SYNTHESIS AND CORROSION PROPERTIES OF SILICON-NITRIDE FILMS BY ION-BEAM-ASSISTED DEPOSITION

Silicon nitride films SiNx were deposited on 316L austenitic stainless steel substrates by silicon evaporation and simultaneous nitrogen ion irradiation with an acceleration voltage of 2 kV. In order to study t he influence of the nitrogen content on changes in stoichiometry, stru cture, morphology, thermal oxidation behaviour and corrosion behaviour , the atom to ion transport ratio was systematically varied. The chang es of binding states and the stoichiometry were evaluated with XPS and AES analysis. A maximum nitrogen content was reached with a Si/N tran sport ratio lower than 2. The films are chemically inert when exposed to laboratory atmosphere up to a temperature of more than 1000 degrees C, XRD and SEM measurements show amorphous and featureless films for transport ratios Si/N from 1 up to 10, The variation of the corrosion behaviour of coated stainless steel substrates in sulphuric acid and h ydrochloric acid shows a minimum at medium transport ratios. This goes parallel with changes in porosity and adhesion. Additional investigat ions showed that titanium implantation as an intermediate step improve s the corrosion resistance considerably.