OSU Engineer
Mechanical
I am going to be making a few outer races for a custom sprag clutch and need some input on how to best achieve the required specs. The attached picture is the model of the outer race shown with an integrated sprocket machined into it. The highlighted blue surface is where the sprags will contact. Per the manufacturer of the sprag clutch, this surface must be 60-64 HRC with an effective hardness depth of .050in. This diameter must also be held to a very tight tolerance. For reference, the diameter is slightly over 2".
The sprocket will be likely changed to an integrated timing pulley in future designs. I do not want to harden the rest of the part and have to worry about distortion and re-machining everything after a heat treatment process. The best solution in my mind seems to be to use something like 8620 and paint the entire part in stop-off paint except the inner rib and have it carburized leaving .010" of grind stock. Then ID grind this diameter and the two adjacent bearing seats as the final step.
Other materials and processes I looked at:
4140 - Does not get hard enough on surface
52100 induction hardened around inner diameter - material is susceptible to forming cracks at inner corners.
Tool steels (A2, O1) - Would still need ground after heat treatment and cannot mask these since they through harden, part would be very brittle.
Nitriding - Cannot achieve deep enough case.
Can anyone offer some input if there's a better way to process this part to minimize distortion, while getting the very hard surface on the inner rib and maintaining core ductility? This isn't a problem for the inner race because I can make that out of a piece of 1566 Case 60 Thomson Shafting, though this custom outer race is a bit more complicated.
Thanks!
The sprocket will be likely changed to an integrated timing pulley in future designs. I do not want to harden the rest of the part and have to worry about distortion and re-machining everything after a heat treatment process. The best solution in my mind seems to be to use something like 8620 and paint the entire part in stop-off paint except the inner rib and have it carburized leaving .010" of grind stock. Then ID grind this diameter and the two adjacent bearing seats as the final step.
Other materials and processes I looked at:
4140 - Does not get hard enough on surface
52100 induction hardened around inner diameter - material is susceptible to forming cracks at inner corners.
Tool steels (A2, O1) - Would still need ground after heat treatment and cannot mask these since they through harden, part would be very brittle.
Nitriding - Cannot achieve deep enough case.
Can anyone offer some input if there's a better way to process this part to minimize distortion, while getting the very hard surface on the inner rib and maintaining core ductility? This isn't a problem for the inner race because I can make that out of a piece of 1566 Case 60 Thomson Shafting, though this custom outer race is a bit more complicated.
Thanks!
