Evaluating Thermal and Dielectric Properties of Wax Patterns and Their Effects on Ceramic Mould During the Microwave Dewaxing ProcessPages 301-313
Ahmed Omar Aswaye Amhamed Abstract:
Dewaxing process in investment casting (IC) encounters multiple challenges such as high energy consumption, mould cracking, and wax contamination. One of the contributors to mould cracks is the disparity in thermal properties between the wax pattern and green ceramic mould, which leads to defective castings. This study aims to compare the thermal and dielectric properties of the commercial investment casting wax HYFILL B289 MOD S and a new wax SIVUCH L1203 and their effects on the ceramic mould during the microwave dewaxing process. TGA and DTA analyses were conducted on both waxes, while dielectric properties were evaluated on waxes and the green ceramic mould. Additionally, the strength of the green moulds was tested. The results indicated that SIVUCH L1203 wax outperformed its counterpart, HYFILL B289 MOD S wax, owing to its thermal and absorbing properties, which are superior to meeting investment casting requirements. Specifically, SIVUCH L1203 wax demonstrated an impeccably smooth and pristine inner surface without crack at all microwave power outputs of 300, 450, 600, and 850 watts. Although the green ceramic moulds demonstrated an average flexural strength of 3.983 MPa, axial cracks were observed in these moulds under all microwave power conditions when HYFILL B289 S wax was used. This is attributed to the wax's higher melting point, which enables it to maintain structural integrity for a longer period and allows for greater expansion before undergoing thermal degradation. The variation in thermal expansion of both waxes was validated by strain gauge experiments, which concluded that cracks formed only on the HYFILL B289 MOD S moulds. Keywords: Investment casting,
Microwave heating,
Dielectric properties,
Dewaxing,
Crack
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