Dimensional stability during post-processing of selective laser sintered ceramic preforms

摘要

Silicon infiltrated silicon carbide parts have been manufactured using selective laser sintering (SLS). The processing route has been defined, including post-processing steps: formation of a green part from silicon carbide powder using a phenolic binder, infiltration with a transient epoxy binder, dissociation of the binders thermally to create a brown part, heating the brown part to the infiltration temperature and infiltrating with molten silicon. Following a review of infiltration in freeform fabrication with emphasis on SLS, a dimensional analysis study was performed. Cubes 25.4 mm on each side were selective laser sintered and measured after each processing step. The largest dilatation (volume strain), 7.3%, was associated with creation of the green part relative to the computer solid model. The smallest dilatation, -6%, was associated with binder dissociation shrinkage. These volume strains nominally offset, resulting in creation of non-metallic parts with small dimensional errors relative to the computer solid model.