Abstract
Lost-wax casting, also called precision casting, is the process of casting a duplicate metal sculpture cast an original sculpture. The ceramic shell mould used in lost-wax casting usually consists of several layers formed with fine zircon and granular mullite particles using silica gel as a binder. However, it is a complicated and time-consuming process. Large amounts of waste moulds that need to be disposed and recycled become an environmental concern. In this study, waste shell sand from the recycled mould and calcium carbonate/metakaolin were used as raw materials to prepare geopolymer slurry and coating. The influence of mixing ratio and the SiO2/K2O modulus of the alkali solution on the setting time and green/fired strength were evaluated. Ceramic shells with one to four layers of geopolymer slurry and waste sand sprinkling were fabricated and tested for their permeability and green/fired strength. It was found that geopolymer shells had higher green/fired strength and better permeability than the original zircon/mullite shell. For foundry practice, metal casts were fabricated using recycled ceramic shell moulds with one to four layers of geopolymer coating. All cast results have their dimensions all within tolerance limitation and up to 13 h can be saved for the preparation of shell moulds.
Highlights
Investment casting is one of the oldest manufacturing processes
In order to solve these problems, this study focuses on the recycling and reutilization the waste shell sand to produce a new ceramic shell and shorten the processing time of investment casting using the geopolymer technique
For practical application and performance evaluation, ceramic shell moulds made with geopolymer slurry and waste sand sprinkling were tested for their green/fired strength and permeability followed by metal casting and tolerance measurement
Summary
Investment casting is one of the oldest manufacturing processes. It can produce a cast of complicated shape with high precision and a smooth surface that cannot be achieved with the die casting method. In the process of investment casting, the ceramic mould, known as the investment, is produced by repeating a series of steps—coating, sprinkling, and hardening. Investment casting still has two problems that need to be solved: (1) up to 58 h of drying time is needed for the green ceramic shell after dipping in ceramic slurry [1] and (2) the disposal of waste ceramic shell moulds. In order to solve these problems, this study focuses on the recycling and reutilization the waste shell sand to produce a new ceramic shell and shorten the processing time of investment casting using the geopolymer technique. For practical application and performance evaluation, ceramic shell moulds made with geopolymer slurry and waste sand sprinkling were tested for their green/fired strength and permeability followed by metal casting and tolerance measurement
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