 ION NITRIDING
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Steel
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Depth mm
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Temperature °C of ion nitriding
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Time (hours) of maintenance
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Hardness HV
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ST52 - C40
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0.1-0.8 mm
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480-500
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10-100
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550-600
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CAST IRONS (GS400)
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0.05 - 0.4 mm
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550
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10-60
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550-600
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34CrAlNi7 41CrAlMo7
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0.1-0.8 mm
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450-490
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30-150
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1000-1100
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38NCD4 -39NCD3
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0.1-0.8 mm
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480-500
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40-100
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600-650
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34NiCrMo8
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0.1-0.8 mm
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450-480
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70
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650-700
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18NCD5
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0.1-0.8 mm
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550
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20
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500-550
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Tab. 1 : Summary table of most important hardening and tempering steels and characteristics of ion process.
In Fig. 1 the comparative hardening curves are obtained from ion and gas nitriding on steel 34CrNiMo8, commonly used. The curves refer to high depth cycles to be used where specific or medium loads (i.e. Hertz load) are significant. Anyway the top hardness obtained with ion nitriding is always higher than the relative one obtained by the gas cycle.
Fig.1: Comparison between gas and ion nitriding for different depths on steel 34NiCrMo8. |
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| The reason for the light, regular and general increase of surface hardness in any kind of steel is due to the energy the plasma transmits in form of electric field to ion particles of nitrogen and hydrogen. When those hit the steel surface, they transform part of the energy into warmth. A part is used to further spread it into the surface, causing also a kind of superficial work hardening. |
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