Influences of SrSO₄ and Ag on High Temperature Tribological Properties of Spark-Plasma-Sintered ZrO₂(Y₂O₃)-Al₂O₃ Composites

Abstract

ZrO2(Y2O3)-Al2O3-SrSO4 nanocomposites incorporated with and without Ag addition have been fabricated by spark plasma sintering (SPS) to evaluate their friction and wear properties in sliding against alumina ball from room temperature to 600 oC. X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscopy were used to investigate microstructure and self-lubrication mechanisms of nanocomposites after wear tests at different temperatures. The ZrO2(Y2O3)-Al2O3-SrSO4 nanocomposite exhibits low and stable friction coefficients of 0.2 to 0.3 and wear rates in the order of 10-6 mm3/Nm at high temperatures. With the addition of Ag into the composite, the intermediate temperature lubricating property is greatly improved. Plastic deformation of SrSO4 and sliver during sliding plays an important role in formation of lubricating films on worn surfaces of nanocomposites. These lubricating films reduce the friction and wear of the ZrO2(Y2O3)-Al2O3 matrix composites.

Tribological Properties of Spark-Plasma-Sintered ZrO2(Y2O3)–Al2O3–Ba x Sr1−x SO4 (x = 0.25, 0.5, 0.75) Composites at Elevated Temperature

“…From the friction and wear data, the spark-plasma-sintered ZrO 2 (Y 2 O 3 )-Al 2 O 3 -Ba x Sr 1-x SO 4 (x = 0.25, 0.5, 0.75) composites show great potential for applications of self-lubricating sliding ceramic components at high temperature. With respect to some alkali-earth metallic sulfates, it is reported that BaSO 4 and SrSO 4 are easily softened, and form lubricating films on the worn surfaces to effectively reduce friction and wear at elevated temperature [8,12,[14][15][16]. As Ba x Sr 1-x SO 4 (x = 0.25, 0.5, 0.75) have the same barite-type crystal structure like BaSO 4 and SrSO 4 , it is inferred that they can also offer much promise as effective solid lubricants at high temperature.…”

“…In our previous work, the alkali-earth metallic sulfates with the same barite-type crystal structure as BaCrO 4 , such as BaSO 4 and SrSO 4 , possessed excellent lubricating ability, thermo-chemistry stability and innocuity. The spark-plasma-sintered ZrO 2 (Y 2 O 3 )-Al 2 O 3 matrix composite incorporated with silver and SrSO 4 showed optimum friction behavior with a friction coefficients of 0.2 to 0.3 and a wear rate in the order of 10 -6 mm 3 /Nm in a temperature range of room temperature to 600°C [12]. To date, only a limited amount of experiments have been performed on the available lubrication of ZrO 2 ceramics under both low and high temperature.…”

“…A series of self-lubricating ZrO 2 (Y 2 O 3 ) matrix composites based on these solid lubricants were developed by powder metallurgy or plasma spraying methods [8][9][10][11][12]. Selflubricating ZrO 2 (Y 2 O 3 ) matrix composites with MoS 2 synthesized by powder metallurgy provided very low friction and wear at low temperatures, however, a severe wear was found at 600°C or above because of the oxidation of MoS 2 [8].…”

“…Recently, the ternary compounds (ACrO 4 and ASO 4 , A = Ba and Sr) have been investigated as high-temperature solid lubricants for the ZrO 2 (Y 2 O 3 ) matrix composites [8,11,12]. The ZrO 2 (Y 2 O 3 ) matrix composite with 50 wt% BaCrO 4 synthesized by a powder metallurgy method presented low friction coefficient of 0.38 to 0.55 and a wear rate of 1.44 9 10 -5 to 5.35 9 10 -5 mm 3 /Nm from room temperature to 800°C.…”