The planet gear teeth and bearing outer race surface are case hardened by carburizing. The spherical bearing rollers and inner race are through hardened bearing steel. The cage is quenched and tempered alloy steel with a coating like silver electroplating.
The article linked by turboshaft was very interesting. Learned quite a bit about actual maintenance procedures used by commercial operators.
The following comment caught my attention, "Although the particle was removed from the epicyclic chip detector, maintenance personnel did not remove the epicyclic module or recover any particles that might have accumulated on the magnets that were part of the gearbox separator plate." This is something I had asked about in previous posts. Whether the gearbox separator plate arrangement was trapping ferrous debris from the epicyclic stages contained in the return oil flow.