Radical Nitriding
Radical Nitriding Technolog
Radical nitriding is an advanced plasma nitriding method co-developed by Sumitomo Metal Mining Co., Ltd. and Japan Electronic Industry Co., Ltd.
It combines a new theoretical understanding of plasma reactions with decades of heat treatment expertise to achieve highly controlled and stable nitriding results.
Principle and Overview of Radical Nitriding Equipment
Conventional plasma nitriding generates a high-energy plasma through DC glow discharge using a nitrogen-hydrogen gas mixture.
This process heats the workpiece and activates its surface via energetic ion bombardment, while simultaneously forming nitrogen-based radicals that enable nitriding reactions.
In contrast, radical nitriding applies a low-energy plasma generated by carefully controlled glow discharge using an ammonia-hydrogen gas mixture.
Rather than relying on ion bombardment for heating, the workpiece is externally heated, while the highly active radicals formed in the low-density plasma drive the nitriding process.
Figure 1 : Layout of Radical Nitriding Equipment
The radical nitriding system is composed of (1) a vacuum chamber, (2) a vacuum pumping system, (3) a gas control unit, (4) a plasma power supply, (5) an external heating unit, and (6) a cooling unit. The process begins by evacuating the vacuum chamber, then raising the temperature of the workpiece using the external heating unit (7).
After that, a mixture of ammonia and hydrogen gas is introduced into the chamber with the flow rate controlled by a Mass Flow Controller (8). The treatment pressure is maintained at a specified level via an automatic pressure control valve (9). A suitable DC voltage is then applied to the workpiece, forming an optimal plasma condition for radical nitriding. After the nitriding process, the workpiece is cooled using the cooling unit.
Key Advantages of Radical Nitridin
High-Precision Control : Process parameters can be precisely controlled, allowing easy selection of whether to form a compound layer and accurate adjustment of nitriding depth.
Minimal Change in Surface Roughness : Surface finish remains virtually unchanged, even for high-speed tool steels and die steels, maintaining a mirror-like appearance.
Direct Coating Compatibility : Treated surfaces can directly support hard thin films such as TiN via ion plating, without requiring additional surface treatment.
Excellent Edge Retention : The process causes almost no deformation of sharp edges, preserving detailed geometries with high accuracy.
Mixed-Shape Load Processing : Components with varying shapes and weights can be treated together, enabling higher packing efficiency than conventional plasma nitriding.
Oxidation-Free Surface : Vacuum processing results in a clean, oxidation-free surface after treatment.
Low Gas Consumption & Clean Operation : Extremely low gas usage reduces operating costs, while ensuring a safe and clean working environment.