CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

Chapter 5
C H A P T E R 5
The effects sub-surface modification using nitrogen ion implantation, and its effect on the
corrosion resistance of AISI 304L stainless steel in 1 M HNO 3 medium is investigated. Nitrogen
ion was implanted at 70 keV in the dose range of 1×10 15 , 1×10 16 , 1×10 17 and 2.5×10 17 N + /cm 2 ,
respectively. Glancing Incidence X-ray Diffraction results for unimplanted, and up to dose of
1×10 16 N + /cm 2 showed co-existence of -Fe & -Fe, and at higher doses (1×10 17 , 2.5×10 17
N + /cm 2 ) preferential formation of chromium nitride was observed. X-ray photoelectron
spectroscopy investigation confirmed the formation of chromium nitride at higher doses.
Electrochemical corrosion investigation revealed nobler open circuit potential, decrease in
passive current densities and corrosion current densities, and increase in polarization resistance
with increase in dose rate. Surface morphology analysis after polarization study using atomic
force microscope showed grain boundary dissolution for unimplanted specimens, and resistance
to surface dissolution with increase in dose rate for implanted specimens.
5.1 Introduction
Sub-surface modification is one of the technologically important methods to independently
optimize the properties of near-surface of metallic materials, leaving underlying bulk unaffected
for improved tribological properties, introduction of desired chemical properties, and to alter the
metallurgical properties at nano-scale [132-136]. It is largely carried out by alloying with suitable