Iron is the most commonly used material of construction and
the most commonly found wear metal in used lubricants.
Elemental iron is usually found in the form of cast iron,
carbon steel and high alloy steels. Most machinery cases are
manufactured from cast iron. Most roller bearing rolling
elements and races are manufactured from carbonized steel.
Most gears are also manufactured from carbonized steel. Most
machinery shafts, cams and valves are manufactured from high
alloy or stainless steels. These high alloy steels contain
trace amounts of nickel, chromium, and sometimes titanium.