Process And Mechanism Of Laser Engineered Net Shaping Thin-walled Al₂O₃-YAG Ceramic

ceramic materials have excellent mechanical properties, such as high strength, good wear resistance, excellent corrosion resistance and high temperature resistance etc. In particular. YAG adding to Al2O3 which is called Al2O3-YAG composite ceramic can not only increase the toughness of pure Al2O3 ceramics but also improve the high temperature creep. Therefore, the Al2O3-YAG composite ceramic can be applied to the important parts in extreme environments such as high temperature oxidation. Laser Engineered Net Shaping (LENSTM) is one of laser rapid prototyping technologies developed by multi-layer cladding technology. LENSTM can directly form three-dimensional parts by melting the powder material using laser beam, which has advantages as short manufacturing cycle, high material utilization, good mechanical properties of products and flexible Manufacturing. The technology used in produced ceramic can rapidly manufacture complex structure parts without mould, which is very difficult for traditional methods. So this technology is very significative to promote ceramic material application in high-end equipment.In this paper, Al2O3-YAG composite ceramic thin-walled parts were produced by LENSTM using Al2O3 and Y2O3 powder. The influence of laser power and substrate preheating on the shape, cracks and microstructure of the samples were studied by the method of experiment and ANSYS finite element simulation. Besides, this paper has also analyzed the phase composition, microstructure characteristics, hardness and fracture toughness of the samples by X-ray Diffraction, Scanning Electron Microscope, Electron Probe and D Type Hardness Tester. The main content of this study are as follows:(1) A finite element model of the thin-walled samples was established according to the actual process and its reliability was verified through the temperature measurement of a point.(2) Al2O3-YAG composite ceramic thin-walled parts were produced by LENSTM using Al2O3 and Y2O3 powder. The influence and mechanism of laser power on the shape and crack of the thin-walled samples was researched. Substrate preheating was used to restrain the crack. The influence and mechanism of substrate preheating on shape and crack of the samples was studied by experiment and temperature simulation.(3) The phase composition of the samples was tested by X-ray Diffraction and Electron Probe. Microstructure of the samples was observed by Scanning Electron Microscope, the microstructure characteristics of the samples are analyzed under the condition of different laser power and substrate preheating method. The analysis of organization characteristics on different height of the sample was made. Al2O3-YAG composite ceramic with uniform eutectic organization was produced by adjusting the materials proportion.(4) The density of the samples was calculated by measuring regular sample pieces. The hardness and estimating fracture toughness was test by the D Type Hardness Tester on different height of the sample. The basic mechanics performance evaluation of Al2O3-YAG ceramic produced by LENSTM was given.