CST's Ni-Surf process for gas nitriding is a contemporary multi-stage procedure for case hardening alloy steels such as 4140 and 4340, special nitriding grades such as Nitralloy 135M, and tool steels such as D-2, H-13, and S-7. It produces a high surface hardness for excellent wear resistance, improved fatigue strength, increased corrosion resistance, and a surface that is resistant to softening from elevated temperatures up to 1000°F.

Since the process is performed at low temperatures and quenching is not required, size change and distortion are very minimal. Parts are therefore core treated and finished machined prior to nitriding with some allowance being made for a slight amount of growth.

The following table lists the typical properties produced by CST's standard Ni-Surf process. Special cycles are employed for deeper case requirements. Parts up to 57 in. diameter or 107 in. can be accommodated. Standard cycles are started daily to ensure excellent turnaround.

Typical Properties Produced By CST's Standard Ni-Surf Process

MATERIAL	CASE DEPTH	SURFACE HARDNESS
4104-4340	0.016-0.019 in.	86-88 HR15N (50-56 HRC)
Nitralloy 135M	0.010-0.013 in.	93-96 HR15N (67-70 HRC)
D-2 Tool Steel	0.008-0.010 in.	92-94 HR15N (64-69 HRC)