X-ray photoelectron spectroscopy studies of hard coatings formed by titanium implantation on 304 stainless steel

Abstract

Titanium ions are implanted (at 30 keV) in 304 stainless steel to a dose of 1.8 × 10 17 ions cm −2 using 15 μA cm −2 and 5 μA cm −2 beam current densities for specimens 2 and 3 respectively. X-ray photoelectron spectroscopy (XPS) measurements are performed at different temperatures. The microhardness of implanted and unimplanted specimens is also measured. In specimen 2 the microhardness does not increase significantly and XPS measurements give evidence of carburized surface alloy formation. At 250°C TiO 2 is detected on the surface and it migrates into the bulk phase above 350°C. In specimen 3 the XPS measurements exhibit an absence of iron owing to the radiation-induced segregation of titanium on the surface. This specimen shows an increase in microhardness. The XPS measurements reveal a layer of (TiC x -C) on the surface which is suggested to be responsible for the increase in microhardness. Upon heating, TiC x is seen to move into the bulk phase and the carbon concentration is increased. These changes occuring at higher temperatures are suggested as having an effect on the wear-resistant properties of titanium-implanted 304 stainless steel.