In the current research the role of samples thickness and subsequent imposed cooling rate differences has been investigated for gray cast iron in conjunction with revealing the effect of change in austempering temperature. Rectangular and wedge-shaped specimens were cut from casted bulk and subjected to an austenitizing temperature of 900 C. In the case of the rectangular samples, austempering temperatures of 380, 400, and 420 C were employed, while the wedge-shaped specimens underwent at a constant temperature of 400 C. The wedge-shaped specimens were employed to investigate variations in section size. Distinct graphite flake morphologies (A-D) emerged, contingent on section size and cooling rate. Microstructural characterization encompassed optical microscopy (OM), scanning electron microscopy (SEM), and scanning tunneling microscopy (STM). To assess the impact of heat treatment on mechanical properties, hardness tests and Charpy impact tests were executed. It was observed that austempering increased toughness while resulting in decreased hardness values with higher austempering temperatures. The correlation between the simulated model and experimental data affirmed the pivotal role of thickness in augmenting hardness.

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