Influence of Porosity on Friction and Wear of Tetragonal Zirconia Polycrystal

Abstract

Sliding wear properties of ultra-fine-grained (180 nm)very slow grain growth at 1150ЊC in a large range of dwell times. 9 (2) The stress-induced phase transformation from yttria-doped tetragonal zirconia (Y-TZP) ceramics were examined with porosities from 1.5% to 7%. On a pin-ontetragonal to monoclinic is almost completely suppressed by the ultra-fine grain size. 6,10 A tetragonal-to-monoclinic phase plate tribometer under dry-N 2 conditions, e.g., wear rates of the material increase by a factor of 5 by increasing porosity transformation has a significant effect on the tribological properties of TZP ceramics during sliding wear, 8,11 resulting in a with a factor of 5 (from 1.5 to 7.0 vol%). In all cases no (irreversible) phase transformation to monoclinic zirconia more complex wear process. took place during wear tests. The results for the relatively dense nanostructured materials showed significant evidence II. Experimental Procedure of plastic deformation and less microcrack formation. The morphology of the wear tracks in these ceramics indicate Nanocrystalline and weakly agglomerated zirconia powders (Y-TZP) are prepared by a gel-precipitation method using that the degree and amount of microcracks on the contact surface increased with porosity. A change in wear mechametal chlorides as precursor chemicals. More details about the preparation process have been reported elsewhere. 12 The nism is observed.specimens are uniaxially pressed in a die at 80 MPa to a rectangular form and subsequently isostatically pressed at 400 MPa. I. IntroductionThe ultra-fine-grained Y-TZP specimens with grain size 180 nm are densified at 1150ЊC for varying times by pressureless sin-P OLYCRYSTALLINE tetragonal zirconia (TZP) ceramics are tering or by sinter forging 13 to obtain 1.5%-7.0% porosities. promising in tribological applications due to their high Porosity was measured using the Archimedes technique in Hg flexural strength, hardness, and fracture toughness at room and grain size by SEM pictures using the linear intercept techtemperature or elevated temperature.1,2 The presence of porosity nique. 14 The surface of TZP specimens was subsequently generally has a negative influence on mechanical properties, polished with 0.05 m alumina powder. Subsequently the specsince pores can cause stress concentration, resulting in low imens were ultrasonically cleaned for 45 min in ethanol and strength.3 The presence of pores, distributed at grain boundthen annealed at 950ЊC for 10 min (heating and cooling rates aries, weakens the grain boundaries and leads to a reduction of 2ЊC/min) to remove the residual stresses produced by machinfracture energy. It is found that for TZP ceramics the variation ing and polishing. The pin materials used in all tests are comof fracture energy (␥), Young's modulus (E) and fracture toughmercially available sintered SiC spheres (diameter 4 mm) with ness (k IC ) with residual porosity follows an exponential relaa mirror-polished surface (Gimex Technische Keramiek B.V., tion. [4][5][6] It is expected that the...

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Structure and Tribological Performance of Nanostructured ZrO2-3 mol% Y2O3 Coatings Deposited by Air Plasma Spraying

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An investigation of different ceramic coating thermal properties

“…Latest works expose that microstructure and mechanical properties, such as grain size [12][13][14][15][16], porosity [17], hardness [18,19], fracture toughness [20], have strong effect on abrasive/sliding wear resistance of bulk ceramics and coatings under dry or lubrication circumstances. Among the reduction in the grain size of ceramics, their mechanical properties would be improved [21,22], which is helpful in improving the abrasive/sliding wear resistance of bulk ceramics and coatings [1,18,[12][13][14][15][16][17][18][19][23][24][25].…”