Improvement of Thermal Cycling Resistance of AlxSi1−xN Coatings on Cu Substrates by Optimizing Al/Si Ratio

Abstract

The effect of the elemental composition of AlxSi1−xN coatings deposited on Cu substrates by magnetron sputtering on their structure, mechanical properties and thermal cycling performance is studied. The coatings with Al-Si-N solid solution, two-phase (AlxSi1−xN nanocrystallites embedded in the SixNy tissue phase) and amorphous structure were obtained by varying Al/Si ratio. It is shown that polycrystalline coatings with a low Si content (Al0.88Si0.12N) are characterized by the highest thermal cycling resistance. While the coatings with a high and intermediate Si content (Al0.11Si0.89N and Al0.74Si0.26N) were subjected to cracking and spallation after the first cycle of annealing at a temperature of 1000 °C, delamination of the Al0.88Si0.12N coating was observed after 25 annealing cycles. The Al0.88Si0.12N coating also exhibited the best barrier performance against copper diffusion from the substrate. The effect of thermal stresses on the diffusion barrier performance of the coatings against copper diffusion is discussed.

Effect of La2O3 on Microstructure and Thermal Conductivity of La2O3-Doped YSZ Coatings

“…TBCs, having lower thermal conductivity, are widely used in turbine blades, which are usually operated at very high temperatures [4,5,6,7]. Engines operating at high temperatures require materials with lower thermal conductivity in order to insulate the other parts of the engine from hot burning gases [8,9,10,11,12]. In addition to the Y 2 O 3 -ZrO 2 (YSZ) TBCs, it has been found that lanthanum-doping can effectively reduce the thermal conductivity of YSZ TBCs.…”