Influences of substrate pretreatments and Ti/Cr interlayers on the adhesion and hardness of CrAlSiN and TiAlSiN films deposited on Al2O3 and ZrO2-8Y2O3 thermal barrier coatings
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Date
2019-02-20
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Abstract
Using atmospheric plasma spraying (APS), ceramic Al2O3 and ZrO2-8Y2O3 thermal barrier coatings (TBC) were applied on AISI H11 (1.2343) and subsequently polished to serve as a substrate to magnetron sputter CrAlSi7.5N and TiAlSi7.9N films. The influences of polishing as well as plasma etching processes on the surface roughness and residual stresses of the TBCs were correlated with the adhesion of the metal nitride films. As metallic interlayers are typically used to metallize insulating substrates to increase the film adhesion, the effect of different Cr and Ti interlayer thicknesses (50–150 nm) on the CrAlSi7.5N and TiAlSi7.9N adhesion was examined. Despite tensile stresses in the TBCs, a duplex coating structure, consisting of Al2O3 + Ti100 nm/TiAlSi7.9N, generated a high adhesion (Lc3 = 61.04 ± 2.36 N). In contrast to Cr, titanium interlayers are assumed to lead to a stress relaxation in the interface between the TBC and the PVD film. In general, using ZrO2-8Y2O3 as a substrate resulted in a minor adhesion of all PVD film combinations, which is traced back to lattice mismatches between the substrate and the films. Moreover, the number of pores on the TBC surface is crucial for the adhesion and hardness of CrAlSi7.5N and TiAlSi7.9N.
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Duplex coating, Thermal barrier coating, CrAlSiN, TiAlSiN, Coating adhesion, Microhardness