Fabrication of barium-strontium aluminosilicate coatings on C/SiC composites via laser cladding

Barium-strontium aluminosilicate (BSAS) and Si/BSAS coatings were fabricated on the surface of C/SiC composites via a two-step laser cladding process. The microstructure, mechanical properties, and the water vapor corrosion behavior of the samples were investigated. The BSAS coating was found to be tightly bonded to the substrate and only a few pores and microcracks were observed. The introduction of a silicon middle layer was revealed to reduce thermal stress and promote the healing of defects formed during the laser cladding process. To evaluate the corrosion resistance, the BSAS and Si/BSAS-coated C/SiC composites were exposed to an atmosphere of 50% H2O and 50% O2 at 1250 °C. The resulting weight change and flexural strength were measured as a function of the corrosion time. The addition of the silicon middle layer below the BSAS top layer resulted in a better resistance to water vapor corrosion. Furthermore, the Si/BSAS-coated samples showed a lower weight loss and a smaller reduction in flexural strength than the BSAS-coated and the uncoated samples during water vapor corrosion. Thus, laser cladding is demonstrated to be an effective and feasible method to fabricate high-quality ceramic coatings on C/SiC composites. The introduction of a silicon middle layer can inhibit defect formation during the laser cladding process and protect the composite from water vapor corrosion.