The machined surface of metals undergoes work-hardening. Functionally graded materials have been developed through work-hardening. Shot peening is a method in which the surface of a material is struck with media at high speed. This process is applied in the development of functionally graded materials. In a previous study, the chemical composition of the shot-peened surface of a heated material was altered by diffusion of the shot media into the surface. The chemical composition of the shot media diffused layer promoted local alloying. Furthermore, shot peening of the surface of the heated material enhanced the mechanical properties. Moreover, the metallic structure of the hot shot-peened material surface was refined. Herein, the influence of hot shot peening on the mechanical properties of steel was investigated for the development of a methodology for achieving functional gradient materials.