The friction and wear characteristics of plasma-sprayed ZrO2-Cr2O3-CaF2 from room temperature to 800°C

The friction and wear characteristics of low-pressure plasma-sprayed (LPPS) ZrO2-Cr2O3-CaF2 from room temperature to 800°C were studied by using a high-temperature reciprocating wear tester. At room temperature, friction of ZrO2-Cr2O3-CaF2 composite coating against Al2O3 sphere was quite high, and exhibited a decrease trend with the increase of load from 30 N to 80 N. At 700°C, the composite exhibited the lowest friction and wear among all selected temperature conditions. Brittle fracture and delamination with large wear sheets were considered as the dominant wear mechanism at room temperature. At 400°C, microfracture dropping become more dominated. However, plastic deformation, formation of CaF2 lubrication films and particle removal of Cr2O3 appeared as the main wear mechanisms at elevated temperatures. CaF2 acting as an effective lubricant at 600°C and 700°C reduced the friction and wear of the composite. Cr2O3 particles played a very important role on controlling the size and type of microcracks and preventing or deflecting the microcrack propagation during 700°C test. Cr2O3 particles also acted as hard barriers to resist the scratching and high-temperature deformation of ZrO2-CaF2 matrix without increasing the friction. To a great extent, wear mainly depended on the degree of debonding and removal of Cr2O3 particles at 700°C.