Cryogenic tempering (perhaps not the universally accepted terminology) has been recommended to me as an alternative to induction hardening and/or case carburizing in a pin used in a large thrust bearing (about 3' in diameter). The pins serve as "axles" to hold an array of 40 radially arranged tapered rollers in their assigned places within a cage assy.
The pins are currently 4140 QT (120ksi yield) induction hardened or 8620 case carburized x .55" diameter x 4.5 long. They have acceptable wear life and fatigue life but are expensive to make mainly because they need to be ground after hardening. The 4140 parts have a surface hardness of about 55RC the carburized parts can be a little higher. The parts are press fit into the cage with a substantial interference fit. We hold the diameters to
+/-.0002" by grinding after hardening. If the parts would remain dimensionally stable after cryogenic tempering we have the ability to machine them to that tolerance without grinding in their unhardened state.If I adopt the cryogenic process I will no longer have a surface hardened part but that may be OK.
I have three questions:
1--Is this method suitable for producing a wear resistant surface when subjected to rotary sliding contact in my "axle" application? 2--Is the pin likely to be significantly more brittle? 3--Are the parts likely to be dimensionally stable enough that we can eliminate the grinding after hardening?I have the opinion of engineers from another division of our company that use the process in an application where the workpiece is subjected to heavy impact (it's inside a rock crusher) that feel that it has extended the life of their parts, but their application is different. I am looking for some opinions from persons using this method in applications more similar to my own.
Jon Juhlin snipped-for-privacy@jcieug.com