Mechanical Properties of Yttria and Ceria Stabilized Zirconia Coatings Obtained by Suspension Plasma Spraying

International audiencePlasma generated by SG-100 torch was applied to spray suspension formulated with the use of ZrO2+8 wt% Y2O3 (8YSZ) and ZrO2+24 wt% CeO2+2.5 wt% Y2O3 (24CeYSZ) as solid phases. The solids have the mean size of about 8YSZ - 4.5 μm and 24CeYSZ - 3.9 μm and were obtained by milling of commercial powders Metco 204 NS and Metco 205NS respectively. The suspensions were formulated with the use of 20 wt. % of solid phase, 40 wt.% water, and 40 wt.% of ethanol. The plasma spray parameters were optimized by keeping constant: (i) the electric power of 40 kW; and, (ii) working gases composition 45 slpm of Ar and 5 slpm of H2. On the other hand, the spray distance was varying from 40 to 60 mm and torch linear speed was varying from 300 to 500 mm/s. The coatings were sprayed onto stainless steel substrates to reach the thickness ranging from 70 to 110 μm (8YSZ) and about 70 μm (24CeYSZ). The coatings microstructure was analyzed with the use of scanning electron microscope. Mechanical properties were tested with the use of indentation test and scratch test. The indentation test carried out with various loads ranging from 100 to 10000 mN enabled to determine elastic modulus and Martens microhardness. Young modulus of the coatings was in the range 71 to 107 GPa for 8YSZ and 68 to 130 GPa for 24CeYSZ coatings. Scratch test enabled to find the scratch macrohardness