be in trouble with this customer if I am not able to proactively address this problem if there is one.





RE: 41L40 for gear
Without knowing the operating conditions it is impossible to know what problem you may have. The old gearset may have been way over-designed and the 30 Rc replacement might be OK but without all the details it is impossible to say.
RE: 41L40 for gear
Dan
RE: 41L40 for gear
RE: 41L40 for gear
Grade 1 (carburized & hardened to minimum 55 HRC) has an allowable design stress of 180 ksi for contact and 55 ksi for bending. The steel grades listed are 8620 & 9310, but 4615 would be similar for this type of hardness.
4140 that has a core hardness of 300 HB (~ 32 HRC or 145 ksi tensile strength) and nitrided to 84.5 HR15N (~ 48 HRC) has an allowable design stress of 155 ksi contact and 37 ksi in bending. All of this data is based on ANSI/AGMA 2001-C95.
RE: 41L40 for gear
Nitriding is particularly UNsuited for shock loading - it is brittle.
RE: 41L40 for gear