Thermal shock behavior of thermal barrier coatings YSZ, YSZ/mullite and gradient coating YSZ/mullite on nickel base superalloy prepared by plasma spray (APS) method

Subject Areas :

Nader  Soltani ¹ (Department of Ceramic, Materials & Energy Research Center)
iman  mobasherpour ² (Department of Ceramic, Materials & Energy Research Center, Karaj, Alboorz, Iran)
Esmail  Salahi ³ (Department of Ceramic, Materials & Energy Research Center)
Ali  Sedaghat Ahangary ⁴ (Department of Ceramic, Materials & Energy Research Center)

Received: 2022-08-06 Accepted : 2022-10-10 Published : 2023-11-22

Keywords: plasma spray, YSZ, Mullite, Thermal barrier coatings, nickel-based super alloy,

Abstract :

In this research, thermal shock behavior, three types of yttria-stabilized zirconia (YSZ), yttria-stabilized zirconia and mullite coating (YSZ/Mullite) and gradient coating of yttria-stabilized zirconia and mullite (YSZ/Mullite) thermal barrier coatings on Inconel 738 low carbon nickel base superalloy along with bond coated by plasma spray method was compared.Using scanning electron microscopy (SEM) and X-ray diffraction (XRD), microstructure and phase analysis were done. The percentage of porosity and thermal shock of coatings at 1100°C temperature was investigated and compared. The results showed that with the increase of mullite in layer and gradient on YSZ coatings, the number of holes and porosity decreases, which is due to the increase in the amount of melted mullite particles. The percentage of porosity related to layer and gradient coating of mullite was obtained as 8 and 3.5% respectively. Using the results of the thermal shock test, it was determined that the lifetime of the mullite layer coating is longer than the mullite gradient coating and the YSZ coating. The maximum lifespan of the layered coating of mullite was recorded as 70 cycles of 10 minutes in a furnace with a temperature of 1100°C. The gradient coatings of mullite showed a higher percentage of shrinkage in thermal shock than the layered mullite coating.