In this study, nickel-based Inconel 718 superalloy and iron-based AISI 316L stainless steel were joined by friction welding using 27 different welding parameters. It is aimed to contribute to the literature on determining the initial length of the welded samples for similar applications to be made later by determining the axial shortening of the welded samples. Welding samples which have 12mm diameter and 70 mm length were prepared for Inconel 718 and AISI 316L. In the friction welding machine, AISI 316L stainless steel is attached to the rotating chuck and Inconel 718 superalloy is attached to the linear moving chuck. For continuous friction welding parameters, 3 different rotational speeds (1800-1600-1400 rpm), 3 different friction times for each rotational speed (16-12-6 s) and 3 different friction pressures (60-40-20 MPa), forge pressure (120-80-40 MPa) and forge time (32-24-12 s) were determined. The axial shortenings of the samples which welded with these parameters were measured with the digital caliper. As a result, the maximum axial shortening was measured as 8.57 mm in the S1 sample, and the minimum shortening was measured as 1.39 mm in the S18 sample. When the welded samples are examined in macro terms, it has been seen that the HAZ is narrower on the Inconel 718 side. When the welding specimens were examined, cracks were observed on the flash on the Inconel 718 side. It was observed that axial shortening increased as friction and forge pressure increased at 1800 rpm and 1600 rpm. In all samples, the increase in friction and forge time increased axial shortening in length.