In order to explore the influence of weld time on joint strength, nugget size, mode of fracture of Hastelloy X weldments fabricated by resistance spot welding process, an experimental investigation is established to determine the parameters and root cause of the failure by the use of Fractography. The adequate resistance spot welding process parameters for Hastelloy X of 750 µm thickness, welding current periods of 30, 40, 50 and 60 cycles are selected in the welding process. Other parameters like squeeze time, hold time, off time and electrode force is kept fixed. Elevation in weld time led to a significant increase in weld dimension. Also, the relationships between mechanical properties and weld nugget dimensions with weld time is evaluated. Fractographic analysis is conducted using scanning electron microscopy (SEM). Macrographs demonstrated that excellent welding formed continuously along the interface, except for sample welded for 60 cycles which failed during welding. The vital results infer that the nugget diameter broadens with increasing weld time and the strength of resistance spot welded metal improves with increasing weld time up to an optimum value. Beyond an optimum value of weld time, instantaneous crack initiation takes place during welding itself due to excessive heat input and electrode pressure subjected to the metal. The observations on tensile-shear breaking load, nugget diameter, macrographs and SEM fractographs of nugget for tensile-shear application for resistance spot welding are discussed.