Zhou Kesong

Properties of Thermal Barrier Coatings Made of Different Shapes of ZrO2-7wt%Y2O3 Powders

Abstract Atmospheric plasma sprayed ZrO2-7wt%Y2O3 (7YSZ), functioned as thermal barrier coatings (TBCs), are widely used in industrial gas turbine engines so as to protect the superalloy blades from failure. Using NiCoCrAlYTa powder as starting material a bond coating was prepared on K4169 superalloy substrate by high velocity oxygen flame (HVOF). Ceramic top coatings were prepared on the above mentioned bond coating by atmospheric plasma spray (APS) using agglomerated and sintered (referred to as “AS”) powder and hollow spherical (referred to as “HS”) powder, separately as starting materials. The microstructures of above two sorts of thermal barrier coatings (TBCs) were characterized by scanning electron microscope (SEM) and industrial computed tomography (ICT). Thermal oxidation resistance, thermal shock and adhesion strength, insulation property of both TBCs were compared. The results indicate that the TBCs made of HS have more pores and microcracks than the TBCs made of AS. Different porosities of TBCs have no obvious effect on thermal oxidation property. The TBCs made of HS have better thermal shock resistance and insulation property than the TBCs made of AS, but the formers adhesion strength is lower than the laters. The former is 35 MPa, while the later is 54 MPa.

Tribological Behavior of HVOF Cermet Coatings as Alternative to Cr-Plating in Artificial Salt-Fog Atmosphere

Abstract Two kinds of cermet coatings (WC-10Co4Cr and Cr3C2-NiCr) were prepared by high velocity oxygen fuel (HVOF) to enhance the wear- and corrosion-resistance of key components in aviation and marine fields. Their tribology behavior in salt-fog condition were studied by a reconstructive friction testing machine equipped with artificial salt-fog spraying apparatus. Traditional chrome plating (Cr-plating) was also researched for comparison. The results show that different coating display different wear-mechanisms. Cr-plating exhibits mainly adhesive-wear mechanism, however, the WC-10Co4Cr coatings displays mainly abrasive-wear mechanism, while the Cr3C2-NiCr coating shows both mechanisms of adhesive-wear and abrasive-wear. Salt-fog atmosphere has important effects on tribological behavior of the coatings, which reduces the friction coefficient and corrosion loss of the coatings, resulting in the wear-mechanism of WC-10Co4Cr coating change to oxidation/corrosion wear.