The effects of pre-implantation of steel substrates on the structural properties of TiN coatings

We have studied the effects of nitrogen pre-implantation of AISI C1045 steel substrates on the microstructure and microhardness of deposited TiN coatings. The substrates were implanted at 40 keV, to the fluences from 5 × 10¹⁶ to 5 × 10¹⁷ ions/cm², which was followed by deposition of 1.3-μm thick TiN coatings by reactive sputtering. Structural characterization of the samples was performed by standard and grazing incidence X-ray diffraction analysis, Rutherford backscattering spectroscopy and transmission electron microscopy. Microhardness was measured by the Vicker’s method. Nitrogen implantation up to 2 × 10¹⁷ ions/cm² induces the formation of Fe₂N phase in the near surface region of the substrates, which becomes more pronounced for higher fluences. Microstructure of the deposited TiN coatings shows a strong dependence on ion beam pre-treatment of the substrates. The layers grown on non-implanted substrates have a (200) TiN preferential orientation, and those grown on implanted substrates have (111) TiN preferential orientation. The change in preferred orientation of the layers is assigned to a developed surface topography of the substrates induced by ion implantation, and possible effects of distorted and altered crystalline structure at the surface. Ion implantation and deposition of TiN coatings induce an increase of microhardness of this low performance steel for more than eight times.