Surface hardening by means of plasma immersion ion implantation and nitriding in glow discharge with electrostatic confinement of electrons

Sergey N Grigoriev,Yury A Melnik,Alexander S Metel,Marina A Volosova,S.N Grigoriev,M.A Volosova

doi:10.1051/meca/2015093

Abstract

At argon or nitrogen pressure 0.005–5 Pa a metal substrate is immersed in plasma of glow discharge filling a vacuum chamber and negatively biased to U = 1−10 kV. Emitted by substrate secondary electrons bombard the chamber walls and it results in growth of electron emission chamber walls and rise of gas ionization intensity inside chamber. At pressure p< 0.05 Pa nonuniformity of plasma density does not exceed ~10%. Measurement results of sheath width d between homogeneous plasma and a lengthy flat substrate were used to calculate dependence of the ion current density ji on its surface and ion-electron emission coefficient γi. The dependence allows evaluation of average dose of ion implantation on any complex-shaped product of the same material.

Highlights

Plasma immersion ion implantation (PIII) is nowadays widely used in industry for surface strengthening of various machine parts
Depth of ion penetration is directly proportional to energy of ions, and for this reason width of modified layer reaches maximal at applied voltage value only if ions pass through positive space charge sheath between plasma and product surface without collisions with gas molecules
In order to treat any product it is needed to fill with homogeneous plasma a chamber with sizes exceeding the sum of product width and doubled sheath width

Summary

Introduction

Plasma immersion ion implantation (PIII) is nowadays widely used in industry for surface strengthening of various machine parts. Essence of this method consists in immersion of product to be treated in plasma and application to this product of negative high-voltage pulses, which extract from plasma and accelerate ions [1, 2]. Width of surface layer modified through ion implantation is determined by depth of penetration into material of ions bombarding its surface. Depth of ion penetration is directly proportional to energy of ions, and for this reason width of modified layer reaches maximal at applied voltage value only if ions pass through positive space charge sheath between plasma and product surface without collisions with gas molecules. Despite sophisticated methods of plasma production, expensive microwave power supplies and other equipment used to fill vacuum chamber with homogeneous plasma, working nitrogen pressure in vacuum chambers of known facilities

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Conclusion