Different Color Al₂O₃Thin-wall Stuctures Using Laser Engineered Net Shaping

Laser Engineered Net Shaping (LENS) is a new manufacturing technology, which combine laser cladding technology with rapid prototyping technology. It can fabricate a variety of complex materials efficiently. The result is a low cost, full dense, near-net-shape part. Al2O3ceramic is one of the largest ceramics production, because of its’ good performances, such as high mechanical strength, high hardness, good thermal stability, high temperature oxidation resistance ability and so on. It has been widely used in machinery, electronics, medicine, food, petroleum, chemical, aerospace, special metallurgy and other fields. The application of LENS on Al2O3ceramics not only simplify the complex parts processes, broaden the ceramic application fields, but also improve the level of hard brittle material direct forming technology. In this paper, using high purity Al2O3ceramic as forming materials, we study the impact of technological parameters (spot diameter, laser power, scanning path) on Al2O3thin-wall structures quality by LENS, and analyze the relationship between color and quality performance of thin-wall sample. Using scanning electron microscope, X-ray diffractometer, X-ray energy dispersive spectrometer detect microstructure, phase composition and chemical elements of thin-wall samples’ cross section to analyze differences among them and the causes of differences. The research contents are as follows:(1) Measure powder stream density distribution, calculate powder effective availability and analyze the impact of spot diameter on powder effective utilization. Using single-factor experiments analyze the impact of technological parameters on the surface quality of Al2O3thin-wall samples by LENS. Explore the appraisive relationship between color and quality performance. Acquire black and white Al2O3thin-wall samples’ preparation technology;(2) The microstucture of different color Al2O3thin-wall samples’ cross section is analyzed by SEM. Using XRD, EDS test phase and chemical compositions of samples’ cross section. Analyze the differences of microstucture, phase and chemical elements compositions between black and white thin-wall samples; Drainage method is used to measure different color Al2O3thin-wall samples’ volume density. Compare different color Al2O3thin-wall samples, the original ceramic powder volume density with theoretical density;(3) Analyze surface cracks of different color Al2O3thin-wall samples, and find the causes of differences. Reveal color generation mechanism of Al2O3thin-wall samples and factors which impact surface cracks and color changing. Analysis finds that center of powders stream is dense while both ends are sparse distribution, and powder effective availability increases with spot diameter increase. With increase of spot diameter, laser power and optimization of scanning path, thin-wall samples gradually turn white. And the color is more white, the performance quality of thin-wall sample is better. Forming technology of black and white Al2O3thin-wall samples change the microstructure, chemical and phase composition, and then affect samples’ volume density. Second phases are the main cause of Al2O3ceramics’ color change, and exacerbate the produce and extension of surface cracks in black thin-wall sample.