Optimal design of high-strength water-soluble sand core for investment casting system: Thermodynamic analysis and experimental verification

The water-soluble sand cores (WSC-sand) used in the investment casting of complex three-dimensional metal parts are highly susceptible to casting defects. Our objective in this study was to optimize the fabrication process for a novel high-strength WSC-sand comprising magnesium sulfate (MgSO4) composite, based on thermodynamic analysis using a thermochemistry software package (FactSage) and experimental verification. Preliminary analyses and experiments were used to derive the optimal preparation conditions for high-strength WSC-sandMG: raw sand (equal weights of magnesia oxide and graphite), binder (2 wt% MgSO4 at a concentration of 30%), and heating temperature (200 degrees C). Subsequent experiments revealed that the optimal quantity of reinforcing agent (RA) (kaolinite) was 2 wt%. The efficacy of the fabrication process was validated by creating metal casts (SNCM220 at a casting temperature of 1600 degrees C) using two types of WSC-sand-MG-RA samples. Nondestructive radiographic testing images and photographs of the finished casting products verified the efficacy of the proposed fabrication strategy in terms of surface smoothness and inside pinholes. The results presented in this paper provide a valuable reference for the preparation of WSC-sand from the perspective of quality and cost efficiency. (C)2020 The Authors. Published by Elsevier Ltd.