What are most gears made from?

[aceofspades25]

I was wondering what most gears are made from? I am getting ready to start a new job where I will be working with gears. I will be grinding them. I am also in school and I have to do a research paper on a metal of my choice. I figured I might as well research the metal I will be working with so I will now more about it.

Thanks

[MBG]

I know gears that are made out of aluminum t6. I hard coat anodize them for strength and wear resistance.

[BillPSu]

Gears are made from everything from plastic to hardened steel. Carburized (Case)hardened steel gears are made from typically 8620 which creates a hard case with a ductile soft core. Through hardened gears are made from many different steels but 4140 is a common material. The material used is based on several factors including weight, load being carried, speed, life expectancy, environment, design safety factor, machinability, and tolerance of finish gear. This is not an all inclusive list but gives you some idea of the design parameters which need to be investigated before a material is specified for a gear.

[aceofspades25]

What about gears made for high torque? 4140?
The company is Rockwell Automation if this helps.

[machiner11]

BillPsu...Excellent answer and very true. Rockwell probably uses many materials for gears depending exactly as BillPsu stated, on the application. Could be anything, 8620, 4140, 4150