Wear behaviour of nanostructured and conventional 8 wt-%Y2O3-ZrO2 coatings against Si3N4 ball

The aim of the present paper is to investigate and compare the wear and tribological behaviour of two types of yttria-partially stabilised zirconia coatings, i.e. nanostructured and conventional zirconia. The coatings, 8 wt-% Y2O3-ZrO2, were produced using an air plasma spraying (APS) technique. Substrates used were made from AISI 304 stainless steel. To perform the wear tests, a pin on disc wear testing machine, using a 10 mm silicon nitride (Si3N4) ball as the pin, was employed. Coatings produced were characterised before and after being subjected to wear testing, using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray diffraction. Regarding the wear tests, effects of various parameters, such as wear distance, substrate temperature, disc rotating speed (sliding velocity) and applied normal load, were investigated. Results obtained (weight loss, wear rate, coefficient of friction and worn surface microstructure) revealed that under the wear conditions applied, the nanostructured zirconia coating exhibited a better wear resistance and tribological properties than the conventional one. Also it was observed that the difference in wear resistance between both coatings tested is a function of wear testing parameters such as wear distance, substrate temperature, disc rotating speed and applied normal load.