Defects Suppressing Method Of Al₂O₃-ZrO₂ Eutectic Ceramics Prepeared By Directed Laser Deposition

Melt growth Al₂O₃-ZrO₂ eutectic ceramic has excellent high temperature strength,creep resistance,oxidation resistance and ultra-high temperature microstructural stability,which is expected to become one of the ideal high temperature structural materials.Directed Laser Deposition?DLD?is a new technology for fabrication of melt growth eutectic ceramics,which can rapidly fabricate net-shaped ceramics.However,there are cracks and pore defects in samples,which limits the further development and application of the technology.Therefore,solving the problem of cracks and pores of fabricated structure is the key of fabricating the large-size,high-performance ceramics by DLD.Aiming at decrease the crack and pore defects in samples prepared by DLD,the methods of doping SiC particle?SiCp?with different particle size and proportion in eutectic matrix and optimizing process parameters were adopted.The complex structure of Al₂O₃-ZrO₂-SiC composite ceramics was formed,and the mechanical properties of the composite ceramics were tested.The main research contents are as follows:?1?The experiment of directed laser deposition was carried out,and doping SiC particles?SiCp?with different size and proportion into Al₂O₃-ZrO₂ eutectic matrix.The microstructure,the number and length of cracks and the porosity of samples were detected by Optical Microscope?OM?,Scanning Electron Microscope?SEM?and Hyper-Depth Microscopy?HDM?.X-ray diffractometer?XRD?and Electron Probe Microanalysis?EPMA?were used to detect the phase and elements composition.Through the detection and characterization of internal cracks,pores and microstructures,the reasons for the formation of them were analyzed,and the suppressing effect as well as the mechanisms of different particle size and proportion of SiCp on crack and pore defects were calculated and explained.?2?The optimal doping ratio and particle size of SiCp were determined by evaluating the effect of defect suppression.On this basis,optimization experiments of process parameters were carried out,and the influence of process parameters?laser power,scanning speed and z-axis lift?on the defects of Al₂O₃-ZrO₂-SiC composite ceramic samples were studied.Combined with the influence rules and actual preperaed process,suitable process parameters are selected to form parts with complex structure.Finally,the flexural strength,compressive strength and friction and wear properties of Al₂O₃-ZrO₂-SiC composite ceramics were tested.