Preparation And Tribological Properties Of Ceramic Matrix Composites Over Wide Temperature

Different particle size and morphology of SrSO₄ powder was prepared by chemical precipitation method in this paper. ZrO2?Y2O3.3mol%?-20 wt.%Al2O3?TZ3Y20A? which has the wear resistance, high temperature resistance and good mechanical properties was choosed as the matrix material. TZ3Y20A-SrSO₄ composites were then fabricated by spark plasma sintering methods, using SrSO₄ as the solid lubricant. The structure, morphologies and formation mechanisms of SrSO₄ powders and the effects of SrSO₄ solid lubricants on microstructure, mechanical properties and tribological properties were investigated by XRD, SEM, Raman, Vickers hardness tester and balance of density and high temperature friction.The crystal morphology of SrSO₄ powders could be controlled by the molar ratio?R? of [Sr²⁺]:[SO₄2-] in solution. With increasing R, the morphology of SrSO₄ powders varies from a needle- like to a plate- like feature, and the particle size changed from 250nm/100 nm to 350nm/300 nm. The main phase composition of TZ3Y20A-SrSO₄ were t-ZrO2, ?-Al2O3 and SrSO₄. With the addition of more SrSO₄ lubricantion phase, the Vickers hardness and the relative density of the composites increased.As test environment temperature from room temperature to 600?, the average friction coefficient and wear rate of TZ3Y20 A were increased. The numerical curve become more severe, and the width of fluctuation become biger. TZ3Y20 A at room temperature, the average friction coefficient and wear rate were 0.42, 9.2 10-6 mm3/N m, at 600 ?, the average friction coefficient of 0.91, the wear rate of 3.6 10-5 mm3/N m.With the increase of test temperature, the average friction coefficient and wear rate of the TZ3Y20A-50 wt.%SrSO₄ composite material which with needle- like SrSO₄ are decreased after the increase at 200?. The highest value is at 200?, and the lowest value under 600?. The average friction coefficient is 0.22, the wear rate of 0.03 10-5 mm3/N m. The average friction coefficient and wear rate of the TZ3Y20A-50 wt.%SrSO₄ composite material which with plate- like SrSO₄ have the same change trend. The highest value is at 200?, and the lowest value under 600 ?. The average friction coefficient under 600? is 0.26, the wear rate under 600? is 0.2 10-5 mm3/Nm. TZ3Y20A- SrSO₄ composite material has a better tribological properties than the matrix ceramic material. With SrSO₄ content increasing, the composites will have reduced friction coefficient and wear rate. The friction performance of composites were improved.Needle- like SrSO₄ is advantageous to the sintering densification, due to its smaller particle size compared with plate- like SrSO₄. So the composites with needle- like SrSO₄ powder has a higher density and vickers hardness. In the process of wear tests, composite material with needle-like SrSO₄ will form a more uniform, smooth, dense surface lubrication film. And it will reduce friction coefficient and wear rate, and it will show more excellent friction and wear performance. SrSO₄ has plastic deformation capacity, temperature rise test SrSO₄ plastic deformation ability stro nger, SrSO₄ enrichment in the wear surface. Under the effect of friction shear stress and compressive stress, the enriched SrSO₄ flat out on the wear surface, forming a layer of dense, uniform, smooth self lubricating film lubrication film in the process o f wear tests. It will improve the friction and wear properties of composite materials.