Effect of the composition profile and density of LPPS sprayed functionally graded coating on the thermal shock resistance

Abstract

Low Pressure Plasma Spraying (LPPS) is a promising coating method for Functionally Graded Material (FGM) expected to be able to reduce the thermal stress in high temperature environments such as a gas turbine. In this paper, we report the effect of the composition profile and coating density of LPPS sprayed FGM, consisting of ZrO 2-8 wt%Y 2 O 3 (YSZ) top coating, YSZ-Ni-20 wt%Cr (NiCr) FGM coating, NiCr under coating and copper substrate, on the thermal shock resistance evaluated by a modified temperature difference test. The density of YSZ and NiCr coating was successfully controlled by the chamber pressure and initial particle size in the range from 5.43 to 5.79 g/cm 3 and from 7.89 to 8.09 g/cm 3 , respectively. For an YSZ composition profile from NiCr under coating to YSZ top coating (in FGM), the highest thermal shock resistance was obtained when the fraction of YSZ increased with gentle slope just over NiCr coating and acute slope just under YSZ coating. Also, the higher density coatings tended to perform the higher thermal shock resistance. Initial cracks formed in the YSZ top coating propagated into YSZ parts in FGM coating through the grain boundary of YSZ and/or the interface between flattened NiCr and YSZ particles. After the cracks connected, the coupled cracks caused the coating spallation.

Influence of plasma jet temperature on the synthesis and structure of YSZ coatings

“…The higher density value of 5.20 g/cm 3 was determined for sample N7 deposited at 3350 • C. The density of coating was measured by Archimedes method, which excludes an open porosity effect [12]. In comparison, the density of 8YSZ obtained by low pressure plasma spraying is 5.43-5.79 g/cm 3 [13]. The density of the as-sintered 8YSZ coating produced by electrophoretic deposition, measured by the Archimedes method, is 72% [12].…”

Oxidation and Corrosion Resistance of NiCr-Re and NiCr-Re-Al2O3 Materials Fabricated by Spark Plasma Sintering

“…A promising alternative to metallic coatings is less expensive hybrid coatings based on oxides or carbides. Among commercially available materials recommended for combustion boiler protection, the following ones are often used: NiCr, NiCrTi, NiCrSi, NiCrMo, NiCrAl, NiCr-Cr 3 C 2 , special steels, and Inconel alloys [8][9][10][11][12][13][14]. The mentioned materials manifest good resistance to solid particle impingement erosion, high-temperature chlorine-sulfur corrosion, and thermal shocks.…”

Comparison of pure metal coating preparation by thermal spraying, cold spraying and electroplating methods

“…High-speed cold spraying is compressed air loading solid particle impact the substrate and forms dense coating. The supersonic gas jet is not absolutely cold, the gas temperature is between 500˚C and 600˚C so as to make the particles carry more energy and strengthen the adherence with the substrate [3][4][5] . In this study, copper coating on the high-voltage switch was deposited on aluminum alloy substrate by arc spraying, cold spraying and plating so as to make the switch more lightweight.…”