High Temperature Behavior Of Cr₂AlC Ceramic And Its Composites

Cr2AlC ceramic is amore promising candidate for high temperature applications owing to its desirable thermal shock, oxidation and corrosion resistance at high temperature. The mechanism for abnormal thermal shock behavior of the Cr2AlC as one member of MAX phase has not been disclosed over10years. Its ultra-high temperature ablation behavior has not been reported up to now.The main research has been studied in the present work as follows:①Investigation of the abnormal thermal shock behavior of dense and coarse grain Cr2AlC bulks materials.②Synthesis and characterization of ZrC/Cr2AlC composites.③Study of the high temperature ablation behavior of Cr2AlC and ZrC/Cr2AlC composite.The main results are listed as follows:The main mechanism for abnormal thermal shock behavior of Cr2AlC in temperature range from800-1200℃is that the thermal shock induced cracks are instantly healed by the formation of reactants well adhering to the crack faces during quenching. And the Cr2AlC ceramic could withstand5cycles of thermal shock without catastrophic thermal failure.A dense ZrC/Cr2AlC composite was prepared by hot-pressing with ZrC and Cr2AlC powders with a molar ratio of0.18:1at1300℃with20MPa for1h in Ar atmosphere. Its flexural strength is～622MPa, much higher than400MPa of coarse grained Cr2AlC bulk.The linear ablation rate (LAR) of Cr2AlC under oxyacetylene flame increased from28.3μm/s for30s to44.2μm/s for60s. Its mass ablation rate (MAR) increased from0.33mg/s to13mg/s as ablation time increased from30to60s. In contrast, the LAR of ZrC/Cr2AlC composite increased greatly from31.7μm/s for30s to45.2μm/s for60s. Its MAR increased from-2mg/s to2.5mg/s as ablation time increased from30to60s.Microstucture and phase compositions were observed and analysed using X-ray diffracton and scanning electron microscope equipped with energy dispersive system.