Cylinder Barrel
Cylinder barrel is made of a steel alloy forging with the inner surface hardened to resist wear of the piston and the piston rings which bear against it.
Hardening is usually done by exposing the steel to ammonia or cyanide gas while the
steel is very hot. The steel soaks up nitrogen from the gas,which forms iron nitrides on the exposed surface. As a result of this process, the metal is said to be nitrided.
Nitriding only penetrates into the barrel surface a few thousands of an inch. As the cylinder barrels wear due to use, they can be repaired by chroming. This is a process that plates chromium on the surface of the cylinder barrel and brings it back to new standard dimensions.
Chromium-plated cylinders should use cast iron rings. Honing the cylinder walls is a process that brings it to the correct dimensions and provides crosshatch pattern for seating the piston rings during engine break-in.
Cylinder barrels are choked at the top, or they are smaller in diameter to allow for heat expansion and wear.
Barrel may has threads on the outside surface at one end so that it can be screwed into the cylinder head.
Cooling fins are machined as an integral part of the barrel and have limits on repair and service.
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