Nitro Carburising

NitroCarburising is variant of nitriding where in carbon is also diffused into the steel for still shallower case depths on low alloyed steels.

NitroCarburizing is a surface hardening process that simultaneously diffuses both nitrogen and carbon into the surface of a metal, typically steel, at relatively low temperatures. This process is a variation of nitriding and is used to improve wear resistance, fatigue strength, and corrosion resistance.
Nitrocarburizing can be performed using various methods, including gas NitroCarburizing.

How It Works

Preparation: The material, typically steel, is cleaned to ensure no contaminants interfere with the process.
Heating: The metal part is heated to temperatures between 930֯F and 1110֯F (500°C and 600°C), depending on the desired depth of the nitrided case.
Diffusion of Nitrogen and Carbon: The component is exposed to a mixture of nitrogen and carbon-based gases (such as ammonia (NH₃) and a carbon-containing gas like methane (CH₄) or propane (C₃H₈)) or (CO2) Nitrogen and carbon atoms diffuse into the surface of the metal, forming a compound layer (consisting of iron nitrides and carbides) and a diffusion zone beneath it.
Compound Layer Formation: The top compound layer is composed of epsilon (ε-Fe₂₋₃N) and gamma- prime (γ’-Fe₄N) phases, which are very hard and wear-resistant.
Beneath this is a diffusion zone where Nitrogen and Carbon are dissolved into the iron matrix, enhancing hardness and toughness.
Quenching (Optional): For some processes, components are quenched after NitroCarburizing to further enhance surface properties, although this is not always necessary.

Benefits

Improved Surface Hardness: The process significantly increases surface hardness, making the metal more resistant to wear and abrasion.
Enhanced Corrosion Resistance: The compound layer formed during nitrocarburizing improves the corrosion resistance of the treated part, making it suitable for components exposed to harsh environments.
Fatigue Resistance: Nitrocarburizing improves the fatigue strength of parts by introducing compressive residual stresses at the surface, which help resist crack formation.
Minimal Distortion: Since nitrocarburizing occurs at relatively low temperatures compared to other heat treatments, it minimizes the risk of distortion or warping of the component.
Shorter Processing Times: Compared to nitriding, nitrocarburizing typically requires shorter cycle times to achieve the desired surface properties.
Cost-Effective: Nitrocarburizing is generally more economical than other surface hardening techniques, as it can be done quickly and requires less expensive equipment.

Typical Materials Used

Low Alloy Steels: Widely used for industrial parts such as gears, shafts, and fasteners.
Carbon Steels: Often used for components that require wear and corrosion resistance without significant structural changes.
Tool Steels: For enhanced wear resistance and longevity in cutting and forming applications.
Cast Iron: Frequently treated for engine components and hydraulic parts.
Stainless Steels: Specific grades can be nitrocarburized to improve wear resistance without compromising corrosion resistance.

Applications

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