Preparation Of Surface Texture And Its Enhancement On Tribological Properties Of ZTA Ceramic

Nowadays,increasing people suffer from joint diseases due to the aging problem and frequent traffic accidents.Compared with drug therapy,joint replacement surgery has been considered as an effective way to treat joint diseases.Therefore,artificial joints materials with excellent properties have attracted more and more attentions from researchers.Ceramic materials,such as Zr O₂ and Al₂O₃,are recognized as potential materials due to its high strength,excellent chemical stability and corrosion resistance.But tribological properties of ceramic materials have been restricted by the ceramic brittleness.This paper aims to produce surface texture on the ceramic surface for improving the tribological performance of ceramic materials and extend its application in the field of artificial joints.In this paper,25 wt.%ZrO₂（3 mol.%Y₂O₃）toughened Al₂O₃（ZTA）ceramic with excellent mechanical properties were prepared by hot-pressed sintering method.Meanwhile,the microstructure,mechanical properties and tribological performanceof ZTA ceramic were studied.Surface texture with well-defined circular dimple array on ZTA ceramic surface was produced by a fiber laser.The effects of laser power,Q-switched frequency,engraving speed,and pulse width on the size and the quality of circular dimple were explored.The obtained optimum process parameters of laser power,Q-switched frequency,engraving speed and pulse width were 12 W,50 kHz,1000 mm/s and 45 ns,respectively.Correspondingly,the diameter of circular dimple was about 95μm,the depth of circular dimple was about 20μm,the thickness of heat-affected zone was 13.5μm,roundness was 0.88 and taper was 0.6.Finally,the texture with area densities of 6%,12%,32%,and 45%were built successfully on ZTA ceramic surface under the optimum process parameters.The tribological performance of ZTA ceramic were investigated under dry sliding condition against Al₂O₃ pin,and the effect of textured area density（0%,6%,12%and32%）on tribological properties was also determined.Under a load of 40 N,the friction coefficients and wear rates of ZTA ceramics increased wtih textured area density increasing from 0%to 32%.The friction coefficient increased from 0.48 to 0.63,and the wear rate increased from 7.8×10^-9mm³/Nm to 1.2×10^-8mm³/Nm.It was concluded that surface texture made no difference to improve tribological properties of ZTA ceramic.However,the friction coefficients and wear rates of the ZTA ceramic first decreased,then increased wtih textured area density increasing from 0%to 32%under the load of70 N and 100 N.When textured area density increased to 12%,the friction coefficient and wear rate were decreased from 0.73 and 9.2×10^-4mm³/Nm to the minimum values of 0.49 and 4.9×10^-5mm³/Nm under a load of 70 N,respectively.Meanwhile,under a load of 100 N,the ZTA ceramic with no surface texture had a friction coefficient of 0.50 and a wear rate of 3.75×10^-7mm³/Nm.With textured area density increasing to 6%,the friction coefficient and wear rate were decreased to the minimum values of 0.47 and8.5×10^-8mm³/Nm,respectively.When the load were 70 N and 100 N,the surface texture play a critical role in the improvement of tribological properties of ZTA ceramic,which was ascribed to the trapping of the wear debris and reduction of the plough wear.Under simulated fluid lubricated condition,tribological tests were performed against Al₂O₃ pin for ZTA ceramic with textured area density of 0%,6%,12%,32%and45%.With a load of 40 N,the friction coefficients of ZTA ceramic decreased from0.202 to 0.165 with textured area density increasing from 0%to 45%.When the load increased to 70 N and 100 N,the friction coefficient first increased and then decreased with the increase of textured area density.Friction coefficients of untextured ZTA ceramic were 0.186 and 0.192 under the load of 70 N and 100 N.When textured area density got to 45%,the friction coefficients decreased to the minimum values of 0.175 and 0.178.Under lubricated condition,the surface texture will collect the lubrication and provide carrying capacity during the friction process,which results in improvement of ZTA ceramic tribological behaviors.