Material development for laser sintering of high temperature strength silicon carbide with extrem hardness

Laser sintering is described as an efficient and successful technique for the fast and direct production of complex-shaped prototypes of technical ceramics. After presentation of the state of the art of laser sintered silicon infiltrated silicon carbide (SiSiC) the paper describes new aspects of material development. Finer raw SiC powders were used and an additional carbon dotation process was established. The significantly higher SiC/Si phase ratio in the ceramic material results in increasing the 4-point flexural strength from 196 to 267 Mpa. Laser sintering of metal powder has been used in industry for direct production of injection molding tools, models and prototypes for several years. Produced parts are distinguished by accurate dimensions and contous and can have extremely complex and filigree geometries. Undercuts and holes can be generated in the part very simply because layers are built up to produce the end part. The potential for application of laser sintered SiSiC is given by the possibility to realize prototypes very fast and efficiently as well as by the possibility to create free shaped and filigree geometries. The aim of the presented work was the improvement of the mechanical properties of laser sintered SiSiC, especially a significant improvement of their flexural strength was intended. The lower flexural strength of laser sintered SiSiC in comparison to material made conventionally by powder technology can be explained by the relatively high content of silicon in the laser sinterered material. Two silicon carbide powders with average grain sizes of 13 and 23 micrometer were used. A surprisingly wide variety of solidification mechanisms were found. Sintered agglomerates typical for metal laser sintering were rarely found.