Nitrided barrels may be made from 4140 but a nitriding steel, such as Nitralloy 135M enables a better nitrided interior surface to be achieved.

Gas Nitriding

Gas Nitriding is used to create a surface hardness on the barrel. The hard layer of steel will vary in depth from .007” to .015” depending upon the length of the nitriding cycle. The hard layer (usually well above 60 Rc) is achieved by heating the steel in an atmosphere of nitrogen (ammonia gas) at temperatures of 950 to 1050 degrees F. The nitrogen atoms are diffused into the surface of the steel, combining with nitride-forming elements, such as chromium, aluminum, molybdenum, vanadium, tungsten and titanium, to produce a very hard surface, particularly for the first .002” to .005” depth. Nitrided barrels have a very good wear resistance until the surface hardness is worn away. After the surface is worn .007”, wear accelerates and the barrel may quickly be worn to a condition that is beyond repair.

Nitrided barrels are not recommended for use with abrasive or corrosive resins because of their inability to resist wear over an extended time period. Please refer to the Barrel Material Guideline table for further information.

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