Failure mechanisms of interfacial coatings (MCrAlY+8YSZ) on high temperature solid particle erosion

In order to study the influence of the bond coat on the erosion resistance of the thermal barrier coating (TBC), two different bond coats (NiCrAlY and NiCoCrAY) were deposited onto Inconel 718 substrate by using Atmospheric Plasma Spray (APS). After that topcoat Yttria Stabilized Zirconia with the Y₂O₃ content of 8 weight % (8YSZ) coatings were deposited by APS method onto the bond coats also. Alternative test rig compliant with the ASTM G211-14, was used in experiments. These experiments were performed at three different air temperatures (21°C, 300°C and 600°C), three different erosive particle impact angles (30°, 60° and 90°), constant particle impact velocity (~97 m/s) and particle size (400 µm Al₂O₃) after which, the erosion rate-impact angles results were obtained. Scanning electron microscopy (SEM) images, X-ray diffraction (XRD) analysis, Energy dispersive X-ray (EDX) mapping and EDX elemental analysis were conducted to assess the effectiveness of bond coating and ceramic topcoats to reduce wear at high temperatures. The importance of adhesion at the interface between bond coatings and ceramic topcoats was determined. However, erosion resistance generally increased with temperature, and this resistance effect tended to decrease with the presence of Cobalt.