But while conventional gas nitriding has worked reliably for decades, plasma nitriding — also known as ion nitriding — is gaining increasing importance. The reason: alongside its technical advantages, its energy balance and environmental impact speak clearly in favour of the more modern process.
In conventional gas nitriding, steel components are placed in an ammonia-containing atmosphere at temperatures between 480 °C and 580 °C. Nitrogen thermally diffuses into the component surface, forming a hard surface layer. The process is robust and well-controllable, but generates considerable quantities of process gas — and thus emissions. Ammonia and its decomposition products, including NOx and CO₂, must be treated in complex aftertreatment systems or incinerated.
In plasma nitriding, by contrast, the component surface is activated by an electrical glow discharge. In a low-pressure reaction vessel, nitrogen and hydrogen ions are accelerated onto the workpiece by an electric field. The energy of the impacting ions heats the component directly while simultaneously driving nitrogen diffusion.
Emissions: Dramatic Differences
The emissions comparison between the two processes is unambiguous. Gas nitriding systems produce approximately 2,700 times as much CO and CO₂ and around 5,500 times as much NOx as comparable plasma nitriding systems during operation. These figures are not theoretical model values, but the result of comprehensive life cycle analyses (LCA) that compared both processes using the CML-2001 method across all environmental impact categories — from global warming potential to acidification to human toxicity. Plasma nitriding performs considerably better in virtually all categories.
Resource Consumption: Less Gas, Less Energy
The difference in process gas consumption is particularly striking. A typical component requires approximately 90 m³ of process gas in a gas nitriding system; the comparable plasma nitriding system manages with around 5 m³ — a factor of roughly 15 in favour of the plasma process. Since the process operates under vacuum, the continuous gas flow required in atmospheric gas nitriding to maintain the reactive atmosphere is eliminated entirely.
A similar picture emerges for primary energy consumption: plasma nitriding reduces energy use by approximately 56 % compared to gas nitriding. This is explained by the fundamentally different heating principle: while gas nitriding requires the entire furnace chamber and atmosphere to be heated, plasma nitriding heats the component surface directly. Around 40 % of electricity consumption is attributable to the heating phase alone; during the actual nitriding process, the plasma itself takes over the majority of the required heating output.
Not Without Weaknesses
Despite its compelling sustainability record, a one-sided comparison falls short. Modern, highly developed gas nitriding systems have made significant advances in recent years. With precise Kp value management and optimised purging phases, they can close the gap considerably in terms of gas consumption and process time — and sometimes offer shorter amortisation periods than the more capital-intensive plasma systems, particularly for simpler component geometries and large batches.
There are also process-specific limitations of the plasma method: complex cavity geometries, deep bores and sharp component edges can lead to inhomogeneous layer thicknesses or edge overheating if the process is not managed carefully. These challenges are, however, increasingly addressable through the so-called Active Screen technology, in which a metal cage placed upstream decouples plasma generation from the actual workpiece.
Sustainability as a Competitive Factor
What was once a technical side consideration is now becoming a tangible business argument: with the growing importance of CO₂ footprints, supply chain transparency and ESG criteria in procurement, the sustainability data of manufacturing processes are coming into sharper focus. Plasma nitriding offers a clear advantage here — not only because of its lower emissions, but also because it operates entirely without chemicals and generates no wastewater issues, such as those associated with salt bath nitriding.
For companies pursuing sustainability certifications or acting as suppliers to the automotive and aerospace industries, the choice of nitriding process can thus become a measurable differentiating factor.
Conclusion
Plasma nitriding is not automatically the right choice for every application — but it is the more sustainable process. The drastically lower process gas consumption, reduced emission levels and lower energy use make it the superior option whenever ecological metrics play a role. For industry, this means: those who invest in modern plasma systems today are securing not only technological flexibility, but also a solid foundation for the sustainability reports of tomorrow.
