surface treatment in plasma
Plasma Nitriding

A process that increases surface hardness and effectively protects against wear: With plasma nitriding, we offer a high-performance treatment for mechanically stressed metal components.

Our extensive capacities and short lead times allow us to process all orders quickly and efficiently. Every day several processes start – so we are able to quickly implement even short-term requests at any time.

Single part, series or particularly large parts plasma nitriding? No problem, we will implement your order quickly, reliably and in the highest quality.

 

Plasma nitriding: the process

Plasma nitriding (also known as ionitriding, pulse plasma nitriding, as well as cold nitriding or plasma hardening) is a thermochemical heat treatment process that is used to increase the reliability and wear resistance of mechanically stressed metal components. Fatigue strength as well as corrosion protection of materials are improved by surface treatment in a particularly gentle way. Under the influence of heat, plasma nitriding causes a chemical transformation of the surface layer by diffusion of nitrogen, which forms nitrides together with the material of the treated material. This leads to increased surface hardness and significantly improved resistance to wear.

Compared to conventional hardening processes, the workpieces are treated at significantly lower temperatures, which ensures high dimensional accuracy in this type of heat treatment. Since, as a consequence, a costly reworking of the workpieces in the surface hardened condition is no longer necessary or can be reduced to a minimum, plasma nitriding allows additional cost savings to be realized within the process chain.

The material to be treated can often be manufactured to final dimensions in the soft state and can be finished after heat treatment in the plasma with little or no reworking. Furthermore, very low tempered, heat- treated steels can be treated without loss of core strength.

In principle, nitriding is possible with various processes. Well known besides plasma nitriding are bath nitriding and gas nitriding. Among the hardening processes, plasma nitriding has a special position due to its reproducibility, environmental compatibility and energy efficiency.

Plasma nitriding: the advantages

  • low process temperatures
  • low-distortion process
  • Minimization or elimination of rework
  • Final cleaning and surface activation of components in plasma
  • good treatability of high-alloy steels and stainless steel
  • Layer structure can be adapted to the stress
  • Layers are less brittle and porous than with gas and bath nitriding
  • shorter treatment times than (with the) gas nitriding
  • no subsequent cleaning necessary

By controlling the layer structure in a targeted manner, plasma nitriding allows the treatment result to be adapted advantageously to the stress. Compared to conventional hardening processes, heat treatment in plasma takes place at significantly lower temperatures. Mechanical post-processing is often no longer necessary due to the resulting minimized distortion.

Physical principles of plasma nitriding

The physical principles of plasma nitriding lead to the characteristic features of the process and the necessary plant technology:

Plasma nitriding is a vacuum-supported process. The treated workpieces form the cathode, the furnace wall the anode. After evacuation of the loaded recipient, an electric field is applied between the charge and the furnace wall. The supplied treatment gas splits up in the electric field and is ionized. A conductive gas is formed – the plasma. The nitrogen ions contained in it are accelerated due to the current flow in the direction of the cathode and hit the workpiece surfaces with high energy. This leads to:

  • Fine cleaning of the surfaces by sputtering off foreign atoms
  • Dissolving of passive layers (e.g. on stainless steels or stainless steel and titanium)
  • Activation of the surface
  • Heating of the furnace charge to be nitrided
  • Diffusion of the nitrogen into the workpiece surface

When the treatment temperature is reached, the holding time begins. This depends on the type of material and the desired nitriding hardness depth. Usual holding times for plasma nitriding are 12-50 hours. Compared to gas nitriding, plasma nitriding requires only about half the holding time.

After the corresponding treatment time, pressure equalization is achieved by flooding with a gas. Afterwards the batch cools down in a controlled manner and the finished workpieces can be removed at low temperature.

 

The nitriding layer and its function

The nitriding layer consists of the outer bonding layer (VS) and the diffusion layer (DS) underneath. The compound layer is composed of iron nitrides – the nitrogen-rich ε nitride Fe2-3N and the iron-rich γ`-Nitride Fe4N. In comparison to gas nitriding, the compound layer produced by plasma nitriding is more compact, has fewer pores and therefore has better layer properties.

Below the VS is the diffusion zone (DS), which is composed of the base material with precipitated nitrides. The more nitride-forming elements are present in the steel, the greater the attainable surface hardness. This explains why unalloyed steels only achieve surface hardnesses of 250-300 HV, low-alloy steels 600-700 HV and nitriding and high-alloy steels 800-1200 HV.

The characteristic value nitriding depth NHT is defined as the edge distance at which core hardness +50 HV is present (according to DIN50190 Part 3). Usual NHT are:

  • up to 0.8 mm for unalloyed and low-alloy steels
  • up to 0.15 mm for high-alloy steels and stainless steel

The depth that can be reached and the time in which it can be reached is largely determined by the material used, the treatment temperature and the treatment time.

If particularly thick compound layers are required, plasma nitrocarburizing is recommended as an alternative to plasma nitriding. To increase the corrosion resistance of low and medium alloyed materials, there is also the possibility of post-oxidation. With the help of this additional step, the corrosion protection can be further increased after plasma nitriding.

 

Nitridable steels and treatment results after plasma nitriding

The following treatment results of plasma nitriding refer to standard and long-term treatments and frequently used materials. A higher or lower nitriding hardness depth (NHT) and compound layer thickness (VS) can be achieved by special treatments.

In general, any steel can be nitrided. We would be pleased to advise you on the possibilities and individual advantages – please contact us!

Nitrierstähle

Material Material number Hardness HV 1 NHT in mm VS in µm
32 CrMoV 12-10 1.7765 750 – 1.000 0,2 – 0,6 4 – 15
34 CrAl 6 1.8504 900 – 1.200 0,2 – 0,5 4 – 10
34 CrAl S 5 1.8506 900 – 1.200 0,2 – 0,6 4 – 10
34 CrAlMo 5 1.8507 900 – 1.200 0,2 – 0,5 4 – 10
41 CrAlMo 7 1.8509 800 – 1.000 0,2 – 0,5 4 – 10
31 CrMo 12 1.8515 800 – 1.100 0,2 – 0,5 4 – 15
31 CrMoV 9 1.8519 750 – 1.000 0,2 – 0,5 4 – 15
31 CrAlV 79 1.8523 900 – 1.250 0,2 – 0,6 4 – 10
34 CrAlNi 7 1.8550 900 – 1.250 0,2 – 0,6 4 – 15

Einsatzstähle

Material Material number Hardness HV 1 NHT in mm VS in µm
C 15 1.0401 300 – 450 0,2 – 0,6 4 – 15
C15 E / Ck 15 1.1141 250 – 350 0,2 – 0,6 4 – 15
21 MnCr 5 1.2162 600 – 750 0,3 – 0,6 4 – 15
14 NiCr 15 1.5752 500 – 650 0,2 – 0,6 4 – 8
15 CrNi 6 1.5919 500 – 750 0,2 – 0,8 4 – 8
20 NiCrMo 2-2 1.6523 650 – 700 0,2 – 0,6 4 – 8
18 CrNiMo 7-6 1.6587 600 – 700 0,2 – 0,6 4 – 8
16 MnCr 5 1.7131 600 – 750 0,2 – 0,8 4 – 15
16 MnCrS 5 1.7139 600 – 750 0,2 – 0,8 4 – 15
20 MnCr 5 1.7147 600 – 800 0,2 – 0,8 4 – 15
20 CrMo 5 1.7264 850 – 950 0,2 – 0,8 4 – 15

Vergütungsstähle

Material Material number Hardness HV 1 NHT in mm VS in µm
C 30 E 1.1178 300 – 450 0,2 – 0,6 4 – 15
C 35 E 1.1181 300 – 500 0,2 – 0,6 4 – 15
C 45 E / Ck 45 1.1191 300 – 550 0,2 – 0,6 4 – 15
C 60 E / Ck 60 1.1221 300 – 550 0,2 – 0,6 4 – 15
40 CrMnMo 7 1.2311 700 – 850 0,2 – 0,6 4 – 15
40 CrMnMoS 8-6 1.2312 700 – 850 0,2 – 0,6 4 – 15
45 NiCr 6 1.2710 600 -800 0,2 – 0,5 4 – 8
55 NiCrMoV 6 1.2713 600 – 700 0,2 – 0,6 4 – 8
30 CrNiMo 8 1.6580 600 – 800 0,2 – 0,5 3 – 10
34 CrNiMo 6 1.6582 600 – 800 0,2 – 0,5 3 – 10
34 Cr 4 1.7033 500 – 600 0,2 – 0,5 4 – 15
25 CrMo 4 1.7218 600 – 700 0,2 – 0,5 4 – 15
34 CrMo 4 1.7220 500 – 600 0,2 – 0,5 4 – 15
42 CrMo 4 1.7225 600 – 750 0,2 – 0,5 4 – 15
30 CrMoV 9 1.7707 850 – 950 0,2 – 0,6 4 – 15
39 CrMoV 13-9 1.8523 800 – 950 0,2 – 0,5 4 – 8
Toolox33, SP 300 siehe 1.2312      
Toolox 44   800 – 1.000 0,2 – 0,6 4 – 8
ETG® 100 1.8523 400 – 650 0,2 – 0,6 4 – 8

Baustahl

Material Material number Hardness HV 1 NHT in mm VS in µm
S 235 JR 1.0037 250 – 400 0,2 – 0,6 4 – 10
S 235 1.0038 200 – 350 0,2 – 0,6 4 – 10
E 335 1.0060 300 – 550 0,2 – 0,6 4 – 10
S 235 J2G3 1.0116 350 – 400 0,2 – 0,6 4 – 10
S 355 J2+N 1.0570 300 – 550 0,2 – 0,6 4 – 10
S 355 J2H 1.0576 300 – 550 0,2 – 0,6 4 – 10

Werkzeugstahl, unlegiert

Material Material number Hardness HV 1 NHT in mm VS in µm
C 105 W 1 1.1545 550 – 650 0,2 – 0,8 4 – 8
C 80 W 2 1.1625 550 – 650 0,2 – 0,8 4 – 8

Warmarbeitsstähle

Material Material number Hardness HV 1 NHT in mm VS in µm
X 38 CrMoV 5 1 1.2343 900 – 1.250 0,2 – 0,4 4 – 8
X 40 CrMoV 5 1 1.2344 900 – 1.250 0,2 – 0,4 4 – 8
X 32 CrMoV 3 3 1.2365 800 – 1.000 0,2 – 0,4 4 – 8
X 3 NiCoMoTi 18-9-5 1.2709 800 – 1.200 0,15 – 0,3 2 – 4
X 15 CrCoMoV 10-10-5 1.2886 1.000 – 1.200 0,15 – 0,3 2 – 4

Kaltarbeitsstähle

Material Material number Hardness HV 1 NHT in mm VS in µm
X 210 Cr 12 1.2080 900 – 1.200 0,1 – 0,15 2 – 4
62 SiMNCr 5 1.2101 500 – 600 0,3 – 0,6 4 – 8
X 165 CrV 12 1.2201 1.000 – 1.200 0,1 – 0,4 2 – 4
115 CrV 3 1.2210 350 – 500 0,3 – 0,4 4 – 8
26 CrMoV 9 1.2307 850 – 950 0,1 – 0,4 4 – 8
X 100 CrMoV 5 1.2363 800 – 1.200 0,1 – 0,4 4 – 8
85 CrMoV 12-6-5 1.2364 950 – 1.200 0,1 – 0,4 4 – 8
X 155 CrVMo 12-1 1.2327 900 – 1.200 0,1 – 0,4 4 – 8
X 210 CrW 12 1.2436 700 – 900 0,15 – 0,3 2 – 4
X 165 CrMoV 12 1.2601 900 – 1.200 0,15 – 0,2 2 – 4
X 60 WCrMoV 9-5 1.2622 800 – 900 0,1 – 0,4 2 – 4
X 45 NiCrMo 4 1.2767 650 – 900 0,15 – 0,5 2 – 4
90 MnCrV 8 1.2842 450 – 650 0,2 – 0,6 4 – 8

Schnellarbeitsstähle

Material Material number Hardness HV 1 NHT in mm VS in µm
S 10-4-3-10 1.3207 1.000 – 1.400 0,05 – 0,25 ≤ 3
S 12-1-1 1.3302 1.200 – 1.400 0,05 – 0,2 ≤ 3
S 6-5-2 1.3343 1.000 – 1.400 0,05 – 0,25 ≤ 3
S 18-0-1 1.3355 1.000 – 1.200 0,05 – 0,2 ≤ 3

Wälzlagerstähle

Material Material number Hardness HV 1 NHT in mm VS in µm
100 MnCrW 4 1.2510 500 – 700 0,2 – 0,3 ≤ 5
100 Cr 6 1.3505 350 – 600 0,2 – 0,3 ≤ 5
X 102 CrMo 17 1.3543 1.000 – 1.200 0,1 – 0,2 ≤ 3

Federstähle

Material Material number Hardness HV 1 NHT in mm VS in µm
C 75 S / Ck 75 1.1248 350 – 550 0,2 – 0,6 4 – 8
60 SiMn 5 1.5142 400 – 600 0,2 – 0,6 4 – 8
67 SiCr 5 1.7103 500 – 650 0,2 – 0,6 4 – 8
50 CrV 4 1.8159 450 – 600 0,2 – 0,6 4 – 8
58 CrV 4 1.8161 450 – 600 0,2- 0,6 4 – 8

Rost- und säurebeständige Stähle

Material Material number Hardness HV 1 NHT in mm
X 40 Cr 14 1.2083 1.000 – 1.200 0,15 – 0,3
X 38 CrMo 16 1.2316 900 – 1.200 0,15 – 0,3
X 20 Cr 13 1.4021 1.000 – 1.200 0,15
X 30 Cr 13 1.4028 1.000 – 1.200 0,15
X 46 Cr 13 1.4034 1.000 – 1.200 0,15
X 46 Cr 13 1.4104 1.000 – 1.200 0,15
X 90 CrMoV 18 1.4112 900 – 1.100 0,15
X 90 CrMoV 18 1.4117 950 – 1.200 0,15
X 35 CrMo 17 1.4122 1.000 – 1.400 0,15
X 12 CrNi 18 8 1.4300 800 – 1.200 0,15
X 5 CrNi 18 10 1.4301 800 – 1.200 0,15
X 10 CrNiS 18 9 1.4305 800 – 1.000 0,15
X 5 CrNiMo 17 12 2 1.4401 800 – 1.200 0,15
X 2 CrNiMo 18 14 3 1.4435 800 – 1.200 0,15
X 5 CrNiMo 17 13 1.4449 800 – 1.200 0,15
X 5 CrNiMo 17 13 1.4535 1.000 – 1.200 0,15
X 6 CrNiMoTi 17 12 2 1.4571 800 – 1.200 0,15

Martensitaushärtbare Stähle

Material Material number Hardness HV 1 NHT in mm VS in µm
X 2 NiCrMo 18 8 5 1.6359 1.000 – 1.200 0,15 – 0,3 1 – 2

Hitzebeständige Stähle

Material Material number Hardness HV 1 NHT in mm
X 15 CrNiSi 25 20 1.4841 800 – 1.100 0,1
X 12 CrNi 25 21 1.4845 800 – 1.100 0,1

Grauguss

Material Material number Hardness HV 1 NHT in mm VS in µm
EN-GJL-150 / GG 15   300 – 450 0,2 – 0,4 4 – 10
EN-GJL-250 / GG 25   350 – 500 0,2 – 0,5 4 – 10
EN-GJS-400-15 / GGG 40 EN-JS 1040 400 – 600 0,2 – 0,5 4 – 10
GGG 42   400 – 600 0,2 – 0,5 4 – 10
EN-GJS-600-3 / GGG 60 EN-JS 1060 500 – 700 0,2 – 0,6 4 – 10
EN-GJS-700-2 / GGG 70 EN-JS 1070 500 – 700 0,2 – 0,6 4 – 10

Automatenstähle

Material Material number Hardness HV 1 NHT in mm VS in µm
9 S 20 1.0711 200 – 300 0,2 – 0,6 4 – 8
9 SMnPb 28 1.0718 200 – 350 0,2 – 0,6 4 – 8
10 S 20 1.0721 350 – 400 0,2 – 0,6 4 – 8
45 S 20 / 46 S 20 1.0727 350 – 450 0,2 – 0,6 4 – 8
44 SMn 28 1.0762 300 – 600 0,2 – 0,6 4 – 8

Sintermetalle

Material Hardness HV 1 NHT in mm VS in µm
Astaloy Mo 400 – 500 0,1 – 0,5  
Sint D30 350 – 500 0,1 – 0,5 5 – 20
Sint D35 150 – 300 0,1 – 0,3 5 – 20