Investigation of influence of technological parameters on the properties of SiC samples fabricated by selective laser sintering. Part 1

Abstract

The paper describes experiments on selective laser sintering (SLS) of a high-temperature ceramic material – silicon carbide powder F320 – using the MeltMaster3D-160 SLS unit equipped with a fiber ytterbium laser with a peak power of 200 W. We investigated the sintering mechanism and the impact of technological parameters on the microstructure, phase composition, and density of the resulting 3D cubic samples. The technological properties of the initial powder were also investigated, including morphology, granulometric composition, bulk density, and flow rate. The powder morphology mainly consists of acicular particles with an aspect ratio of 1:5. Granulometric analysis revealed an average particle size of 48 μm. Measurements indicated that the bulk density reached 1.11 ± 0.01 g/cm3, approximately 36.6 % of the theoretical density value. The average time of powder outflow from the Hall funnel was 21.0 ± 0.1 s, with 2–3 hits on the funnel during the measurement process. Experimental cubic samples of 10×10 mm were manufactured using 75 technological modes. Silicon carbide powder particles sinter due to the thermal effect of laser radiation and the release of SiC microparticles on the surface of the powder particles, with silicon (average size less than 1 μm) prevailing in the composition, followed by mutual bonding of neighboring powder particles in the sintering region. X-ray phase analysis demonstrated that due to the laser radiation, the resulting 3D samples contain the following phases: SiC (6H), Si, and C. It was revealed that a scanning step larger than the actual spot diameter (spot diameter + thermal influence zone), 60–70 μm in size, causes the formation of unsintered areas between sintering tracks. The key parameters affecting the density index of the obtained samples are layer height, energy density, and scanning step. The best density index for the obtained samples is 86.7 % relative to the absolute density of the material (3.21 g/cm3). Further research will be devoted to the development of techniques for post-processing the resulting porous samples-blanks to obtain a density close to 100 %.