Tribological property enhancement of 3Y-TZP ceramic by the combined effect of CaF2 and MgO phases

Calcium fluoride (CaF2) often provides enhanced lubricating properties into ceramic composites when combined with other metal oxides to form some lubricating substrate. Present work unveils the superiority of small amount of CaF2 (1 wt%) as solid lubricant with the addition of metal oxide such as magnesium oxide (MgO) into 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) ceramic matrix. With addition of 0.5 wt% MgO in CaF2/3Y-TZP ceramic composite, the mean coefficient of friction (μ) was down to ∼42% and the subsequent wear rate (k) was reduced to ∼31% as compared to pure 3Y-TZP due to the presence of smooth tribo layer at the contacting interfaces. The tribological tests were performed against a hard-abrasive silicon carbide (SiC) counter surface under dry sliding condition. The wear mechanisms and elemental distributions in the worn surface were studied by field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray (EDS) setup. X-ray diffraction (XRD) analysis was carried out to identify different phases present in test specimens as well as in wear track. The presence of chemical states in the tribo layer was investigated by means of X-ray photoelectron spectroscopy (XPS) analysis.