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2022
Book Article
Title
Oxidation resistance of PECVD Ti-Si-C-N nanocomposite coatings
Abstract
Introduction:
Nanocomposite coatings received increasing attention in recent years due to outstanding mechanical and thermal properties primarily provided by their nanostructure [MOR20], [PIL08], [THA13]. The nanocomposite structure, consisting of an amorphous (a-) matrix enveloping nanocrystalline (nc-) grains, offers advanced mechanical properties, e.g. high hardness. The oxidation resistance of Ti-Si-C-N coatings is investigated in this study. Tribological tests by Ma et al. [MA07] showed lower coefficients of friction for Ti-Si-C-N compared to Ti-Si-N at room temperature as well as at 550 °C.
Method:
Ti-Si-C-N coatings were deposited on mirror finished (polished) DIN 1.2343 hot working steel and single-crystalline Si-wafers via Plasma Enhanced Chemical Vapor Deposition (PECVD). TiCl4, Si(CH3)4, CH4, and N2 were used as precursor gases with addition of H2 for reduction of TiCl4 and Ar to support the glow discharge during coating deposition. The chemical composition was determined via Electron Probe Microanalysis (EPMA). X-ray diffraction (XRD) measurements were performed at Beamline BL9 [KRY06] of the synchrotron light source DELTA (TU Dortmund, Dortmund, Germany). In order to determine the lattice orientation with respect to the samples surface, a MAR345 image plate detector was used. The energy of the incident photon beam was E0 = 27 keV and the beam size was set to 1.0 x 0.7 mm2 (h x v). The angle of incidence was 1°. These experiments were carried out at room temperature and elevated temperatures of 750 °C, 775 °C, and 800 °C. Raman spectroscopy was performed on samples tempered in air for 30 min at 850 °C to identify amorphous phases in the nanocomposite, because XRD won’t yield this information.
Results and discussion:
EPMA measurements revealed a chemical composition of 30.9 at.-% Ti, 10.5 at.-% Si, 41.0 at.-% C, and 14.8 at.-% N with additional 1.3 at.-% O and 1.6 at.-% Cl as residual elements from the deposition process. The XRD experiments yield information on lattice structure and phase configuration. Figure 1 shows the two-dimensional diffraction images of a Ti-Si-C-N layer in the as-deposited state. A distinct texture in the scattering intensity of the layer indicating an orientation of the (00l) planes of the cubic layer structure parallel to the substrate surface is observed.
Nanocomposite coatings received increasing attention in recent years due to outstanding mechanical and thermal properties primarily provided by their nanostructure [MOR20], [PIL08], [THA13]. The nanocomposite structure, consisting of an amorphous (a-) matrix enveloping nanocrystalline (nc-) grains, offers advanced mechanical properties, e.g. high hardness. The oxidation resistance of Ti-Si-C-N coatings is investigated in this study. Tribological tests by Ma et al. [MA07] showed lower coefficients of friction for Ti-Si-C-N compared to Ti-Si-N at room temperature as well as at 550 °C.
Method:
Ti-Si-C-N coatings were deposited on mirror finished (polished) DIN 1.2343 hot working steel and single-crystalline Si-wafers via Plasma Enhanced Chemical Vapor Deposition (PECVD). TiCl4, Si(CH3)4, CH4, and N2 were used as precursor gases with addition of H2 for reduction of TiCl4 and Ar to support the glow discharge during coating deposition. The chemical composition was determined via Electron Probe Microanalysis (EPMA). X-ray diffraction (XRD) measurements were performed at Beamline BL9 [KRY06] of the synchrotron light source DELTA (TU Dortmund, Dortmund, Germany). In order to determine the lattice orientation with respect to the samples surface, a MAR345 image plate detector was used. The energy of the incident photon beam was E0 = 27 keV and the beam size was set to 1.0 x 0.7 mm2 (h x v). The angle of incidence was 1°. These experiments were carried out at room temperature and elevated temperatures of 750 °C, 775 °C, and 800 °C. Raman spectroscopy was performed on samples tempered in air for 30 min at 850 °C to identify amorphous phases in the nanocomposite, because XRD won’t yield this information.
Results and discussion:
EPMA measurements revealed a chemical composition of 30.9 at.-% Ti, 10.5 at.-% Si, 41.0 at.-% C, and 14.8 at.-% N with additional 1.3 at.-% O and 1.6 at.-% Cl as residual elements from the deposition process. The XRD experiments yield information on lattice structure and phase configuration. Figure 1 shows the two-dimensional diffraction images of a Ti-Si-C-N layer in the as-deposited state. A distinct texture in the scattering intensity of the layer indicating an orientation of the (00l) planes of the cubic layer structure parallel to the substrate surface is observed.
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