A MOSSBAUER-SPECTROSCOPY STUDY OF TI-FE INTERFACES PRODUCED BY THE PVD PROCESS

The deposition of hard coatings of the type TiC/N on steels enhances t he surface properties of the coated substrate. Steel substrates have b een pre-heated by the Are Bond Sputtering process (ABS(TM)), which use s a combined steered are and unbalanced magnetron arrangement. A criti cal stage of the ABS process is the titanium ion etch which improves t he adhesion of the TiN coating to the substrate. This work uses conver sion electron Mossbauer spectroscopy (GEMS) to study the phase formati ons in the near surface region of mild steel substrates after various Ti ion etch pre-treatments using the steered are discharge within the ABS process. The work has also investigated a second method using a Ba lzers BAI640R coating unit. Appropriate enrichment using the Mossbauer isotope Fe-57 has been used, enhancing the interfacial sensitivity of the GEMS technique to detect and identify phases formed by various io n etch processes. The results for the ABS pretreatments indicate that oxides and carbonitrides that may be formed during the initial stages of the Ti ion etch, are removed after a longer etch. For a conventiona l 10-min Ti ion pre-treatment a significant formation of both a crysta lline FeTi and a Te-rich amorphous phase occurs. The existence of the crystalline phase has also been confirmed by X-ray diffraction. For co mparison, samples that had been pretreated and coated in the Balzers p rocess show some evidence of the FeTi amorphous phase and the developm ent of an iron carbonitride, often identified as epsilon - Fe2-3(CN). (C) 1997 Elsevier Science S.A.