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Corr-I-Dur®

Benefits Application & materials Process details

Corr-I-Dur® is a proprietary Bodycote thermochemical treatment for simultaneous improvement of corrosion resistance and wear properties through generating an iron nitride-oxide compound layer.

Benefits

Corr-I-Dur® is favoured for components that are subjected to a corrosive environment in combination with wear. A very successful alternative to hard chromium, electroless nickel and various galvanic coatings through simultaneous improvement of corrosion and wear behaviour; Corr-I-Dur® layers have a very good bonding to the substrate as they are produced in a diffusion process. In many cases parts can be machined with the final dimensions and customers can skip additional steps such as grinding after the Corr-I-Dur® treatment.

Application & materials

Typical applications include brake pistons, ball joints, pump covers, wiper axis, differential axis, selector shafts, bolts, bushings and fastener elements for automotive applications. Also, hydraulic pistons and housings, several axis and shafts for general industry use. Especially, fill chambers and casting dies in aluminium die casting processes get benefit by the low reactivity between molten metal and the Corr-I-Dur® surface.

Corr-I-Dur® can be applied to nearly all plain and low alloyed ferrous materials as case hardening, heat treatable, cold forming and easy machining steel.

Customers value Corr-I-Dur® for its ability to provide superior material properties such as wear and corrosion resistance, combined with cost-effective attributes such as easy machining and forming.

The hardness of the surface increases with the content of hard nitride forming elements such as Chromium, Al, Mo and V. For heavy applications nitriding steels proved their worth due to the high hardness in the diffusion zone.

Tool steels up to 5% Chromium can normally be treated - for higher content of alloying elements please contact our specialists.

Corr-I-Dur® is not recommended for sintered steel with higher porosity resp. low density.

Process details

Corr-I-Dur® is a combination of various low temperature thermochemical process steps, mainly gaseous nitrocarburising and oxidising. In the process, a boundary layer consisting of three zones is produced. The diffusion layer forms the transition to the substrate and consists of interstitially dissolved nitrogen and nitride precipitations which increase the hardness and the fatigue strength of the component. Towards the surface it is followed by the compound layer, a carbonitride mainly of the hexagonal epsilon phase. The Fe3O4 iron oxide (magnetite) in the outer zone takes the effect of a passive layer comparable to the chromium-oxides on corrosion resistant steels. Due to the less metallic character of oxide and compound layer and the high hardness abrasion, adhesion and seizing wear can be distinctly reduced. Corr-I-Dur® has very little effect on distortion and dimensional changes of components compared to higher temperature case hardening processes.