Hot corrosion behavior of multi-layer suspension plasma sprayed Gd2Zr2O7/YSZ thermal barrier coatings

• This study investigates the corrosion resistance of double layer Gd2Zr2O7/YSZ, triple layer dense Gd2Zr2O7 / Gd2Zr2O7/YSZ and a reference single layer YSZ coating with a similar overall top coat thickness of 300-320 ÎŒm. All the coatings were manufactured by suspension plasma spraying (SPS), resulting in a columnar structure. Corrosion tests were conducted at 900°C for 8 hours using vanadium pentoxide and sodium sulphate as corrosive salts at a concentration of 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7 coatings exhibited lower corrosion resistance than the reference material, YSZ. Reaction between the corrosive salts and Gd2Zr2O7 results in the formation of gadolinium vanadate ( GdVO4) along the top surface and between the columns. While the stresses due to phase transformation of zirconia can be relieved to some extent by realigning of the columns in the top coat, it is believed that GdVO4 formation between the columns, along with low fracture toughness of Gd2Zr2O7 had resulted in lower corrosion resistance. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top, as a preventive layer for salt infiltration, did not improve the corrosion resistance.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Bearbetnings-, yt- och fogningsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Manufacturing, Surface and Joining Technology (hsv//eng)

Nyckelord

Atmospheric corrosion; Coatings; Corrosion; Corrosion resistance; Fracture toughness; Gadolinium; Plasma jets; Plasma spraying; Salts; Scanning electron microscopy; Sodium sulfate; Sprayed coatings; Sulfur compounds; Thermal barrier coatings; Thermal spraying; Vanadium; Vanadium compounds; Yttria stabilized zirconia; Zirconia; Zirconium compounds

Columnar structures; Corrosion tests; Gadolinium vanadates; Gadolinium zirconate; Hot corrosion; Reference material; Suspension plasma spraying; Vanadium pentoxide

Gadolinium compounds

Manufacturing and materials engineering

Produktions- och materialteknik

Production Technology

Produktionsteknik

Publikations- och innehållstyp

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