The work investigated the nature and features of surface strengthening of steel products during friction thermomechanical processing (FTMP) of the surface. For this purpose, changes in the structure and properties occurring under the influence of FTMP in test samples were studied, and the influence of energy parameters during FTMP on the amount of surface strengthening of the samples was also evaluated. As a result of the research work, the factors affecting the preliminary thermal strengthening and additional strengthening of 65G steel samples using FTMP were identified, which allowed to increase the microhardness of the steel in the processing zone by more than 2 times. At the same time, the microhardness was increased thermally to the level of about 580 kgf/mm2, which is equivalent to 5800 MPa, and after FTMP, the microhardness increased to 1300 kgf/mm2, which corresponds to 13000 MPa. It is also shown that the strengthened "white" layer formed during FTMP and located along their entire processing length is continuous, which characterizes the homogeneity and uniformity of the strengthening of the surface of the samples. The load distribution at FTMP was determined using a dynamometer and the circumferential force of friction processing was calculated, which made it possible to establish dependencies that show the strengthening characteristics taking into account the thickness of the friction disc. Taking these data into account, recommendations are offered regarding the optimal thickness of the reinforcing disc.