Plasma (Ion) Nitride
Case & surface hardening · Thermochemical diffusion
Plasma nitriding uses a glow discharge to clean, heat, and diffuse nitrogen into ferrous surfaces.
Reference page — Plasma nitride is not in the instant-quote configurator. Upload the part, name the treatment in the notes with the call-out below, and an engineer quotes it with the part.
Plasma nitride at a glance
Four scores, each 0–100 against every heat treatment in this catalog. Hardness is derived from the HRC target (20 HRC = 0, 70 HRC = 100) — treatments without a hardness target (anneals, stress relief, HIP, cryo) are not rated. Toughness, dimensional stability and cost are FabDigit's engineering assessment.
What is Plasma nitride?
Plasma nitriding uses a glow discharge to clean, heat, and diffuse nitrogen into ferrous surfaces. It offers low distortion, selective masking, and close control of the compound layer for finished precision parts.
How it works
Parts act as the cathode in a low-pressure nitrogen-hydrogen chamber. The applied voltage ionizes the gas; ion bombardment removes surface contamination, heats the load, and supplies active nitrogen. Nitrogen diffuses into ferrite and precipitates nitrides with aluminum, chromium, molybdenum, and vanadium. Gas ratio, pressure, pulse parameters, temperature, and time control the compound layer and diffusion zone. Treatment stays below the steel transformation temperature and uses no quench, so the prior core structure is retained. Mechanical shields or process control can leave selected areas soft without copper plating.
Why specify it
- Produces about 600–1200 HV on common alloy and tool steels
- Permits selective hardening with mechanical masking
- Runs around 400–580 °C without a quench
- Provides about 0.10–0.50 mm nitriding hardness depth with low movement
Where it falls short
- Load arrangement must avoid hollow-cathode overheating in narrow gaps
- Complex deep bores can receive less uniform plasma exposure
- Equipment and cycle cost exceed short FNC cycles
- Stainless surfaces require sputter activation and may lose corrosion performance
The Plasma nitride cycle
Typical furnace parameters from the governing specifications and shop practice; the heat treater sets the exact recipe from the alloy, section size and required result.
| Temperature | 400–580 °C (752–1,076 °F) — Qualified ion-nitriding range; tool and stainless steels often use the lower portion. |
|---|---|
| Soak | 4–40 h — Depth and alloy response govern time; long cases require extended diffusion. |
| Cooling | Still air |
| Atmosphere | Nitrogen / hydrogen plasma |
| Door to door | 8–50 h — Includes evacuation, heating, treatment, and controlled cooling. |
Stages
- 1Harden, temper, and finish machine
- 2Clean and mechanically mask
- 3Evacuate and sputter clean
- 4Ion nitride under pulsed glow discharge
- 5Cool under protective gas
What Plasma nitride does to the part
| Hardness | 58–67 HRC — Approximate equivalent only; specify 600–1200 HV by alloy for acceptance. |
|---|---|
| Case depth | 0.1–0.5 mm — Nitriding hardness depth to core hardness plus 50 HV; state the microhardness load. |
| Toughness | Core properties remain from the prior heat treatment; the compound layer must be limited where impact or rolling fatigue could cause spalling. |
| Distortion | Low risk. No phase-transformation quench is used, but stress relaxation and asymmetric masking can produce small repeatable movement. |
| Surface after treatment | Uniform matte gray; controlled plasma recipes can suppress or tailor the compound layer. |
| Machining sequence | Complete precision machining before treatment; use only light polish or superfinish afterward. |
Specifications for Plasma nitride
The documents a drawing cites to define this treatment. Each links to a page explaining the standard, its classes and the tests it invokes.
| Standard | Role | Classes used | Status |
|---|---|---|---|
Ion Nitriding | Governing | Class 1, Class 2 | Active |
Test and related methods: ASTM E384 (Standard Test Method for Microindentation Hardness of Materials), SAE J423 (Methods of Measuring Case Depth), AMS 2750 (Pyrometry), ASTM E140 (Standard Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness, Scleroscope Hardness, and Leeb Hardness), ISO 15787 (Technical product documentation — Heat-treated ferrous parts — Presentation and indications).
Drawing call-out
ION NITRIDE PER AMS 2759/8 CLASS 1; 900 HV0.5 MIN SURFACE; 0.25–0.40 MM NHD TO CORE + 50 HV ON SURFACES SHOWN; MASK THREADSWhich alloys take Plasma nitride?
Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library. Typical grades: Nitralloy 135M, 4140, 4340, H11, H13, D2, M2, 17-4 PH, 410.
| Material family | Verdict | Notes |
|---|---|---|
| Yes | Dense AM tool and alloy steels can be ion nitrided after core heat treatment.
| |
| Yes | Alloy, tool, and nitriding steels are primary candidates.
| |
| With care | Sintered ferrous porosity changes plasma response and must be qualified. | |
| With care | Martensitic and PH stainless can be treated after corrosion and aging effects are reviewed.
| |
| Limited | Research and medical plasma treatments exist but are outside AMS 2759/8. | |
| Limited | Titanium plasma nitriding exists but is outside AMS 2759/8 steel practice.
| |
| No | This catalog process is ion nitriding of ferrous parts. | |
| No | Brass is outside ion-nitriding steel practice. | |
| No | Bronze is outside ion-nitriding steel practice. | |
| No | Copper alloys do not form the required ferrous nitride case. | |
| No | Magnesium is unsuitable for this steel plasma process. | |
| No | Nickel alloys require separate plasma-surface engineering procedures. | |
| No | Precious metals do not form the intended ferrous nitrided case. | |
| No | Refractory-metal nitriding requires separate high-temperature qualification. | |
| No | Tungsten heavy alloys are not covered by steel ion nitriding. | |
| No | The operating temperature exceeds zinc alloy capability. |
Design rules for Plasma nitride
What to decide on the drawing before the part goes to the heat treater.
- Avoid narrow electrically connected gaps unless the treater validates them.Hollow-cathode discharge can overheat facing surfaces.
- State AMS 2759/8 white-layer class.Class 1 permits 0.013 mm maximum and Class 2 permits 0.025 mm maximum white layer.
- Temper the core above the plasma-nitriding temperature.This preserves prior hardness during the long hold.
- Call out every surface to be nitrided or masked.Selective treatment is a principal advantage but must be inspectable.
- Specify hardness in HV with test load.Thin cases cannot reliably support a Rockwell C impression.
Plasma nitride versus the alternatives
Treatments engineers weigh against Plasma nitride, and when each wins.
| Treatment | Hardness | Toughness | Stability | Cost | Choose it when |
|---|---|---|---|---|---|
Plasma nitride this page | 85 | 52 | 88 | $$$$ | — |
| 85 | 50 | 85 | $$$$ | when dense loads and uniform deep internal surfaces favor controlled ammonia gas | |
| 68 | 55 | 88 | $$$ | when a thinner, faster, lower-cost compound-layer treatment is sufficient |
Cost, lead time and applications
Relative cost
Plasma (Ion) Nitride is a high-cost treatment ($$$$) relative to the other heat treatments in this catalog.
Heat treatment is priced per lot with a furnace minimum. The exact figure appears on the instant quote once the part is uploaded.
Lead time
| Added lead time | 7–14 working days |
|---|---|
| Furnace time | 8–50 h |
What Plasma nitride is used for
- Plastic injection molds
- Extrusion dies
- Precision gears
- Crankshafts
- Valve stems
- AM tool-steel inserts
Plasma nitride — frequently asked
What is the difference between plasma and gas nitriding?
Plasma nitriding uses a low-pressure glow discharge, while gas nitriding dissociates ammonia at the surface. Plasma offers mechanical masking and compound-layer control; gas often suits dense loads and long internal passages.
What temperature does plasma nitriding use?
Qualified cycles commonly fall between about 400 and 580 °C. The setpoint must remain below the prior tempering or aging temperature if core properties are to remain unchanged.
How hard is the plasma-nitrided layer?
Common alloy and tool steels span roughly 600–1200 HV, with Nitralloy and H13 near the upper end. Acceptance should state HV0.5 or another defined load rather than rely on HRC conversion.
How deep is plasma nitriding?
A practical range for many alloy steels is about 0.10–0.50 mm NHD. Depth is measured to core hardness plus 50 HV, not automatically to 50 HRC.
Does plasma nitriding distort precision parts?
Movement is low because there is no austenitizing and no quench. Residual stress can still relax during a 4–40 hour hold, so stress relief before finish machining remains important.
Can plasma nitriding treat stainless steel?
Yes, sputter cleaning can disrupt the passive film, and 410 or 17-4 PH are common candidates. The resulting chromium-nitride precipitation can reduce corrosion resistance, so the requirement must be application-specific.