No abstract

Three mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) with 0.5 wt% of magnesium oxide (MgO) and 6 wt% of molybdenum (Mo) were prepared by the pressureless sintering process, and the friction and wear behavior of the ceramic composite were studied against the alumina disc. Tribological tests were carried out both at room temperature as well as at an elevated temperature (500 °C). The result revealed that a substantial reduction of ∼50% in the friction coefficient and ∼31% reduction in the wear rate were achieved while 6 wt% Mo was added into the 3Y-TZP matrix operational at 500 °C. No significant tribological influence was observed with the addition of Mo at the normal operating temperature. The minimum coefficient of friction and low specific wear rate were achieved because of the formation of MoO3 in between the mating surfaces at elevated temperature. The worn surfaces were characterized by means of field emission scanning electron microscopy (FESEM). The formation of MoO3 phases was identified by wear debris analysis which was performed with the help of X-ray photoelectron spectroscopy (XPS).

No abstract

An innovative approach was adopted for fabricating ZTA–MoS2 self-lubricating ceramic composite with inclusion of hydrothermally synthesized nano MoS2 through the pores of perforated ZTA ceramics. This method avoided the exposure of MoS2 in high temperature environment due to its in-sensitiveness during traditional sintering techniques. Different weight percentages (wt.%: 0, 5, 10 and 15) of graphite were incorporated to produce porous ZTA ceramic by means of cold press sintering followed by insertion of nano MoS2 into the matrix. Best tribological characteristics was obtained with 10 wt% graphite-ZTA-MoS2 specimen which offered an improvement of ~66% in coefficient of friction and ~96% in specific wear rate when dry sliding tests were carried out against Si3N4 in high vacuum(5.0×10−4 mbar). Nano MoS2 was sheared off at the contacting interface during sliding under load to provide tribological enhancement of the composite. Delamination was found as the dominating wear mechanism in ZTA-MoS2 composite during wear test.

The aim of the study was to investigate the friction and wear phenomena of 3 mol % yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) ceramics with the inclusion of copper oxide (CuO) in large area conformal contact geometry. The pin-on-disk tribometer was used to conduct the dry sliding test using CuO/3Y-TZP as pin and alumina as counter surface. The coefficient of friction (μ) for CuO-added 3Y-TZP was decreased by ∼38% compared to pure 3Y-TZP due to formation of protective tribo film to the substrate. In addition, the experiments also showed that the specific wear rate (k) was reduced by ∼54% with the inclusion of CuO in to 3Y-TZP matrix. The different phases of the zirconia, copper, and yttria as well as the phase transformation before and after sliding test were identified by X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDS) analysis revealed the existence of CuO in the patchy layers in the worn-out surface of the tested CuO/3Y-TZP sample leading to lower coefficient of friction and improve the wear resistance against alumina counterface in conformal contact geometry. Severe wear mechanism was the dominating factor due to the local plastic deformation of the large number of asperities since the pair of contact was conformal.