<![CDATA[This study investigates the effect of preheating temperature on the tensile strength, hardness, and microstructural characteristics of FC-25 gray cast iron welded using the Shielded Metal Arc Welding (SMAW) process with a nickel-based electrode. Four preheating conditions were examined: non-preheated, 150°C, 200°C, and 250°C. The specimens were evaluated through tensile testing, Rockwell hardness testing, and microstructural observation at 50× magnification. The results showed that preheating at 200°C produced the highest average tensile strength of 147.39 MPa and the highest elongation of 3.08%. In contrast, the lowest tensile strength and elongation were obtained at 150°C, with values of 82.87 MPa and 1.37%, respectively. The base metal hardness remained constant at 36.47 HRC across all conditions. The highest HAZ hardness was 50.67 HRC under non-preheated conditions, while the lowest was 43.30 HRC at 250°C. Similarly, weld metal hardness decreased from 28.23 HRC without preheating to 20.87 HRC at 250°C. Microstructural observations revealed relatively similar characteristics in the base metal, whereas more noticeable morphological variations occurred in the HAZ and weld metal. Overall, preheating at 200°C provided the highest tensile strength and elongation among the tested conditions, while preheating at 250°C produced the lowest hardness in the HAZ and weld metal.]]>
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