XPS and micro-mechanical characterisation of nitrogen ion implanted low alloy steel

The surface composition of low alloy steel after N-2(+) implantation was st udied with X-ray photo-electron spectroscopy (XPS). The effect of the impla ntation on the mechanical hardness was evaluated by ultra-micro hardness in dentation. Chemical characterisation of the surface indicated that a thin l ayer rich in N, C and SI was formed. It is shown that Fe played little role in the chemical composition and the structure of the modified surface. The mechanical hardness of N-2(+) implanted surface was 35-50 GPa compared wit h a value of 10 GPa for the untreated sample. It is thought that the high h ardness observed on the surface and in the sub-surface was as a result of c hemical modification to form a film of Sl doped carbon nitride. There is st rong evidence from the XPS and the nanoindentation studies that the bonding structure of the C-N in the near surface is essentially sp(3) types expect ed in crystalline C3N4. The value of nitrogen ion implantation as process f or improving the wear resistance of low alloy steels is emphasized.