NITREG®-C is a nitrocarburizing process, based on the proven NITREG® potential-controlled gas nitriding technology, incorporating simultaneous diffusion of carbon and nitrogen into the steel surface.
NITREG®-C is often specified in industrial applications on the merit of its being an environmentally friendly but equivalent alternative to salt bath nitrocarburizing. NITREG®-C conducted in gas atmospheres can be considered a process complementary to NITREG® gas nitriding. The purpose of the treatment is to create a hardened surface layer, enhancing wear and corrosion resistance, or improved fatigue resistance of treated steel or cast iron parts, without distortion of shape or dimensional changes.
It is generally recognized that the Œµ-phase features better wear resistance than . For this reason, engineering drawings sometimes require specified contents of the Œµ phase in the white layer. Therefore, stabilization of ε through NITREG®-C should be viewed as a positive effect. Whenever your nitriding specification calls for a higher ε content, NITREG®-C is the sure answer. Synchro cones, shown in the above photograph, manufactured from a low carbon micro alloyed steel, constitute an application where the major requirement was to have more than 80% of the Œµ phase present in the white layer. Results of X-ray diffraction tests showed the Œµ content to be 97 – 98%.
Examples of Typical Applications
Housings manufactured from 12B10 grade free machining steel, shown on the photograph to the right, required a consistent and uniform white layer of 25 μm (0.0010″) on the entire surface. Uniform nitriding of this part proved to be difficult, due to a surface condition caused by machining. The NITREG®-C process was capable of producing results meeting all specification requirements with excellent uniformity. For those applications where high ε- content, excellent wear resistance and enhanced corrosion resistance are simultaneously required, a combination of NITREG®-C and post-oxidation as in ONC® is the winning solution.
Specifications for gas spring rods made of 1040 steel, shown on the left, required a surface hardness of over 400 HV and a corrosion resistance measured by a minimum of 144 hours in salt-spray per ASTM B117. Combination treatment by NITREG®-C and ONC® resulted in a surface hardness of 590 HV, 400 hours in salt-spray to first corrosion spot as per ASTM B117. Because it is conducted as a fully controlled process, NITREG®-C, with its pronounced effect in promoting the ε phase in the compound layer can bring significant advantages in specific applications.
Advantages of the Nitreg®-C process
- NITREG®-C accelerates formation of the compound (white) layer on low-carbon unalloyed steel.
- NITREG®-C features low operational costs by utilizing more economic gas compositions.
- NITREG®-C increases and stabilizes the ε-phase content in most types of steels.