PLASMA NITRIDING ON MATERIAL SURFACE

INTRODUCTION

Plasma nitriding or ion nitriding is a form of case hardening process in which utilizing plasma discharge physic to diffuse nitrogen into the surface of a ferrous alloy.


In this process, carbon together with nitrogen was introduced into the metal surface. The harden case, which is the nitriding layer is commonly known as ‘diffused case’ or ‘diffusion zone’.

ADVANTAGES OF CASE HARDENING

1. Less distortion compared to through hardening steel.
2. Fatigue properties of a part can be controlled and frequently improved.
3. Relatively inexpensive steel can be given wear-resisting properties which would be normally attained through the use of more highly alloyed and more expensive steels.
4. High surface hardness, improve resistance to wear and galling, improve fatigue life, improve corrosion resistance (stainless steel is an exception)

TYPES OF CASE HARDENING METHODS

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• Carburizing 
• Carbonitriding
• Nitriding (Gas nitriding, liquid nitriding, plasma nitriding)
• Nitrocarburizing
• Boriding

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• Sulfurizing
• Sulfonitrocarburizing
• Oxidation
• Induction (Flame, magnetic, shell, electron-beam, laser)
• Plating and Sprayed metal coating

PROCESS PARAMETERS

• Temperature (400-600°C) and Pressure (0.5-7 mbars)
• Gas composition (Ammonia, Nitrogen, Methane Hydrogen and Argon).
• Time (4 - 30 hrs depending on case depth).
• Voltage and Current intensity
• Pulse duration, Pulse pause frequency and Pulse pause duration

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Plasma nitriding is achieved using a D.C glow discharge technology. It utilizes a Direct Current electricity source to break up nitrogen gas (N2) into nitrogen ion (N+). This nitrogen ion is then absorbed by the metal surface to harden it.
There are three types of nitriding layer that could be formed during plasma nitriding treatment.

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SUITABLE MATERIAL FOR PLASMA NITRIDING

LOW AFFINITY STEEL + NITROGEN
1. Carbon steel
2. Low alloy steel
HIGH AFFINITY STEEL + NITROGEN
1. Medium alloy steel
2. Tool steel
3. High speed steel
4. Stainless steel

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