Trans Shifter, What's it made of?

[Terry, NJ]

I've been working on a transmission , taking a break from the cars.First thing I did was to fix the little ball at the bottom. I welded it and forged it, then I ground, filed and polished it till it worked smoothly. The weld material seemed somewhat resistant to the file, change file! then I notice I putting tracks in the teeth of the file. Then I try to file the handle of the shifter and it seems resistant too. What is that stuff?
Terry