Abstract No.:
2895

 Title:
Thermo-mechanical and hot corrosion testing of selected HP/HVOF sprayed coatings for power industry applications

 Authors:
Frantisek Zahalka / Research and Testing Institute Pilsen s.r.o., Department of Thermal Spraying, Czech republic
Michaela Kasparova / SKODA VYZKUM s.r.o, Czech republic
Sarka Houdkova/ SKODA VYZKUM s.r.o, Czech republic

 Abstract:
Stellite 6, CoNiCrAlY, Hastelloy 276, Tribaloy 400, Inconel 718, WC-CrC-Ni and CrC-CoNiCrAlY powders were thermally sprayed using the high velocity oxygen fuel (HP/HVOF) method with JP-5000 gun onto substrates made from P91 and 15 128 steel. For evaluation of the thermo-mechanical properties a SMITWELD TTU 2002 apparatus was used. The temperature changed linearly without pauses during testing within the limits of 200 and 660 °C at the rate of 15°C/s. One temperature cycle took 1 minute and for each material 50 temperature cycles were applied. All samples were exposed to corrosion conditions in enclave at 550°C, at pressure 245 bar for 150 hours. Feed water was demiwater with dissolved oxygen which was in balance with atmosphere (8 ppm). The conductivity of the feed water was less than 2 mS/cm. Additional testing as microhardness, microstructure and surface evaluation, abrasion wear test, chemical and phase composition were evaluated. Evaluation based on SEM observation of the microstructure and changes of the mechanical properties of the coatings materials after the tests was used to identify material degradation, presence of the cracks or another significant changes in coating microstructure. The results shows a dependence of the cracks presence in coating on substrate material for used experimental condition, although for some coatings superior corrosion and crack resistance independent on substrate material was observed.

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