Special Grades 135 Modified

Principal Design Features

Nitralloy 135 Modified, as it is commonly known, is a low alloy nitriding steel grade with moderate hardenability. It was designed to provide a high case hardness and maintain its core strength during nitriding. VAC-ARC and VIM-VAR melting procedures tend to yield the most prefered ingot solidification, as well as superior cleanliness.


Aircraft applications, including gears, crankshafts, cams and bolts.

Heat Treatment

Normalize by heating to 1800 F and hold for 1 to 4 hours, followed by air cooling. Austenitize by heating to 1700-1750 F for 1/2 hour per inch of cross section and quench in oil or water.


Heat evenly to 2000-2025 F. Do not work below 1700F. Forgings should be air cooled.


Heat to 1700 F and slow cool or subcritical anneal at 1250-1300F.


Heat to 1000-1300 F depending on the desired end hardness. Temper material one hour for each inch of thickness


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