CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

Chapter 5
The unimplanted specimen (Fig. 5.4a) revealed austenite microstructure in oxalic acid
medium. However, the presence of martensite phase, and any abnormal ferrite phase present could
not be confirmed by etching with Vilella’s reagent, and Murakami’s reagent (Fig. 5.4b-c). The
reason is dissolution of superficial layer of martensite, and ferrite layer in the as polished
specimens during etching. As in the case of unimplanted specimen, no ferrite microstructure was
observed, for implanted specimens also it was not observed. The martensite phase at lower dose of
1×10 16 N + /cm 2 could not be revealed metallographically because of unknown depth, and extent of
martensite formation (Fig. 5.4d). Second important factor is that the extent of martensite formation
is dependent on energy of implantation, dose rate, and type of ion implanted. The degree of
martensite transformation is higher for heavier ions. Study carried out by Chayahara et al [161] to
investigate martensite transformation on 304 SS by high energy (1.5 MeV) implantation of heavier
ions (Au + ) using TEM has revealed fewer martensite grains. However, in the present study as the
energy of implantation and mass of ion implanted are small, the martensite layer formed is very
thin to reveal the microstructure metallographically. As the dose rate increases the martensite layer
formation is also coupled with nitride formation [162], and this has been reflected by the
disappearance of main as well as additional martensite peaks at 44.7º, 65°, and 82.3° at dose of
1×10 17 N + /cm 2 , 2.5×10 17 N + /cm 2 , respectively. The martensite area provides defects and nitride
nucleation sites, and acts as sinks for nitrogen [162]. Thus, at higher doses the martensite
microstructure could not be revealed metallographically [21].
5.2. 5 X-ray photoelectron spectroscopy study
The detailed analysis of the Cr2p 3/2 and N1s energy levels has been carried out by
deconvoluting the high resolution regions by asymmetric peak fitting procedure. The data
presented in Fig. 5.5a-b is from the dose of 1×10 17 N + /cm 2 after sputtering for 3 min corresponding
to erosion of 6 nm from the surface. The binding energy shift of Cr-Cr bond corresponding to the