Ecofriendly Water-Soluble Binders for Precision Ceramic Moulds in Aerospace Turbine Casting: Process Development and Performance Evaluation.

The paper presents the development of an ecofriendly ceramic moulding system for the precision casting of aircraft turbine components from nickel superalloys using water-soluble binders. The motivation was to eliminate hydrolysed ethyl silicate (HES) due to its environmental and occupational hazards. Two water-based binders (K + M)-Keysol (for the primary layer) and Matrixsol (for the backup layers)-were evaluated against the standard HES-based system. A comprehensive comparative analysis was conducted including microstructure, phase composition, wettability, mechanical, thermal, and gas permeability properties. The developed K + M ceramic moulds achieved a bending strength of 12.4 MPa after annealing, average surface roughness (Ra) below 5 µm, and open porosity of 29.1%, indicating excellent strength and permeability. Thermal conductivity increased from 0.3 W/mK to 2.0 W/mK between 22 °C and 1400 °C. The wetting angle of water-based binders was higher (Keysol: ~36°) compared to HES (~5°), resulting in more stable surface morphology. Gas permeability was maintained at 5.6 × 10^-9 cm² at 1100 °C, ensuring effective degassing during casting. The results demonstrate that the K + M system can replace HES in production while improving safety and reducing environmental impact, making it suitable for industrial-scale implementation in the aerospace sector.