THE MICROSTRUCTURE OF SURFACE COATINGS APPLIED BY VARIOUS TECHNIQUES ON STEEL SUBSTRATES

I.Iordanova¹, K.S.Forcey², and M.Surtchev¹

¹ Dept. Solid State Physics, Sofia University, 5 Blvd. J.Bouchier, 1126 Sofia, BULGARIA
² Joint Research Centre, 21020 Ispra (VA) ITALY

Keywords: Thermally sprayed coatings, RFS and SIP surface coatings; qualitative X-ray phase analysis; stereometric metallography; ion beam techniques; SEM microprobe analysis.

Since the surface of a solid material is the location where interaction with the environment occurs, it is the region where properties such as wear and corrosion resistance are the most critical. Surface engineering is an economic way for the production of materials, tools and machine parts with the required parameters. Its techniques include all the methods (coating, implantation, sputtering, laser beam melting, etc.) by the means of which a modification of the surface could be achieved [1]. It could be expected that the properties of the surface will depend on its structure which is a function of both the material and the technological parameters of the applied surface treatment.

By the methods of X-ray diffraction, metallography, ion beam techniques and SEM microprobe analysis, an investigation into the microstructure of thermally sprayed, SIP and RFS coatings applied on steel substrates has been performed. Particular attention has been paid to the development and application of methods of stereometric metallography for the estimation of volume parameters of the spherical grains observed in the structure of the thermally sprayed coatings. The applied X-ray powder diffraction and ion beam methods (namely, RBS of a-particles and NRA employing the ¹⁶O(d,p)¹⁷O nuclear reaction) yielded phase information as well as revealing the chemical composition, thickness and macrostructure of the SIP and RFS coatings.

The results obtained reveal some new information on the mechanisms of structure formation and growth of the applied coatings. The investigation is expected to provide information for the optimization of the application techniques.

1. W.Giesler and H.A.Jehn (eds.), Advanced Techniques for Surface Engineering, Kluwer, Dordrecht, (1992).