This study investigates the joinability of AISI 8640 heat treatable steel and AISI 304 austenitic stainless steel combined with friction welding. These steels have completely different properties and widely used in industrial applications. Welding is applied on steels with the parameters of 1800 rev/min turning speed, 50 MPa friction pressure and 2, 4, 6, 8 and 10 sec friction time by using continuously driven friction welding machine. After the welding process, tensile and hardness testing applied to determine tensile and hardness strength of welded samples. Additionally, in order to determine the microstructural features, research using the optical microscope, scanning electron microscope (SEM) with Energy-dispersive Xray spectroscopy (EDS) analysis tests were done. According to the information derived from the results, AISI 304 and AISI 8640 steels joined with friction welding without any problem