Plasma Nitriding Services
Plasma nitriding (ion nitriding) hardens the surface of steel engineering components without a quench step and without meaningful dimensional change. Process temperature 480–520°C. Surface hardness 600–1200 HV. Case depth 0.05–0.6 mm, specified and verified per lot.
1200 HV
1200 HV
0.05–0.6 mm
0.05–0.6 mm
<0.02 mm
<0.02 mm
ISO 9001:2015
ISO 9001:2015
How It Works
Plasma Nitriding in 5 Steps
Loading and Fixturing
Components are cleaned, mechanically masked on surfaces to be protected, and loaded onto batch fixtures designed to ensure uniform plasma exposure — including internal geometries.
Evacuation and Pre-Heating
The furnace vessel is evacuated to process pressure. Components are pre-heated under a hydrogen-rich plasma atmosphere that removes surface oxides and contaminants that would inhibit nitrogen diffusion.
Nitriding Cycle
Gas mixture is adjusted to the specified N₂/H₂ ratio. Temperature (480–520°C), pressure (0.1–10 mbar), and cycle time are held per material grade and required case depth. Plasma penetrates bores, cavities, and complex internal surfaces uniformly.
Controlled Cooling
Furnace is cooled under controlled atmosphere. No quench. Dimensional change is governed by lattice expansion from dissolved nitrogen — predictable, batch-consistent, typically 0.005–0.02 mm on precision components.
Testing and Certification
Vickers microhardness (surface and depth profile), metallographic cross-section, compound layer measurement, and case depth verification per lot. EN 10204 documentation issued per project requirement.
Process Overview
What Is Plasma Nitriding (Ion Nitriding)?
A thermochemical surface engineering process that introduces nitrogen into the surface layer of steel components using a controlled glow discharge plasma in a low-pressure vacuum environment.
Nitrogen reacts with iron and alloying elements — chromium, molybdenum, aluminium, vanadium — to form hard nitride precipitates in the surface layer. This produces two distinct structural zones:
Diffusion Layer (Diffusion Zone)
Zone below the compound layer where nitrogen dissolves into the steel matrix. Introduces compressive residual stresses that improve fatigue strength. Constitutes the measured effective case depth.
Process Parameters
Process Parameters
Compound Layer (White Layer)
Outermost zone, 1–25 µm thick. Iron nitride phases (ε Fe₂₋₃N or γ’ Fe₄N). Provides direct wear resistance. In plasma nitriding, thickness, phase composition, and presence are fully controllable — including suppression to zero. Not achievable in standard gas nitriding.
Engineering Value
Why Engineers Specify Plasma Nitriding
Surface failure accounts for the majority of premature component failures in industrial machinery, tooling, hydraulics, and drivetrain applications. Plasma nitriding addresses all surface failure modes without compromising core toughness.
Surface Hardness & Wear Resistance
600–1200 HV depending on steel grade. Full core toughness preserved. Compound layer harder than electroplated hard chrome on most alloy steel grades — without chrome’s environmental and adhesion issues.
Low Distortion — Critical for Precision
No quench. Dimensional change 0.005–0.02 mm. For shafts, hydraulic rods, gear teeth, and mould cavities where regrinding after surface treatment is not acceptable, low distortion nitriding is the correct specification.
Fatigue Resistance
The diffusion layer introduces compressive residual stresses. Fatigue strength improvements of 15–35% are typical for nitrided steel under rotating bending loads, depending on alloy grade and case depth.
Selective Surface Hardening
Threads, precision bores, sealing faces, and interference fits protected by mechanical masking — no copper plating required. Reproducible and straightforward in plasma nitriding.
Controlled White Layer
Compound layer can be minimised or eliminated by adjusting the N₂/H₂ ratio. Zero white layer when required — for sharp cutting edges or applications where a brittle surface zone is a failure risk. Unique to plasma nitriding.
No Hazardous Waste
N₂ and H₂ in controlled quantities. No cyanide-bearing salts, no hazardous bath disposal, no REACH compliance obligations. The documentable alternative to salt bath nitrocarburizing for supply chains with sustainability reporting requirements.
Plasma nitriding is appropriate
Precision-machined components where post-treatment grinding is not acceptable
Components with internal surfaces, bores, or complex cavities requiring uniform treatment
Selective surface hardening — specific surfaces treated, others masked
Stainless steel requiring surface hardness without loss of corrosion resistance
Fatigue-critical components requiring compressive residual stress improvement
Specifications requiring controlled or zero white layer
Applications where cyanide-based process chemistry is excluded
Alloy steels: 42CrMo4, 31CrMoV9, 34CrNiMo6, H13, D2
Consider a different process
❌ Plain carbon steel (C45): lack of Cr/Mo/Al/V limits achievable hardness to 300–450 HV — insufficient for demanding wear applications. Change the steel grade.
❌ Case depth above 0.8 mm: gas nitriding at higher temperature is typically more appropriate.
❌ Non-ferrous alloys: Al, Ti, Cu, Ni-based alloys require different surface engineering technologies.
❌ Very thick compound layer for corrosion only: salt bath nitrocarburizing + oxidation may be preferred.
❌ Surface hardness above 1200 HV: PVD (TiN, TiAlN) or CVD required.
Process Variant
Plasma Nitrocarburizing
When sliding contact requires a different compound layer phase.
Plasma nitrocarburizing introduces both nitrogen and carbon simultaneously into the compound layer, shifting phase composition from γ’ (Fe₄N) toward ε (Fe₂₋₃(N,C)). The epsilon compound layer has a lower coefficient of friction and better resistance to adhesive wear under sliding and mixed-lubrication conditions.
Specify plasma nitrocarburizing when:
- Component operates under sliding, rotating, or reciprocating contact (control spools, actuator pistons, crankshaft journals)
- Friction reduction is as important as surface hardness
- High-frequency oscillating motion creates fretting conditions
- Compound layer corrosion resistance is part of the specification
- Lubricated sliding contact under mixed lubrication regime
Plasma Nitriding vs. Nitrocarburizing
Selection Guide
Applications
Industries and Typical Components
Industrial Machinery
- Nitriding gears and spline shafts — 42CrMo4 at 650–750 HV
- Cams, bearing housings, wear plates
- Hydraulic rods and pistons — dimensional change <0.02 mm
Hydraulics & Valves
- Control spools and actuator rods — plasma nitrocarburizing for sliding contact
- Valve seats and pump components
- Precise bore geometry maintained post-treatment
Tool and Die
- H13 die casting inserts — thermal fatigue and adhesive wear resistance
- D2 cold work dies — 1000–1200 HV on forming and cutting surfaces
- Extrusion screws, moulds — selective masking on ejector pin bores
Automotive
- Camshafts and crankshafts — fatigue + wear combined specification
- Transmission gears — nitriding gears in 42CrMo4 or 16MnCr5
- Injection components — tight dimensional tolerances maintained
Food Processing & Chemical
- Austenitic stainless — S-phase treatment for surface hardness without loss of corrosion resistance
- 316L components: 900–1300 HV, corrosion resistance preserved
- Hygiene-compatible process — no cyanide-bearing chemistry
Oil & Gas / Defence
- Valve bodies, pump impellers, flow control — 316L S-phase and alloy steel
- Structural alloy steel components with documented EN 10204 traceability
- Investment cast components requiring integrated casting + nitriding supply chain
Why Plasmaterm
Why Choose Plasmaterm for Contract Plasma Nitriding
Plasmaterm has applied plasma nitriding since 1965, when the organisation was founded as a materials science and plasma surface engineering research institute — before ion nitriding was an established industrial process. Diagnostic approach of a research institution, not a production-only operation.
Integrated Supply Chain
- Investment casting and plasma nitriding in the same facility — no inter-supplier handover
- One ISO 9001:2015 quality management system covers both casting and surface treatment
- One EN 10204 traceability chain from melt to surface-treated, certified component
- No traceability gap at the casting-to-nitriding interface — because there is no interface
- One purchase order, one contact, one quality record
Testing & Traceability
- In-house metallographic laboratory — compound layer, diffusion layer, case depth per lot
- Vickers microhardness — surface hardness and depth profile per treated lot
- OES spectrometry (Foundry Master Smart) — material composition verified before processing
- EN 10204 certificate types 2.1, 2.2, 3.1, 3.2 available
- ISO 9001:2015 — valid to June 2027
Process Capability
- Parameters developed per material grade, component geometry, and surface specification — not from a standard table
- Controlled white layer and diffusion-zone-only cycles available
- S-phase treatment for stainless steel — in-house, not subcontracted
- Selective surface hardening by mechanical masking — engineered per component
- Plasma nitrocarburizing alongside plasma nitriding — process selected per application requirement
FAQ
What is the difference between plasma nitriding and gas nitriding?
Gas nitriding uses dissociated ammonia at 480–540°C. White layer formation is inherent and difficult to suppress. Selective treatment requires copper plating of masked areas. Plasma nitriding (ion nitriding) operates at 480–520°C in a vacuum environment with independently controllable parameters — temperature, gas mixture, pressure, current density — enabling:
- Controlled white layer, including zero white layer
- Mechanical masking without copper plating
- Effective uniform treatment of internal geometries and bores
- Lower distortion than gas nitriding at equivalent case depths
For precision engineering components, plasma nitriding delivers greater process control and lower dimensional change.
What surface hardness can plasma nitriding achieve?
600–1200 HV depending on steel grade:
- Dedicated nitriding steels (31CrMoV9, 38CrMoAl): 950–1200 HV
- Alloy engineering steel — nitriding 42CrMo4: 650–800 HV
- Tool steels H13 / D2: 900–1200 HV
- Stainless steel S-phase (1.4301 / 1.4404): 900–1300 HV
- Plain carbon steel C45: 300–450 HV — insufficient for demanding wear applications
What case depth can be achieved?
Total case depth 0.05–0.6 mm. Effective case depth (to 550 HV threshold) typically 0.1–0.4 mm on alloy steel grades at standard parameters. Compound layer 1–25 µm, measured separately from the diffusion layer. Both specified and verified per lot with metallographic cross-section documentation.
What is the compound layer (white layer) and when should it be suppressed?
The compound layer is the outermost nitrided zone, 1–25 µm thick, consisting of iron nitride phases. It provides direct wear resistance. In most wear applications a compound layer is beneficial. Suppress it when:
- Sharp cutting edges under bending load — brittle surface zone is a failure risk
- Fatigue-critical components where compound layer crack initiation is a concern
- Subsequent coating or joining operations where compound layer adhesion would be an issue
Reliable white layer control — including zero white layer — is available through plasma nitriding. Not achievable in gas nitriding or salt bath processes without process modifications.
How do I submit a project for contract plasma nitriding?
Send the following:
- Drawing (PDF)
- Material grade (EN/DIN or AISI designation)
- Surface hardness and case depth requirement
- Masked surfaces or selective treatment requirements