Influencia de las capas intermedias TixSi y TixSi / a-Si: H en la adherencia de recubrimientos de carbono tipo diamante

The effect of two different interlayers on the adherence of DLC coatings to AISI 316 L stainless steel was studied. Titanium‑silicon (TixSi) interlayers and titanium‑silicon plus amorphous hydrogenated silicon (TixSi/a-Si:H) interlayers were deposited. TixSi intermediate layers were grown with three different thicknesses via the RF sputtering technique, while a-Si:H interlayers and DLC coatings were deposited using a DC-PECVD system with an active screen as an additional cathode. The microstructural characterization of the titanium‑silicon interlayer was carried out through the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and chemical analysis was done by means of energy-dispersive X-ray spectroscopy (EDS), while DLC coatings were studied with Raman spectroscopy. The degree of adhesion of the DLC coatings to AISI 316 L stainless steel substrates was analyzed using critical load measurements and a VDI 3198 indentation test. XRD results showed that new crystalline phases were not present in the TixSi interlayer. XPS spectra showed a bond between the Sisingle bondFe and the Ti-Fe-O. The adherence results showed that the DLC coatings deposited using TixSi with 200 nm thickness exhibited a critical load value of 5 N, while the coatings with other thicknesses were completely delaminated when the same load was applied. These results suggested that the low adhesion of the DLC coating was due to the oxides formed at the TixSi-DLC interface. For the AISI 316 L/TixSi/a-Si:H/DLC coating, a critical load of 26 N was determined. The formation of titanium silicide, iron silicide, and silicon carbide in the interfaces allowed an increase in the adhesion strength between the interlayers. The Raman results showed that the DLC coatings exhibited good microstructural properties and hydrogen contents around 28 at.%. The DLC coatings also exhibited a hardness of 25 GPa.