Preparation And Tribological Properties Of ZrO₂-Al₂O₃ Composites Incorporated With BaCrO₄

In this paper,BaCrO₄ powders with different crystallographic morphologies and sizes were prepared by direct chemical precipitation methods or reverse micelle.The single-phase.Ba Cr₂O₄ powders with pure phase was prepared by solid reaction methods or co-precipitation method.ZrO₂-Al₂O₃/BaCrO₄ composites with different contents were prepared by ot pressing.The microstructure and tribological properties over a broad temperature range were investigated by XRD,SEM,Laser Raman spectroscopy and high temperatue friction and wear tester.Hereafter,the self-lubricating mechanisms of ZrO₂-Al₂O₃/BaCrO₄ ceramics were analysed.Using the first principle methods and the Castep modules in the Material Studio to calculate the bulk modulus and compression co-efficient of BaCrO₄,Ba Cr₂O₄ and Ba Cr O3 with different structures.The calculated results of bulk modulus for BaCrO₄,Ba Cr₂O₄ are respectively 28.1GPa and 71.6GPa.The crystallographic morphologies for BaCrO₄ are ball-like which was prepared by method of direct precipation using the EDTA as the addi tion,and the sizes are around 100 nm.The crystallographic morphologies for BaCrO₄ can not be adjusted by adjusting the concentration,but the particle’s size is reduced when the concentration is increased.Crystallographic morphologies and sizes of particles changes little in the aging time for 16 h,and are not affected by the ratio of cation and anion.The precursor of the BaCrO₄ without calcining are detected as carystalled by XRD analysis,so the sintering condition will be reinforeced once it get calcined.Crystallographic morphologies of BaCrO₄ is as flake with monodispersed.The pure-phased Ba Cr₂O₄ powders are successfully prepared by solid reaction method or co-precipitation method.The size of Ba Cr₂O₄ powders prepared by co-precipitation method is around 100 nm.The crystallographic morphologies of Ba Cr₂O₄ powders are spherical and well-dispersed.ZrO₂-Al₂O₃/BaCrO₄ composites with different contents were prepared by hot pressing.The lubratcationg properties of ZrO₂-Al₂O₃/BaCrO₄ composites in different condition including contents,temperatures and loads are compared and analysed.The lubricating properties of ZrO₂-Al₂O₃/BaCrO₄ composites reach the best only when the temperatues’ and contents’ ranges are properly designed.Composites with BaCrO₄ of 5wt.% contents in 400 oC own the best lubricating properties,whose friction coeffient and wear rate are respectively 0.32 and 4.25×10-5mm3/（Nm）.In room temperture,the lubricating mechanism of the composites is delamination wear.However in temperatures of 400 oC there are glazing layer and laye with small cells in the wearing surface,which impove the lubricating propeties.The main content of the glazing layer and wearing particle is Cr₂O₃.Both Glazing layer and layer with small cells jointly contribute to the high-temperature lubricating properties of ZrO₂-Al₂O₃/BaCrO₄ composites.