SiC ceramic mirror fabricated by additive manufacturing with material extrusion and laser cladding

Abstract

As the aperture of the optical component increases, the integrated design of the silicon carbide optical component and the support structure will lead to a more complex structure of the silicon carbide optical component, which is difficult to achieve with traditional ceramic molding and sintering technology. In this work, a novel shaping method for the fabrication of reaction bonded silicon carbide ceramic substrate was investigated. Here, four kinds of mixture consisting of silicon carbide, carbon black powder, and organic binder with different solid loading were developed by varying the content of the lubricant paraffin wax (PW) and printed by material extrusion (MEX). The effects of solid loading on the rheological properties of mixtures, thermal expansion behavior, and morphology of the samples after debinding were studied. Similarly, two kinds of materials were prepared with silicon carbide to carbon black ratios of 50: 50 and 60: 40 under optimal solid loading, and their microstructure was analyzed and compared. The results show that reaction bonded silicon carbide ceramics with a flexural strength of 310.41 ± 39.32 MPa and a modulus of elasticity of 346.3 ± 22.80 GPa can be obtained by MEX and reactive sintering when the ratio of silicon carbide to carbon black is 60:40 and at an optimum solid loading (~60 vol%). Subsequently, the dense glass layer was prepared on the surface of 3D printed SiC by laser cladding. After polishing and plating with Ag film, it shows good reflection. In the range of 500–800 nm, the average reflectivity is higher than 97%. The laser cladding Si layer acts as a transition layer, which improves the wettability between the glass melt and the substrate and weakens the decomposition of SiC. This work provides a reference for the preparation of high precision, high strength, and high density SiC ceramic mirror by material extrusion and laser cladding.