Comparative study of conventional and glass fiber modified ceramic shells

Abstract

ABSTRACT Investment casting (IC) is well known to produced castings with excellent surface finish quality and close dimensional accuracy. Shell cracking is the foremost cause of casting rejection in the IC process. There are many causes of shell cracking in the IC process. However, the leading cause is poor shell strength. The shells having poor strength would produce defects on the final cast part and degraded the mechanical properties of the part. In this research work, the main objective was to improve ceramic shell strength by adding glass fibers to the backup coat ceramic slurry. It can be observed that the addition of glass fibers enhanced the flexural strength of the modified shell when compared to that of the conventional shell. The highest flexural strength was exhibited by the shell, which was modified with 0.50 wt.% of glass fibers. Fiber-reinforced modified ceramic shells had a larger bonded area between the fibers modified ceramic slurry and stucco coating. FE-SEM was used to analyze the microstructure characterization. Permeability and inner layer roughness of conventional and modified shells were measured and compared with conventional shells. XRD analysis was carried out with 0.50 wt.% of glass-fibers of unfired and fired shells at 700°C, 800°C & 900°C.